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Archive   : INTER43A.ZIP
Filename : INTERRUP.D

 
Output of file : INTERRUP.D contained in archive : INTER43A.ZIP

Interrupt List, part 4 of 12
This compilation is Copyright (c) 1989,1990,1991,1992,1993,1994 Ralf Brown
--------O-20---------------------------------
INT 20 - Minix - SEND/RECEIVE MESSAGE
AX = process ID of other process
BX -> message
CX = operation (1 send, 2 receive, 3 send&receive)
Program: Minix is a Version 7 Unix-compatible operating system by Andrew
Tanenbaum
Note: the message contains the system call number (numbered as in V7
Unix(tm)) and the call parameters
--------D-20---------------------------------
INT 20 - DOS 1+ - TERMINATE PROGRAM
CS = PSP segment
Return: never
Note: (see INT 21/AH=00h)
SeeAlso: INT 21/AH=00h,INT 21/AH=4Ch
--------G-20---------------------------------
INT 20 - COMTROL HOSTESS i/ISA DEBUGGER - INVOKE FIRMWARE DEBUGGER
???
Return: ???
SeeAlso: INT 21"COMTROL"
--------G-21---------------------------------
INT 21 - COMTROL HOSTESS i/ISA DEBUGGER - GET SEGMENT FOR CONTROL PROGRAM USE
???
Return: AX = first segment available for control program use
SeeAlso: INT 20"COMTROL",INT 22"COMTROL"
--------D-2100-------------------------------
INT 21 - DOS 1+ - TERMINATE PROGRAM
AH = 00h
CS = PSP segment
Notes: Microsoft recommends using INT 21/AH=4Ch for DOS 2+
execution continues at the address stored in INT 22 after DOS performs
whatever cleanup it needs to do
if the PSP is its own parent, the process's memory is not freed; if
INT 22 additionally points into the terminating program, the
process is effectively NOT terminated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=26h,AH=31h,AH=4Ch,INT 20,INT 22
--------D-2101-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STANDARD INPUT, WITH ECHO
AH = 01h
Return: AL = character read
Notes: ^C/^Break are checked, and INT 23 executed if read
character is echoed to standard output
standard input is always the keyboard and standard output the screen
under DOS 1.x, but they may be redirected under DOS 2+
SeeAlso: AH=06h,AH=07h,AH=08h,AH=0Ah
--------D-2102-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STANDARD OUTPUT
AH = 02h
DL = character to write
Return: AL = last character output (despite the official docs which state
nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break are checked, and INT 23 executed if pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
the last character output will be the character in DL unless DL=09h
on entry, in which case AL=20h as tabs are expanded to blanks
SeeAlso: AH=06h,AH=09h
--------D-2103-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STDAUX
AH = 03h
Return: AL = character read
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
SeeAlso: AH=04h,INT 14/AH=02h,INT E0/CL=03h
--------D-2104-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STDAUX
AH = 04h
DL = character to write
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
if STDAUX is busy, this function will wait until it becomes free
SeeAlso: AH=03h,INT 14/AH=01h,INT E0/CL=04h
--------D-2105-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO PRINTER
AH = 05h
DL = character to print
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDPRN is usually the first parallel port, but may be redirected under
DOS 2+
if the printer is busy, this function will wait
SeeAlso: INT 17/AH=00h
--------D-2106-------------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE OUTPUT
AH = 06h
DL = character (except FFh)
Return: AL = character output (despite official docs which state nothing is
returned) (at least DOS 3.3-5.0)
Notes: does not check ^C/^Break
writes to standard output, which is always the screen under DOS 1.x,
but may be redirected under DOS 2+
SeeAlso: AH=02h,AH=09h
--------D-2106--DLFF-------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE INPUT
AH = 06h
DL = FFh
Return: ZF set if no character available
AL = 00h
ZF clear if character available
AL = character read
Notes: ^C/^Break are NOT checked
if the returned character is 00h, the user pressed a key with an
extended keycode, which will be returned by the next call of this
function
this function reads from standard input, which is always the keyboard
under DOS 1.x, but may be redirected under DOS 2+
although the return of AL=00h when no characters are available is not
documented, some programs rely on this behavior
SeeAlso: AH=0Bh
--------D-2107-------------------------------
INT 21 - DOS 1+ - DIRECT CHARACTER INPUT, WITHOUT ECHO
AH = 07h
Return: AL = character read from standard input
Notes: does not check ^C/^Break
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=08h,AH=0Ah
--------D-2108-------------------------------
INT 21 - DOS 1+ - CHARACTER INPUT WITHOUT ECHO
AH = 08h
Return: AL = character read from standard input
Notes: ^C/^Break are checked, and INT 23 executed if detected
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=07h,AH=0Ah,AH=64h
--------D-2109-------------------------------
INT 21 - DOS 1+ - WRITE STRING TO STANDARD OUTPUT
AH = 09h
DS:DX -> '$'-terminated string
Return: AL = 24h (the '$' terminating the string, despite official docs which
state that nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break are checked, and INT 23 is called if either pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=02h,AH=06h"OUTPUT"
--------D-210A-------------------------------
INT 21 - DOS 1+ - BUFFERED INPUT
AH = 0Ah
DS:DX -> buffer (see #0505)
Return: buffer filled with user input
Notes: ^C/^Break are checked, and INT 23 is called if either detected
reads from standard input, which may be redirected under DOS 2+
if the maximum buffer size (see #0505) is set to 00h, this call returns
immediately without reading any input
SeeAlso: AH=0Ch,INT 2F/AX=4810h

Format of DOS input buffer:
Offset Size Description (Table 0505)
00h BYTE maximum characters buffer can hold
01h BYTE (call) number of chars from last input which may be recalled
(return) number of characters actually read, excluding CR
02h N BYTEs actual characters read, including the final carriage return
--------K-210A00-----------------------------
INT 21 - WCED v1.6+ - INSTALLATION CHECK
AX = 0A00h
DS:DX -> 6-byte buffer whose first two bytes must be 00h
Return: buffer offset 02h-05h filled with "Wced" if installed
Program: WCED is a free command-line editor and history utility by Stuart
Russell
SeeAlso: AH=FFh"CED"
--------D-210B-------------------------------
INT 21 - DOS 1+ - GET STDIN STATUS
AH = 0Bh
Return: AL = status
00h if no character available
FFh if character is available
Notes: ^C/^Break are checked, and INT 23 is called if either pressed
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), this function
returns AL=FFh if a partially-formed double-byte character is
available
SeeAlso: AH=06h"INPUT",AX=4406h
--------v-210B56-----------------------------
INT 21 - VIRUS - "Perfume" - INSTALLATION CHECK
AX = 0B56h
Return: AX = 4952h if resident
SeeAlso: AX=0D20h,INT 12/AX=4350h/BX=4920h
--------D-210C-------------------------------
INT 21 - DOS 1+ - FLUSH BUFFER AND READ STANDARD INPUT
AH = 0Ch
AL = STDIN input function to execute after flushing buffer
other registers as appropriate for the input function
Return: as appropriate for the specified input function
Note: if AL is not one of 01h,06h,07h,08h, or 0Ah, the buffer is flushed but
no input is attempted
SeeAlso: AH=01h,AH=06h"INPUT",AH=07h,AH=08h,AH=0Ah
--------D-210D-------------------------------
INT 21 - DOS 1+ - DISK RESET
AH = 0Dh
Return: (DOS 6 only) CF clear (earlier versions preserve CF)
Notes: This function writes all modified disk buffers to disk, but does not
update the directory information (that is only done when files are
closed or a SYNC call is issued)
SeeAlso: AX=5D01h,INT 13/AH=00h,INT 2F/AX=1120h
--------v-210D20-----------------------------
INT 21 - VIRUS - "Crazy Imp" - INSTALLATION CHECK
AX = 0D20h
Return: AX = 1971h if resident
SeeAlso: AX=0B56h,AH=30h/DX=ABCDh
--------D-210E-------------------------------
INT 21 - DOS 1+ - SELECT DEFAULT DRIVE
AH = 0Eh
DL = new default drive (00h = A:, 01h = B:, etc)
Return: AL = number of potentially valid drive letters
Notes: under Novell NetWare, the return value is always 32, the number of
drives that NetWare supports
under DOS 3+, the return value is the greatest of 5, the value of
LASTDRIVE= in CONFIG.SYS, and the number of drives actually present
on a DOS 1.x/2.x single-floppy system, AL returns 2 since the floppy
may be accessed as either A: or B:
otherwise, the return value is the highest drive actually present
DOS 1.x supports a maximum of 16 drives, 2.x a maximum of 63 drives,
and 3+ a maximum of 26 drives
SeeAlso: AH=19h,AH=3Bh,AH=DBh
--------v-210E--DLAD-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - INSTALLATION CHECK
AH = 0Eh
DL = ADh
Return: AL = BAh if installed
Program: SDRes is the resident portion of the Search&Destroy antiviral by
Fifth Generation Systems, as bundled with Novell DOS 7
SeeAlso: AH=0Eh/DL=AEh,AH=0Eh/DL=AFh,AH=4Ah/BX=00B6h,INT 13/AX=A759h
--------v-210E--DLAE-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - CLEAR ??? FLAG
AH = 0Eh
DL = AEh
SeeAlso: AH=0Eh/DL=ADh,AH=0Eh/DL=AFh,INT 13/AX=A759h
--------v-210E--DLAF-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - SET ??? FLAG
AH = 0Eh
DL = AFh
SeeAlso: AH=0Eh/DL=ADh,AH=0Eh/DL=AEh,INT 13/AX=A759h
--------D-210F-------------------------------
INT 21 - DOS 1+ - OPEN FILE USING FCB
AH = 0Fh
DS:DX -> unopened File Control Block (see #0506)
Return: AL = status
00h successful
FFh file not found or access denied
Notes: (DOS 3.1+) file opened for read/write in compatibility mode
an unopened FCB has the drive, filename, and extension fields filled
in and all other bytes cleared
not supported by MS Windows 3.0 DOSX.EXE DOS extender
DR-DOS checks password attached with AX=4303h
BUG: APPEND for DOS 3.3+ corrupts DX if the file is not found
SeeAlso: AH=10h,AH=16h,AH=3Dh,AX=4303h

Format of File Control Block:
Offset Size Description (Table 0506)
-7 BYTE extended FCB if FFh
-6 5 BYTEs reserved
-1 BYTE file attribute if extended FCB
00h BYTE drive number (0 = default, 1 = A, etc)
01h 8 BYTEs blank-padded file name
09h 3 BYTEs blank-padded file extension
0Ch WORD current block number
0Eh WORD logical record size
10h DWORD file size
14h WORD date of last write (see #0803 at AX=5700h)
16h WORD time of last write (see #0802 at AX=5700h) (DOS 1.1+)
18h 8 BYTEs reserved (see #0507,#0508,#0509,#0510,#0511)
20h BYTE record within current block
21h DWORD random access record number (if record size is > 64 bytes, high
byte is omitted)
Note: to use an extended FCB, you must specify the address of the FFh flag at
offset -7, rather than the address of the drive number field

Format of FCB reserved field for DOS 1.0:
Offset Size Description (Table 0507)
16h WORD location in directory (if high byte = FFh, low byte is device
ID)
18h WORD number of first cluster in file
1Ah WORD current absolute cluster number on disk
1Ch WORD current relative cluster number within file
(0 = first cluster of file, 1 = second cluster, etc.)
1Eh BYTE dirty flag (00h = not dirty)
1Fh BYTE unused

Format of FCB reserved field for DOS 1.10-1.25:
Offset Size Description (Table 0508)
18h BYTE bit 7: set if logical device
bit 6: not dirty
bits 5-0: disk number or logical device ID
19h WORD starting cluster number on disk
1Bh WORD current absolute cluster number on disk
1Dh WORD current relative cluster number within file
1Fh BYTE unused

Format of FCB reserved field for DOS 2.x:
Offset Size Description (Table 0509)
18h BYTE bit 7: set if logical device
bit 6: set if open???
bits 5-0: ???
19h WORD starting cluster number on disk
1Bh WORD ???
1Dh BYTE ???
1Eh BYTE ???
1Fh BYTE ???

Format of FCB reserved field for DOS 3.x:
Offset Size Description (Table 0510)
18h BYTE number of system file table entry for file
19h BYTE attributes
bits 7,6: 00 = SHARE.EXE not loaded, disk file
01 = SHARE.EXE not loaded, character device
10 = SHARE.EXE loaded, remote file
11 = SHARE.EXE loaded, local file or device
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file---
1Ah WORD starting cluster of file on disk
1Ch WORD (DOS 3.x) offset within SHARE of sharing record
(see #0774 at AH=52h)
1Eh BYTE file attribute
1Fh BYTE ???
---SHARE.EXE loaded, remote file---
1Ah WORD number of sector containing directory entry
1Ch WORD relative cluster within file of last cluster accessed
1Eh BYTE absolute cluster number of last cluster accessed
1Fh BYTE ???
---SHARE.EXE not loaded---
1Ah BYTE (low byte of device attribute word AND 0Ch) OR open mode
1Bh WORD starting cluster of file
1Dh WORD number of sector containing directory entry
1Fh BYTE number of directory entry within sector
Note: if FCB opened on character device, DWORD at 1Ah is set to the address
of the device driver header, then the BYTE at 1Ah is overwritten.

Format of FCB reserved field for DOS 5.0:
Offset Size Description (Table 0511)
18h BYTE number of system file table entry for file
19h BYTE attributes
bits 7,6: 00 = SHARE.EXE not loaded, disk file
01 = SHARE.EXE not loaded, character device
10 = SHARE.EXE loaded, remote file
11 = SHARE.EXE loaded, local file or device
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file---
1Ah WORD starting cluster of file on disk
1Ch WORD unique sequence number of sharing record
1Eh BYTE file attributes
1Fh BYTE unused???
---SHARE.EXE loaded, remote file---
1Ah WORD network handle
1Ch DWORD network ID
---SHARE not loaded, local device---
1Ah DWORD pointer to device driver header
1Eh 2 BYTEs unused???
---SHARE not loaded, local file---
1Ah BYTE extra info
bit 7: read-only attribute from SFT
bit 6: archive attribute from SFT
bits 5-0: high bits of sector number
1Bh WORD starting cluster of file
1Dh WORD low word of sector number containing directory entry
1Fh BYTE number of directory entry within sector
--------D-2110-------------------------------
INT 21 - DOS 1+ - CLOSE FILE USING FCB
AH = 10h
DS:DX -> File Control Block (see #0506)
Return: AL = status
00h successful
FFh failed
Notes: a successful close forces all disk buffers used by the file to be
written and the directory entry to be updated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=16h,AH=3Eh
--------D-2111-------------------------------
INT 21 - DOS 1+ - FIND FIRST MATCHING FILE USING FCB
AH = 11h
DS:DX -> unopened FCB (see #0506), may contain '?' wildcards
Return: AL = status
00h successful
[DTA] unopened FCB for first matching file
FFh no matching filename, or bad FCB
Notes: the type of the returned FCB depends on whether the input FCB was a
normal or an extended FCB
the data returned in the DTA is actually the drive number (or extended
FCB header and drive number) followed by the file's directory entry
(see #0512); this format happens to be compatible with an unopened
FCB
for extended FCBs with search attribute 08h, the volume label (if any)
will be returned even if the current directory is not the root dir.
DOS 3+ also allows the '*' wildcard
the search FCB must not be modified if AH=12h will be used to continue
searching; DOS 3.3 has set the following parts of the FCB:
0Ch BYTE ???
0Dh WORD directory entry number of matching file
0Fh WORD cluster number of current directory
11h 4 BYTEs ???
15h BYTE drive number (1=A:)
this function is used by many copy protection schemes to obtain the
starting cluster of a file
SeeAlso: AH=12h,AH=1Ah,AH=4Eh,INT 2F/AX=111Bh

Format of DOS directory entry:
Offset Size Description (Table 0512)
00h 8 BYTEs blank-padded filename
08h 3 BYTEs blank-padded file extension
0Bh BYTE attributes
0Ch 10 BYTEs reserved
used by DR-DOS to store file password
16h WORD time of creation or last update (see #0802 at AX=5700h)
18h WORD date of creation or last update (see #0803 at AX=5700h)
1Ah WORD starting cluster number
1Ch DWORD file size
--------D-2112-------------------------------
INT 21 - DOS 1+ - FIND NEXT MATCHING FILE USING FCB
AH = 12h
DS:DX -> unopened FCB (see #0506)
Return: AL = status
00h successful
[DTA] = unopened FCB
FFh no more matching filenames
Note: (see AH=11h)
assumes that successful FindFirst executed on search FCB before call
SeeAlso: AH=1Ah,AH=4Fh,INT 2F/AX=111Ch
--------D-2113-------------------------------
INT 21 - DOS 1+ - DELETE FILE USING FCB
AH = 13h
DS:DX -> unopened FCB (see #0506), filename filled with template for
deletion ('?' wildcards allowed)
Return: AL = status
00h one or more files successfully deleted
FFh no matching files or all were read-only or locked
Notes: DOS 1.25+ deletes everything in the current directory (including
subdirectories) and sets the first byte of the name to 00h (entry
never used) instead of E5h if called on an extended FCB with
filename '???????????' and bits 0-4 of the attribute set (bits 1 and
2 for DOS 1.x). This may have originally been an optimization to
minimize directory searching after a mass deletion (DOS 1.25+ stop
the directory search upon encountering a never-used entry), but can
corrupt the filesystem under DOS 2+ because subdirectories are
removed without deleting the files they contain.
currently-open files should not be deleted
MS-DOS allows deletion of read-only files with an extended FCB, whereas
Novell NetWare does not
SeeAlso: AH=41h,INT 2F/AX=1113h
--------D-2114-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL READ FROM FCB FILE
AH = 14h
DS:DX -> opened FCB (see #0506)
Return: AL = status
00h successful
01h end of file (no data)
02h segment wrap in DTA
03h end of file, partial record read
[DTA] = record read from file
Notes: reads a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if a partial record was read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=15h,AH=1Ah,AH=3Fh,INT 2F/AX=1108h
--------D-2115-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL WRITE TO FCB FILE
AH = 15h
DS:DX -> opened FCB (see #0506)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: writes a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if less than a full sector is written, the data is placed in a DOS
buffer to be written out at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=14h,AH=1Ah,AH=40h,INT 2F/AX=1109h
--------D-2116-------------------------------
INT 21 - DOS 1+ - CREATE OR TRUNCATE FILE USING FCB
AH = 16h
DS:DX -> unopened FCB (see #0506), wildcards not allowed
Return: AL = status
00h successful
FFh directory full or file exists and is read-only or locked
Notes: if file already exists, it is truncated to zero length
if an extended FCB is used, the file is given the attribute in the
FCB; this is how to create a volume label in the disk's root dir
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=10h,AH=3Ch
--------D-2117-------------------------------
INT 21 - DOS 1+ - RENAME FILE USING FCB
AH = 17h
DS:DX -> modified FCB (see also #0506)
the old filename ('?' wildcards OK) is in the standard location
while the new filename ('?' wildcards OK) is stored in the 11
bytes beginning at offset 11h
Return: AL = status
00h successfully renamed
FFh no matching files,file is read-only, or new name already exists
Notes: subdirectories may be renamed using an extended FCB with the
appropriate attribute, as may volume labels
DR-DOS checks password attached with AX=4303h before permitting rename
SeeAlso: AH=0Fh,AH=13h,AX=4303h,AH=56h,INT 2F/AX=1111h
--------D-2118-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 18h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of logged drives",
which is meaningless under MS-DOS
SeeAlso: AH=1Dh,AH=1Eh,AH=20h,AX=4459h,INT 60/DI=0513h
--------D-2119-------------------------------
INT 21 - DOS 1+ - GET CURRENT DEFAULT DRIVE
AH = 19h
Return: AL = drive (00h = A:, 01h = B:, etc)
Note: Novell NetWare uses the fact that DOS 2.x COMMAND.COM issues this call
from a particular location every time it starts a command to
determine when to issue an automatic EOJ
SeeAlso: AH=0Eh,AH=47h,AH=BBh
--------D-211A-------------------------------
INT 21 - DOS 1+ - SET DISK TRANSFER AREA ADDRESS
AH = 1Ah
DS:DX -> Disk Transfer Area (DTA)
Notes: the DTA is set to PSP:0080h when a program is started
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=11h,AH=12h,AH=2Fh,AH=4Eh,AH=4Fh
--------D-211B-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR DEFAULT DRIVE
AH = 1Bh
Return: AL = sectors per cluster (allocation unit)
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see #0513)
Note: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
SeeAlso: AH=1Ch,AH=36h

(Table 0513)
Values for media ID byte:
FFh floppy, double-sided, 8 sectors per track (320K)
FEh floppy, single-sided, 8 sectors per track (160K)
FDh floppy, double-sided, 9 sectors per track (360K)
FCh floppy, single-sided, 9 sectors per track (180K)
F9h floppy, double-sided, 15 sectors per track (1.2M)
F8h hard disk
F0h other
--------D-211C-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR SPECIFIC DRIVE
AH = 1Ch
DL = drive (00h = default, 01h = A:, etc)
Return: AL = sectors per cluster (allocation unit), or FFh if invalid drive
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see #0513)
Notes: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
on a DBLSPACE drive, the total number of clusters is based on the
estimated compression ratio
SeeAlso: AH=1Bh,AH=36h
--------D-211D-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Dh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of read-only
drives", which is meaningless under MS-DOS
SeeAlso: AH=18h,AH=1Eh,AH=20h,AX=4459h
--------D-211E-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Eh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "set file attributes" which was
meaningless under MS-DOS 1.x
SeeAlso: AH=18h,AH=1Dh,AH=20h
--------D-211F-------------------------------
INT 21 - DOS 1+ - GET DRIVE PARAMETER BLOCK FOR DEFAULT DRIVE
AH = 1Fh
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) (see #0514 for DOS 1.x,
AH=32h for DOS 2+)
FFh invalid drive
Note: this call was undocumented prior to the release of DOS 5.0; however,
only the DOS 4+ version of the DPB has been documented
SeeAlso: AH=32h

Format of DOS 1.1 and MS-DOS 1.25 drive parameter block:
Offset Size Description (Table 0514)
00h BYTE sequential device ID
01h BYTE logical drive number (0=A:)
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD starting sector number of first FAT
08h BYTE number of copies of FAT
09h WORD number of directory entries
0Bh WORD number of first data sector
0Dh WORD highest cluster number (number of data clusters + 1)
0Fh BYTE sectors per FAT
10h WORD starting sector of directory
12h WORD address of allocation table
Note: the DOS 1.0 table is the same except that the first and last fields
are missing; see INT 21/AH=32h for the DOS 2+ version
--------D-2120-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 20h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get/set default user
(sublibrary) number", which is meaningless under MS-DOS
SeeAlso: AH=18h,AH=1Dh,AH=1Eh,AX=4459h
--------D-2121-------------------------------
INT 21 - DOS 1+ - READ RANDOM RECORD FROM FCB FILE
AH = 21h
DS:DX -> opened FCB (see #0506)
Return: AL = status
00h successful
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial record read
[DTA] = record read from file
Notes: the record is read from the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after reading the record
if a partial record is read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=14h,AH=22h,AH=27h,AH=3Fh
--------D-2122-------------------------------
INT 21 - DOS 1+ - WRITE RANDOM RECORD TO FCB FILE
AH = 22h
DS:DX -> opened FCB (see #0506)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: the record is written to the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after writing the record
if the record is located beyond the end of the file, the file is
extended but the intervening data remains uninitialized
if the record only partially fills a disk sector, it is copied to a
DOS disk buffer to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=15h,AH=21h,AH=28h,AH=40h
--------D-2123-------------------------------
INT 21 - DOS 1+ - GET FILE SIZE FOR FCB
AH = 23h
DS:DX -> unopened FCB (see #0506), wildcards not allowed
Return: AL = status
00h successful (matching file found)
FCB random record field filled with size in records, rounded up
to next full record
FFh failed (no matching file found)
Notes: not supported by MS Windows 3.0 DOSX.EXE DOS extender
MS-DOS returns nonsense if the FCB record number field is set to a very
large positive number, and status FFh if negative; DR-DOS returns the
correct file size in both cases
BUG: APPEND for DOS 3.3+ corrupts DX if the file is not found
SeeAlso: AH=42h
--------D-2124-------------------------------
INT 21 - DOS 1+ - SET RANDOM RECORD NUMBER FOR FCB
AH = 24h
DS:DX -> opened FCB (see #0506)
Notes: computes the random record number corresponding to the current record
number and record size, then stores the result in the FCB
normally used when switching from sequential to random access
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=27h,AH=42h
--------D-2125-------------------------------
INT 21 - DOS 1+ - SET INTERRUPT VECTOR
AH = 25h
AL = interrupt number
DS:DX -> new interrupt handler
Notes: this function is preferred over direct modification of the interrupt
vector table
some DOS extenders place an API on this function, as it is not
directly meaningful in protected mode
under DR-DOS 5.0+, this function does not use any of the DOS-internal
stacks and may thus be called at any time
Novell NetWare (except the new DOS Requester) monitors the offset of
any INT 24 set, and if equal to the value at startup, substitutes
its own handler to allow handling of network errors; this introduces
the potential bug that any program whose INT 24 handler offset
happens to be the same as COMMAND.COM's will not have its INT 24
handler installed
SeeAlso: AX=2501h,AH=35h
--------E-212501-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - RESET DOS EXTENDER DATA STRUCTURES
AX = 2501h
SS = application's original SS or DS (FlashTek X-32VM)
Return: CF clear if successful
CF set on error
caller is operating on X-32 stack (FlashTek X-32VM)
Notes: Phar Lap uses INT 21/AH=25h as the entry point for all 386/DOS-Extender
system calls. Only available when directly using 386/DOS-Extender or
a compatible DOS extender, or when using a product that was created
using 386-DOS/Extender or a compatible
this function is also supported by FlashTek X-32VM
SeeAlso: AH=30h"Phar Lap"
--------E-212502-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET PROTECTED-MODE INTERRUPT VECTOR
AX = 2502h
CL = interrupt number
Return: CF clear
ES:EBX = CS:EIP of protected-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0204h
--------E-212503-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET REAL-MODE INTERRUPT VECTOR
AX = 2503h
CL = interrupt number
Return: CF clear
EBX = CS:IP of real-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2504h,AH=35h,INT 31/AX=0200h
--------E-212504-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET PROTECTED-MODE INTERRUPT VECTOR
AX = 2504h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2505h,INT 31/AX=0205h
--------E-212505-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET REAL-MODE INTERRUPT VECTOR
AX = 2505h
CL = interrupt number
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0201h
--------E-212506-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET INT TO ALWAYS GAIN CNTRL IN PR. MODE
AX = 2506h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Notes: this function modifies both the real-mode low-memory interrupt
vector table and the protected-mode Interrupt Descriptor Table (IDT)
interrupts occurring in real mode are resignaled in protected mode
this function is also supported by FlashTek X-32VM
--------E-212507-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET REAL- & PROTECTED-MODE INT VECTORS
AX = 2507h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Notes: interrupts are disabled until both vectors have been modified
this function is also supported by FlashTek X-32VM
SeeAlso: AX=2504h,AX=2505h
--------E-212508-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET SEGMENT LINEAR BASE ADDRESS
AX = 2508h
BX = segment selector
Return: CF clear if successful
ECX = linear base address of segment
CF set if invalid segment selector
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2509h
--------E-212509-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CONVERT LINEAR TO PHYSICAL ADDRESS
AX = 2509h
EBX = linear address to convert
Return: CF clear if successful
ECX = physical address (carry flag clear)
CF set if linear address not mapped in page tables
SeeAlso: AX=2508h
--------E-212509-----------------------------
INT 21 P - FlashTek X-32VM - GET SYSTEM SEGMENTS AND SELECTORS
AX = 2509h
Return: CF clear
EAX high word = default DS
AX = alias for 16-bit data segment
BX = real mode code segment
EDX high word = selector covering full 4GB address space
DX = default SS
ESI high word = PSP selector
SI = environment selector
--------E-21250A-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - MAP PHYSICAL MEMORY AT END OF SEGMENT
AX = 250Ah
ES = segment selector in the Local Descriptor Table (LDT) of segment
to modify
EBX = physical base address of memory to map (multiple of 4K)
ECX = number of physical 4K pages to map
Return: CF clear if successful
EAX = 32-bit offset in segment of mapped memory
CF set on error
EAX = error code
08h insufficient memory to create page tables
09h invalid segment selector
SeeAlso: INT 31/AX=0800h
--------E-21250C-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET HARDWARE INTERRUPT VECTORS
AX = 250Ch
Return: CF clear
AL = base interrupt vector for IRQ0-IRQ7
AH = base interrupt vector for IRQ8-IRQ15
BL = interrupt vector for BIOS print screen function (Phar Lap only)
Note: this function is also supported by FlashTek X-32VM
SeeAlso: INT 31/AX=0400h,INT 67/AX=DE0Ah
--------E-21250D-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET REAL-MODE LINK INFORMATION
AX = 250Dh
Return: CF clear
EAX = CS:IP of real-mode callback procedure (see #0515) that will
call through from real mode to a protected-mode routine
EBX = 32-bit real-mode address of intermode call data buffer
ECX = size in bytes of intermode call data buffer
ES:EDX = protected-mode address of intermode call data buffer
Notes: this function is also supported by FlashTek X-32VM
X-32VM guarantees the intermode buffer to be at least 4 KB
SeeAlso: AX=250Eh

(Table 0515)
Call Phar Lap real-mode callback with:
STACK: DWORD offset to protected-mode code
WORD placeholder for protected-mode CS
DWORD pointer to selector structure (see #0516)
or 0000h:0000h for defaults
var parameters for protected-mode procedure
Return: via FAR return

Format of Phar Lap selector structure:
Offset Size Description (Table 0516)
00h WORD protected-mode GS selector
02h WORD protected-mode FS selector
04h WORD protected-mode ES selector
06h WORD protected-mode DS selector
--------E-21250E-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE
AX = 250Eh
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy from protected-mode stack
to real-mode stack
Return: CF clear if successful
all segment registers unchanged
all general registers contain values set by real-mode procedure
all other flags set as they were left by real-mode procedure
stack unchanged
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: this function is also supported by FlashTek X-32VM; under X-32VM, the
call will fail if ECX > 0000003Fh
SeeAlso: AX=250Dh,AX=2510h,AH=E1h"OS/286",INT 31/AX=0301h
--------E-21250F-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CONVERT PROTECTED-MODE ADDRESS TO MS-DOS
AX = 250Fh
ES:EBX = 48-bit protected-mode address to convert
ECX = 00000000h or length of data in bytes
Return: CF clear if successful (address < 1MB and contiguous)
ECX = 32-bit real-mode MS-DOS address
CF set on error (address >= 1MB or not contiguous)
ECX = linear address
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2510h
--------E-212510-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE, REGISTERS
AX = 2510h
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy to protected-mode stack to
real-mode stack
DS:EDX -> pointer to parameter block (see #0517)
Return: CF clear if successful
all segment registers unchanged,
EDX unchanged
all other general registers contain values set by real-mode proc
all other flags are set as they were left by real-mode procedure
real-mode register values are returned in the parameter block
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: unlike most of the preceding 25xxh functions, this one is not
supported by FlashTek X-32VM
SeeAlso: AX=250Eh,AX=250Fh

Format of Phar Lap real-mode call parameter block:
Offset Size Description (Table 0517)
00h WORD real-mode DS value
02h WORD real-mode ES value
04h WORD real-mode FS value
06h WORD real-mode GS value
08h DWORD real-mode EAX value
0Ch DWORD real-mode EBX value
10h DWORD real-mode ECX value
14h DWORD real-mode EDX value
--------E-212511-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - ISSUE REAL-MODE INTERRUPT
AX = 2511h
DS:EDX -> parameter block (see #0518)
Return: all segment registers unchanged
EDX unchanged
all other registers contain values set by the real-mode int handler
the flags are set as they were left by the real-mode interrupt handler
real-mode register values are returned in the parameter block
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2505h,AX=250Eh,AH=E3h"OS/286",INT 31/AX=0300h

Format of Phar Lap real-mode interrupt parameter block:
Offset Size Description (Table 0518)
00h WORD interrupt number
02h WORD real-mode DS value
04h WORD real-mode ES value
06h WORD real-mode FS value
08h WORD real-mode GS value
0Ah DWORD real-mode EAX value
0Eh DWORD real-mode EDX value
Note: all other real-mode values set from protected-mode registers
--------E-212512-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - LOAD PROGRAM FOR DEBUGGING
AX = 2512h
DS:EDX -> pointer to ASCIZ program name
ES:EBX -> pointer to parameter block (see #0520)
ECX = size in bytes of LDT buffer
Return: CF clear if successful
EAX = number of segment descriptors in LDT
CF set on error
EAX = error code (see #0519)
SeeAlso: AX=2517h

(Table 0519)
Values for Phar Lap error code:
02h file not found or path invalid
05h access denied
08h insufficient memory
0Ah environment invalid
0Bh invalid file format
80h LDT too small

Format of Phar Lap program load parameter block:
Offset Size Description (Table 0520)
Input:
00h DWORD 32-bit offset of environment string
04h WORD segment of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment of command-tail string
0Ch DWORD 32-bit offset of LDT buffer (size in ECX)
10h WORD segment of LDT buffer
Output:
12h WORD real-mode paragraph address of PSP (see also AH=26h)
14h WORD real/protected mode flag
0000h real mode
0001h protected mode
16h DWORD initial EIP value
1Ah WORD initial CS value
1Ch DWORD initial ESP value
20h WORD initial SS value
22h WORD initial DS value
24h WORD initial ES value
26h WORD initial FS value
28h WORD initial GS value
--------E-212513-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - ALIAS SEGMENT DESCRIPTOR
AX = 2513h
BX = segment selector of descriptor in GDT or LDT
CL = access-rights byte for alias descriptor
CH = use-type bit (USE16 or USE32) for alias descriptor
Return: CF clear if successful
AX = segment selector for created alias
CF set on error
EAX = error code
08h insufficient memory (can't grow LDT)
09h invalid segment selector in BX
--------E-212514-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CHANGE SEGMENT ATTRIBUTES
AX = 2514h
BX = segment selector of descriptor in GDT or LDT
CL = new access-rights byte
CH = new use-type bit (USE16 or USE32)
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid selector in BX
SeeAlso: AX=2515h,INT 31/AX=0009h
--------E-212515-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET SEGMENT ATTRIBUTES
AX = 2515h
BX = segment selector of descriptor in GDT or LDT
Return: CF clear if successful
CL = access-rights byte for segment
CH = use-type bit (USE16 or USE32)
ECX<16-31> destroyed
CF set on error
EAX = error code
09h invalid segment selector in BX
SeeAlso: AX=2514h
--------E-212516-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v2.2+ - FREE ALL MEMORY OWNED BY LDT
AX = 2516h
Return: CF clear
Note: this function must be called from Ring 0 or the CS descriptor is freed
--------E-212517-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v2.1c+ - GET INFO ON DOS DATA BUFFER
AX = 2517h
Return: CF clear
ES:EBX -> data buffer (protected mode address)
ECX -> data buffer (real mode address)
EDX = size of data buffer in bytes
Note: the data buffer's address changes after calls to AX=2512h and AX=252Ah
SeeAlso: AX=2512h,AX=252Ah,AX=2530h
--------E-212518-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender 2.1c+ - SPECIFY HANDLER FOR MOVED SEGMENTS
AX = 2518h
ES:EBX -> function to call when a segment is moved
Return: CF clear
ES:EBX -> previous handler
--------E-212519-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - GET ADDITIONAL MEMORY ERROR INFO
AX = 2519h
Return: CF clear
EAX = error code
0000h no error
0001h out of physical memory
0002h out of swap space (unable to grow swap file)
0003h out of LDT entries and unable to grow LDT
0004h unable to change extended memory allocation mark
FFFFFFFFh paging disabled
Note: VMM is the Virtual Memory Manager option
--------E-21251A-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - LOCK PAGES IN MEMORY
AX = 251Ah
EDX = number of 4k pages to lock
if BL = 00h
ECX = linear address of first page to lock
if BL = 01h
ES:ECX -> pointer to first page to lock
Return: CF clear if successful
CF set on error
EAX = error code
08h insufficient memory
09h invalid address range
SeeAlso: AX=251Bh,AX=EB06h,INT 31/AX=0600h
--------E-21251B-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - UNLOCK PAGES
AX = 251Bh
EDX = number of pages to unlock
if BL = 00h
ECX = linear address of first page to unlock
if BL = 01h
ES:ECX -> pointer to first page to unlock
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address range
SeeAlso: AX=251Ah,AX=EB07h,INT 31/AX=0601h
--------E-21251C-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.1c+ - FREE PHYSICAL MEMORY PAGES
AX = 251Ch
BH = preservation flag (00h preserve contents, 01h discard contents)
EDX = number of pages to free
BL = address type
00h linear address
ECX = linear address of first page to be freed
01h pointer
ES:ECX -> first page to be freed
Return: CF clear if successful
CF set on error
EAX = error code
08h memory error, swap space full, no VMM or DPMI
09h invalid address
--------E-21251D-----------------------------
INT 21 OP - Phar Lap 386/DOS-Extender VMM v2.1c - READ PAGE-TABLE ENTRY
AX = 251Dh
BL = address type
00h linear address
ECX = linear address of page table entry to read
01h pointer
ES:ECX -> page table entry to read
Return: CF clear if successful
EAX = contents of page table entry
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
78h invalid under DPMI
Note: this function is obsolete; use AX=252Bh/BH=09h instead
SeeAlso: AX=251Eh,AX=252Bh/BH=09h,AX=EB00h,INT 31/AX=0506h
--------E-21251E-----------------------------
INT 21 OP - Phar Lap 386/DOS-Extender VMM v2.1c - WRITE PAGE-TABLE ENTRY
AX = 251Eh
BL = address type
00h linear address
ECX = linear address of page table entry to read
01h pointer
ES:ECX -> page table entry to read
EDX = new value for page table entry
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
82h not compatible with DPMI
Note: this call is obsolete; use AX=252Bh/BH=0Ah instead
SeeAlso: AX=251Dh,AX=252Bh/BH=0Ah,INT 31/AX=0507h
--------E-21251F-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - EXHANGE TWO PAGE-TABLE ENTRIES
AX = 251Fh
BL = address type
00h linear address
ECX = linear address of first page table entry
EDX = linear address of second page table entry
01h pointer
ES:ECX -> first page table entry
ES:EDX -> second page table entry
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
82h not compatible with DPMI
SeeAlso: AX=251Dh,AX=251Eh
--------E-212520-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - GET MEMORY STATISTICS
AX = 2520h
DS:EDX -> pointer to buffer at least 100 bytes in size (see #0521)
BL = 0 (don't reset VM stats), 1 (reset VM stats)
Return: carry flag clear

Format of Phar Lap VM statistics buffer:
Offset Size Description (Table 0521)
00h DWORD VM status
0001h VM subsystem is present
0000h VM not present
04h DWORD "nconvpg" number of conventional memory pages available
08h DWORD "nbimpg" number of Compaq built-in memory pages available
0Ch DWORD "nextpg" total number of extended memory pages
10h DWORD "extlim" extender memory pages limit
14h DWORD "aphyspg" number of physical memory pages allocated to appl
18h DWORD "alockpg" number of locked pages owned by application
1Ch DWORD "sysphyspg" number physical memory pages allocated to system
20h DWORD "nfreepg" number of free physical pages; approx if EMS VCPI
24h DWORD linear address of beginning of application address space
28h DWORD linear address of end of application address space
2Ch DWORD number of seconds since last time VM stats were reset
30h DWORD number of page faults since last time
34h DWORD number of pages written to swap file since last time
38h DWORD number of reclaimed pages (page faults on swapped pages)
3Ch DWORD number of virtual pages allocated to the application
40h DWORD size in pages of swap file
44h DWORD number of system pages allocated with EMS calls
48h DWORD minimum number of conventional memory pages
4Ch DWORD maximum size in pages to which swap file can be increased
50h DWORD "vmflags"
bit 0 = 1 if page fault in progress
---v4.0+ ---
54h DWORD number of physical pages guaranteed to be free
58h DWORD number of free physical pages currently available
5Ch DWORD size in pages of largest free block of memory (including disk
swap space)
60h DWORD reserved
--------E-212521-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S EXTENDED MEM USAGE
AX = 2521h
EBX = max 4k pages of physical extended memory which program may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2522h
--------E-212522-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - SPECIFY ALTERNATE PAGE-FAULT HANDLR
AX = 2522h
ES:EBX -> alternate handler for page faults
Return: CF clear
ES:EBX -> previous page-fault handler
SeeAlso: AX=2523h
--------E-212523-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - SPECIFY OUT-OF-SWAP-SPACE HANDLER
AX = 2523h
???
Return: ???
Note: this function takes a DWORD pointer and a DWORD pointer to a DWORD
pointer as arguments
SeeAlso: AX=2522h
--------E-212524-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - INSTALL PAGE-REPLACEMENT HANDLERS
AX = 2524h
???
Return: ???
Note: this function takes three DWORD pointers and three DWORD pointers to
DWORD pointers as arguments
--------E-212525-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S CONVENT'L MEM USAGE
AX = 2525h
EBX = limit in 4k pages of physical conventional memory which program
may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2521h
--------E-212526-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET CONFIGURATION INFORMATION
AX = 2526h
???
Return: ???
Notes: details are not yet available
this function takes a pointer to the configuration buffer (see #0522)
and a poitner to a BYTE as arguments

Format of Phar Lap configuration buffer:
Offset Size Description (Table 0522)
00h DWORD flags 1 (see #0523)
04h DWORD flags 2 (unused through v5.0)
08h DWORD flags 3 (unused through v5.0)
0Ch DWORD 386|DOS-Extender major version
10h DWORD 386|DOS-Extender minor version
14h DWORD first letter of text after minor version number in version str
18h DWORD beta flag (00h normal release, 01h beta release)
1Ch DWORD processor (3 = 386, 4 = 486)
20h DWORD coprocessor (4 = none, 6 = 287, 7 = 387/486)
24h DWORD Weitek coprocessor flag (0 = none, 1 = present)
28h DWORD machine type (0 = IBM PC compatible, 1 = NEC 9800 series)
2Ch DWORD machine class
IBM: bus type (0=ISA, 1=MCA, 2=XT, 3=EISA)
NEC: 0=normal mode, 1=high-res mode
30h DWORD VCPI flag (0 = none, 1 = present)
34h DWORD -WEITEK/-1167 switch (0 = AUTO, 1 = ON, 2 = OFF)
38h DWORD -MINREAL setting
3Ch DWORD -MAXREAL setting
40h DWORD -MINIBUF setting
44h DWORD -MAXIBUF setting
48h DWORD size in bytes of DOS call data buffer
4Ch DWORD number of interrupt stacks (-NISTACK)
50h DWORD interrupt stack size (-ISTKSIZE)
54h DWORD -REALBREAK setting
58h DWORD -CALLBUFS
5Ch DWORD -HWIVEC
60h DWORD -PRIVEC
64h DWORD -INTMAP
68h DWORD -PRIMAP
6Ch DWORD VCPI: master 8259 interrupt vector base (IRQ0 mapping)
70h DWORD VCPI: slave 8259 interrupt vector base (IRQ8 mapping)
74h DWORD BIOS print screen interrupt vector (0 if NEC)
78h DWORD -EXTLOW setting
7Ch DWORD -EXTHIGH setting
80h DWORD lowest physical extended-memory address allocatable
84h DWORD highest physical extended-memory address allocatable + 1
88h DWORD special memory's physical base address (00000000h if none)
8Ch DWORD special memory size in bytes (00000000h if none)
90h DWORD -MAXVCPIMEM setting
94h DWORD -VSCAN
98h DWORD -SWAPCHK (0 = OFF, 1 = ON, 2 = FORCE, 3 = MAX)
9Ch DWORD -CODESIZE setting
A0h DWORD minimum swap file size (-MINSWFSIZE)
A4h DWORD maximum swap fiel size (-MAXSWFSIZE)
A8h DWORD page replacement policy (0 = LFU, 1 = NUR)
ACh DWORD number of GDT entries (-NGDTENT)
B0h DWORD number of LDT entries (-NLDTENT)
B4h DWORD program's privilege level (0-3)
---386|DOS-Extender v3.0+ ---
B8h DWORD -LOCKSTACK setting
BCh DWORD -MAXEXTMEM
C0h DWORD -MAXXMSMEM
C4h DWORD -MAXPGMMEM
C8h DWORD -DATATHRESHOLD
CCh DWORD virtual memory manager flag (0 = not present, 1 = present)
D0h DWORD Cyrix coprocessor flag (0 = no Cyrix EMC387, 1 = present)
D4h DWORD -CYRIX setting (0 = AUTO, 1 = ON, 2 = OFF)
D8h DWORD DPMI flag (0 = not present, 1 = present)
DCh DWORD DPMI major version
E0h DWORD DPMI minor version
E4h DWORD DPMI capabilities flags (see #0524)
E8h DWORD VCPI major version
ECh DWORD VCPI minor version
F0h WORD VCPI: IRQ0-7 physical base interrupt vector
F2h WORD VCPI: IRQ8-15 physical base interrupt vector
F4h DWORD XMS flag (0 = none, 1 = present)
F8h DWORD XMS major version
FCh DWORD XMS minor version
100h WORD application's CS selector
102h WORD application's DS selector
104h WORD application's PSP selector
106h WORD application's environment selector
108h WORD selector mapping entire first megabyte
10Ah WORD selector mapping text video memory
10Ch WORD selector mapping video memory (text for IBM, graphics for NEC)
10Eh WORD selector mapping Weitek address space, 0000h if not present
110h WORD selector mapping Cyrix EMC387 address space, 0000h if none
112h WORD reserved (0)
114h DWORD real-mode FAR entry point to call to switch to protected mode
with no saved context
118h DWORD size of LDT in bytes
---386|DOS-Extender v5.0+ ---
11Ch DWORD Windows flag (0 = not present, 1 = Windows present)
120h DWORD Windows major version
124h DWORD Windows minor version
128h DWORD Windows mode (0 = real/standard, 1 = enhanced)
12Ch DWORD OS/2 flag (0 = not present, 1 = OS/2 present)
130h DWORD OS/2 major version
134h DWORD OS/2 minor version
138h 50 DWORDs reserved (0)

Bitfields for flags 1:
Bit(s) Description (Table 0523)
0 -NOPAGE specified
1 -A20 specified
2 -VDISK specified
3 -XT specified
4 -AT specified
5 -MCA specified
6 -EISA specified
7 -NORMRES specified (NEC only)
8 -HIGHRES specified (NEC only)
9 set if -SWFGROW1ST, clear if -NOSWFGROW1ST
10 -NOVM specified
11 -SAVEREGS specified
12 unused (clear)
13 -NOVCPI specified
14 -NOMUL specified
15 -NOBMCHK specified
16 -NOSPCLMEM or -NOBIM
17 -NOPGEXP specified
18 -SWAPDEFDISK specified
---v3.0+ ---
19 -SAVEINTS specified
20 -NOLOAD specified
21 -PAGELOG specified
22 -OPENDENY specified
23 -ERRATA17 specified
---v4.1+ ---
24 -NESTDPMI specified
25 -NONESTDPMI specified
26 -NODPMI specified
27 -NOPCDWEITEK specified
---v4.2+ ---
28 -WININT21 specified

Bitfields for DPMI capabilities flags:
Bit(s) Description (Table 0524)
0 paging supported
1 physical device mapping
2 conventional memory mapping
3 exceptions restartable
--------E-212527-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - EN/DISABLE STATE SAVE ON INTERRUPTS
AX = 2527h
EBX = new status (00h disabled, 01h enabled)
Return: CF clear
EBX = previous state save flag
SeeAlso: AX=2528h
--------E-212528-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - READ REGISTERS AFTER CTRL-C INT
AX = 2528h
DS:EBX -> buffer for registers (see #0525)
Return: CF clear if successful
DS:EBX buffer filled
CF set on error
EAX = error code
83h interrupt state save not enabled
84h no active interrupt
SeeAlso: AX=2527h

Format of Phar Lap buffer for registers:
Offset Size Description (Table 0525)
00h 8 BYTEs unused
08h 4 DWORDs EAX,EBX,ECX,EDX
18h 4 DWORDs ESI,EDI,EBP,ESP
28h 6 WORDs CS,DS,SS,ES,FS,GS
34h DWORD EIP
38h DWORD EFLAGS
--------E-212529-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - LOAD FLAT MODEL .EXP or .REX FILE
AX = 2529h
???
Return: ES:EBX -> parameter block (see #0526)
???
Note: details not available at this time
SeeAlso: AX=252Ah

Format of Phar Lap program load parameter block:
Offset Size Description (Table 0526)
00h DWORD initial EIP
04h WORD initial CS
06h DWORD initial ESP
0Ah WORD initial SS
0Ch 4 WORDs initial DS, ES, FS, GS
14h DWORD minimum size in bytes of program segment
18h DWORD bytes of additional memory allocated
1Ch DWORD flags
bit 0: child linked with -UNPRIVILEGED
---v6.0+ ---
bit 1: child is PE file instead of .EXP
bit 2: loaded file is a DLL
bits 3-31 reserved
---v6.0+ ---
20h DWORD module handles (PE files only)
24h 7 DWORDs reserved (0)
--------E-21252A-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - NEW LOAD PROGRAM FOR DEBUG
AX = 252Ah
DS:EDX -> ASCIZ program name
ES:EBX -> parameter block (see #0520)
ECX = size of LDT buffer in bytes
ESI = bit flags
bit 0: allow demand paging rather than loading entire program
bit 1: demand page from swap file rather than from .EXP
Return: CF clear if successful
EAX = VMM handle or FFFFFFFFh if none
ECX = number of descriptors in LDT buffer
CF set on error
EAX = error code
02h file error
EBX = file error code (see #0527)
ECX = DOS error code if EBX=1,2,3, or 8
08h insufficient memory
EBX = memory error code (see #0528)
80h LDT buffer too small
87h called twice without intervening call to AX=2531h
SeeAlso: AX=2512h,AX=2517h,AX=2529h,AX=2531h

(Table 0527)
Values for Phar Lap file error code:
01h DOS open error
02h DOS seek error
03h DOS read error
04h not an .EXP or .REX file
05h invalid file format
06h -OFFSET is not a multiple of 64K
07h -NOPAGE incompatible with -REALBREAK/-OFFSET
08h DOS error loading .EXE file

(Table 0528)
Values for Phar Lap memory error code:
01h out of physical memory
02h out of swap space
04h unable to change extended memory allocation
05h -MAXPGMMEM exceeded
06h insufficient low memory to REALBREAK value
07h insufficient low memory for PSP and environment
--------E-21252BBH00-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE UNMAPPED PAGES
AX = 252Bh
BH = 00h
???
Return: ???
--------E-21252BBH01-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE ALLOCATED PAGES
AX = 252Bh
BH = 01h
???
Return: ???
--------E-21252BBH02-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE PHYSICAL DEVICE PAGES
AX = 252Bh
BH = 02h
???
Return: ???
--------E-21252BBH03-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - MAP DATA FILE
AX = 252Bh
BH = 03h
???
Return: ???
SeeAlso: AX=252Bh/BL=0Bh
--------E-21252BBH04-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - GET PAGE TYPES
AX = 252Bh
BH = 04h
???
Return: ???
Note: returns one word per page
SeeAlso: #0529

Bitfields for Phar Lap page information:
Bit(s) Description (Table 0529)
7 mapped to read/write data file
6 mapped to read-only data file
5 swapped to disk
4 locked
3-0 page type
0 unmapped
1 allocated
2 physical device page
--------E-21252B-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - VIRTUAL MEMORY MANAGEMENT - PAGE LOCKING
AX = 252Bh
BH = function
05h lock pages
06h unlock pages
BL = address type
00h linear address
ECX = linear start address of memory region
01h segmented address
ES:ECX -> start of memory region
EDX = size of memory region in bytes
Return: CF clear if successful
CF set on error
Note: this function is also supported by FlashTek X-32VM; if X-32 is not
using virtual memory, this function always succeeds
--------E-21252B-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - FREE PHYSICAL PAGES
AX = 252Bh
BH = function (07h,08h)
???
Return: ???
--------E-21252BBH09-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1 - GET PAGETABLE ENTRY/PAGE TABLE INFO
AX = 252Bh
BH = 09h
BL = subfunction
00h get page table entry by linear address
ECX = linear address for which to get page table entry
01h get page table entry by logical address
ES:ECX = address for which to get page table entry
Return: CF clear if successful
EAX = page table entry
EBX = additional page table information
CF set on error
EAX = error code
0009h invalid address
0082h running under DPMI
SeeAlso: AX=251Dh,AX=252Bh/BH=0Ah

--------E-21252BBH0A-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1 - SET PAGETABLE ENTRY/PAGE TABLE INFO
AX = 252Bh
BH = 0Ah
BL = subfunction
00h set page table entry for linear address
ECX = linear address for which to get page table entry
01h set page table entry for logical address
ES:ECX = address for which to get page table entry
ESI = page table entry
EDI = additional page table information
Return: CF clear if successful
CF set on error
EAX = error code
0009h invalid address
0082h running under DPMI
SeeAlso: AX=252Bh/BH=09h
--------E-21252BBH0B-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1+ - MAP DATA FILE AT FILE OFFSET
AX = 252Bh
BH = 0Bh
BL = subfunction
00h by linear address
ECX = linear address at which to map data file
01h by logical address
ES:ECX = logical address at which to map data file
EDX = number of bytes to map
DS:ESI -> mapping structure (see #0530)
DS:EDI -> ASCIZ filename
Return: CF clear if successful
CF set on error
EAX = error code
0002h file error
ECX = phase (01h opening file, 02h seeking, 03h reading)
EDX = error code returned by DOS
0009h invalid address
0081h invalid parameters or 386|VMM not present
0086h all 386|VMM file handles already in use
SeeAlso: AX=252Bh/BH=03h,AX=252Bh/BH=09h

Format of Phar Lap mapping structure:
Offset Size Description (Table 0530)
00h DWORD starting file offset to be mapped
04h DWORD DOS file access and sharing modes (see #0559 at INT 21/AH=3Dh)
--------E-21252C-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - ADD UNMAPPED PAGES AT END OF SEGMENT
AX = 252Ch
BX = segment selector
ECX = number of 4K pages to add
Return: CF clear if successful
EAX = offset in segment of beginning of unmapped pages
CF set on error
EAX = error code
08h insufficent memory
09h invalid selector
82h not supported by current DPMI
--------E-21252D-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.3+ - CLOSE VMM FILE HANDLE
AX = 252Dh
EBX = VMM file handle
Return: CF clear if successful
CF set on error
EAX = error code (81h invalid VMM handle)
--------E-21252E-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.3+ - GET/SET VMM PARAMETERS
AX = 252Eh
CL = direction (00h get parameters, 01h set parameters)
DS:EBX -> parameter buffer (see #0531)
Return: CF clear if successful
CF set on error
EAX = error code (81h bad parameter value)

Format of Phar Lap VMM parameter buffer:
Offset Size Description (Table 0531)
00h DWORD flags
bit 0: page fault logging enabled
---v5.0+ ---
bit 1: swap extender to disk during DOS EXEC call
bit 2: don't zero allocated memory
04h DWORD scan period for page aging, in milliseconds
08h DWORD maximum size (in bytes) to check on each page scan
0Ch 52 BYTEs unused
--------E-21252F-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - WRITE RECORD TO VMM PAGE LOG FILE
AX = 252Fh
DS:EBX -> data to be written
CX = size of data in bytes
Return: CF clear if successful
CF set on error
EAX = error code (85h no page log file or not 386/VMM)
--------E-212530-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.3+ - SET SIZE OF BUFFER FOR DOS CALLS
AX = 2530h
ECX = size of data buffer in bytes (1024 to 65536)
Return: CF clear if successful
CF set on error
EAX = error code
08h insufficient low memory
81h invalid size
SeeAlso: AX=2517h
--------E-212531-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v3.0 - READ/WRITE LDT DESCRIPTOR
AX = 2531h
BX = segment selector
ECX = direction (00h read, 01h write)
DS:EDX -> 8-byte buffer for descriptor contents
Return: CF clear if successful
CF set on error
EAX = error code
81h invalid selector
82h DPMI running, or not a code or data segment
--------E-212532-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET EXCEPTION HANDLER VECTOR
AX = 2532h
CL = exception number (00h-0Fh)
Return: CF clear if successful
ES:EBX = CS:EIP of current exception handler
CF set on error (CL > 0Fh)
Notes: this call is also supported by the FlashTek X-32VM extender
this function is incompatible with 386|VMM; use AX=2522h instead
SeeAlso: AX=2522h,AX=2533h
--------E-212533-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET EXCEPTION HANDLER VECTOR
AX = 2533h
CL = exception number (00h-0Fh)
DS:EDX = CS:EIP of new exception handler
Return: CF clear if successful
CF set on error (CL > 0Fh)
Notes: this call is also supported by the FlashTek X-32VM extender
this function is incompatible with 386|VMM; use AX=2522h instead
SeeAlso: AX=2522h,AX=2532h
--------E-212534-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - GET INTERRUPT FLAG
AX = 2534h
Return: CF clear
EAX = interrupt state (00h disabled, 01h enabled)
--------E-212535-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - READ/WRITE SYSTEM REGISTERS
AX = 2535h
EBX = direction (00h read registers, 01h write)
DS:EDX -> system register record (see #0532)
Return: CF clear
Note: this call is only available under MS Windows if PHARLAP.386 VDD is
installed

Format of Phar Lap system register record:
Offset Size Description (Table 0532)
00h DWORD CR0
04h 4 DWORDs DR0,DR1,DR2,DR3
14h 2 DWORDs reserved
1Ch 2 DWORDs DR6,DR7
24h 3 DWORDs reserved
--------E-212536----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0+ - MIN/MAX EXTENDED/CONV MEMORY USAGE
AX = 2536h
EBX = bit flags
bit 0: modifying conventional memory rather than extended memory
bit 1: setting maximum memory usage rather than minimum
ECX = new limit in 4K pages
Return: CF clear if successful
EAX = new limit
CF set on error
EAX = error code (08h memory error or -NOPAGE set)
EBX = maximum limit in pages
ECX = minimum limit in pages
--------E-212537----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - ALLOCATE DOS MEMORY ABOVE DOS BUFFER
AX = 2537h
BX = number of paragraphs to allocate
Return: CF clear if successful
AX = real-mode segment of allocated block
CF set on error
AX = error code
07h MS-DOS memory chain corrupted
08h insufficient low memory
BX = size in paragraphs of largest free block
SeeAlso: AH=48h
--------E-212538----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - READ PROTMODE REGS AFTER SFTWARE INT
AX = 2538h
DS:EBX -> buffer for registers (see #0525)
ECX = register record to retrieve
00h first interrupt state
01h next interrupt state
EDX = handle for current interrupt state
Return: CF clear if successful
DS:EBX buffer filled
EDX = handle of current interrupt state
ESI = number of interrupt which occurred
CF set on error
EAX = error code
81h invalid handle in EDX
83h register saving not enabled
84h no more interrupt states
SeeAlso: AX=2527h,AX=2528h
--------E-212539----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - GET OFFSET OF .EXP FILE HEADER
AX = 2539h
BX = MS-DOS file handle for open file
Return: CF clear if successful
EAX = offset of .EXP header in file
CF set on error
EAX = error code (02h file error)
EBX = file error code
02h DOS error seeking
03h DOS error reading
04h invalid file type
05h invalid file format
ECX = DOS error code if EBX=02h or 03h
current file position in file modified
--------E-21253A----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - INSTALL MOD. SEG FAILURE HANDLER
AX = 253Ah
ES:EBX -> function to be called when INT 21/AH=4Ah is about to return
an error
Return: CF clear
ES:EBX -> previous handler
SeeAlso: AH=4Ah
--------E-21253B----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - JUMP TO REAL MODE CODE, NO CONTEXT
AX = 253Bh
DS:EBX -> buffer containing register contents (see #0525)
Return: never returns
SeeAlso: AX=2528h
--------E-21253C-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v3.0+ - SHRINK 386|VMM SWAP FILE
AX = 253Ch
Return: CF clear
EAX = old size of swap file in bytes
EBX = new size of swap file in bytes
--------E-21253D-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.0+ - READ/WRITE IDT DESCRIPTOR
AX = 253Dh
BL = interrupt number
ECX = direction (0 = read, 1 = write)
DS:EDX -> 8-byte buffer for descriptor
Return: CF clear if successful
DS:EDX filled if reading
CF set on error
EAX = error code (0082h if running under DPMI)
Desc: access hardware-level IDT rather than the internal 386/DOS-Extender
shadow IDT
Notes: this call will always fail under DPMI because it is not possible to
access the IDT
the descriptor is not checked when writing
this call can normally be used only by programs running in ring 0
because the processor does not allow an interrupt to be vectored to
a less privileged ring
--------E-21253F-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender v6.0+ - ALLOCATE LDT DESCRIPTOR
AX = 253Fh
BX = LDT descriptor to allocate (0000h for any)
???
Return: ???
--------E-212540-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender v6.0+ - FORCE ALIAS OF SEGMENT
AX = 2540h
???
Return: ???
--------E-212544-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender v6.0+ - FREE DLL
AX = 2544h
???
Return: ???
--------E-212545-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender v6.0+ - GET/SET PROCEDURE ADDRESS
AX = 2545h
ECX = direction (00h get, 01h set)
???
Return: ???
--------E-212546-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender v6.0+ - GET MODULE HANDLE
AX = 2546h
???
Return: ???
--------E-2125C0-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - ALLOCATE MS-DOS MEMORY BLOCK
AX = 25C0h
BX = number of 16-byte paragraphs of MS-DOS memory requested
Return: CF clear if successful
AX = real-mode paragraph address of memory
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C1h,AX=25C2h
--------E-2125C1-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - RELEASE MS-DOS MEMORY BLOCK
AX = 25C1h
CX = real-mode paragraph address of memory block to free
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
09h invalid memory block address in CX
SeeAlso: AX=25C0h,AX=25C2h
--------E-2125C2-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - MODIFY MS-DOS MEMORY BLOCK
AX = 25C2h
BX = new requested block size in paragraphs
CX = real-mode paragraph address of memory block to modify
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
09h invalid memory block address in CX
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C0h,AX=25C1h
--------E-2125C3-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - EXECUTE PROGRAM
AX = 25C3h
ES:EBX -> pointer to parameter block (see #0534)
DS:EDX -> pointer to ASCIZ program filename
Return: CF clear if successful
all registers unchanged
CF set on error
EAX = error code (see #0533)

(Table 0533)
Values for Phar Lap error code:
01h function code in AL is invalid ???
02h file not found or path invalid
05h access denied
08h insufficient memory to load program
0Ah environment invalid
0Bh invalid file format

Format of parameter block:
Offset Size Description (Table 0534)
00h DWORD 32-bit offset of environment string
04h WORD segment selector of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment selector of command-tail string
--------D-2126-------------------------------
INT 21 - DOS 1+ - CREATE NEW PROGRAM SEGMENT PREFIX
AH = 26h
DX = segment at which to create PSP (see #0535)
Notes: new PSP is updated with memory size information; INTs 22h, 23h, 24h
taken from interrupt vector table; the parent PSP field is set to 0
(DOS 2+) DOS assumes that the caller's CS is the segment of the PSP to
copy
SeeAlso: AH=4Bh,AH=50h,AH=51h,AH=55h,AH=62h,AH=67h

Format of Program Segment Prefix (PSP):
Offset Size Description (Table 0535)
00h 2 BYTEs INT 20 instruction for CP/M CALL 0 program termination
the CDh 20h here is often used as a signature for a valid PSP
02h WORD segment of first byte beyond memory allocated to program
04h BYTE (DOS) unused filler
(OS/2) count of fake DOS version returns
05h BYTE CP/M CALL 5 service request (FAR CALL to absolute 000C0h)
BUG: (DOS 2+) PSPs created by INT 21/AH=4Bh point at 000BEh
06h WORD CP/M compatibility--size of first segment for .COM files
08h 2 BYTEs remainder of FAR JMP at 05h
0Ah DWORD stored INT 22 termination address
0Eh DWORD stored INT 23 control-Break handler address
12h DWORD DOS 1.1+ stored INT 24 critical error handler address
16h WORD segment of parent PSP
18h 20 BYTEs DOS 2+ Job File Table, one byte per file handle, FFh = closed
2Ch WORD DOS 2+ segment of environment for process (see #0536)
2Eh DWORD DOS 2+ process's SS:SP on entry to last INT 21 call
32h WORD DOS 3+ number of entries in JFT (default 20)
34h DWORD DOS 3+ pointer to JFT (default PSP:0018h)
38h DWORD DOS 3+ pointer to previous PSP (default FFFFFFFFh in 3.x)
used by SHARE in DOS 3.3
3Ch BYTE DOS 4+ (DBCS) interim console flag (see AX=6301h)
3Dh BYTE (APPEND) TrueName flag (see INT 2F/AX=B711h)
3Eh BYTE (Novell NetWare) flag: next byte initialized if CEh
(OS/2) capabilities flag
3Fh BYTE (Novell NetWare) Novell task number if previous byte is CEh
40h 2 BYTEs DOS 5+ version to return on INT 21/AH=30h
42h WORD (MSWindows3) selector of next PSP (PDB) in linked list
Windows keeps a linked list of Windows programs only
44h WORD (MSWindows3) "PDB_Partition"
46h WORD (MSWindows3) "PDB_NextPDB"
48h BYTE (MSWindows3) bit 0 set if non-Windows application (WINOLDAP)
49h BYTE unused by DOS versions <= 6.00
4Ch WORD (MSWindows3) "PDB_EntryStack"
4Eh 2 BYTEs unused by DOS versions <= 6.00
50h 3 BYTEs DOS 2+ service request (INT 21/RETF instructions)
53h 2 BYTEs unused in DOS versions <= 6.00
55h 7 BYTEs unused in DOS versions <= 6.00; can be used to make first FCB
into an extended FCB
5Ch 16 BYTEs first default FCB, filled in from first commandline argument
overwrites second FCB if opened
6Ch 16 BYTEs second default FCB, filled in from second commandline argument
overwrites beginning of commandline if opened
7Ch 4 BYTEs unused
80h 128 BYTEs commandline / default DTA
command tail is BYTE for length of tail, N BYTEs for the tail,
followed by a BYTE containing 0Dh
Notes: in DOS v3+, the limit on simultaneously open files may be increased by
allocating memory for a new open file table, filling it with FFh,
copying the first 20 bytes from the default table, and adjusting the
pointer and count at 34h and 32h. However, DOS will only copy the
first 20 file handles into a child PSP (including the one created on
EXEC).
network redirectors based on the original MS-Net implementation use
values of 80h-FEh in the open file table to indicate remote files;
Novell NetWare also uses values from FEh down to 80h or one more than
FILES= (whichever is greater) to indicate remote files
MS-DOS 5.00 incorrectly fills the FCB fields when loading a program
high; the first FCB is empty and the second contains the first
parameter
some DOS extenders place protected-mode values in various PSP fields
such as the "parent" field, which can confuse PSP walkers. Always
check either for the CDh 20h signature or that the suspected PSP is
at the beginning of a memory block which owns itself (the preceding
paragraph should be a valid MCB with "owner" the same as the
suspected PSP).
Novell NetWare updates the fields at offsets 3Eh and 3Fh without
checking that a legal PSP segment is current; see AH=50h for further
discussion

Format of environment block:
Offset Size Description (Table 0536)
00h N BYTEs first environment variable, ASCIZ string of form "var=value"
N BYTEs second environment variable, ASCIZ string
...
N BYTEs last environment variable, ASCIZ string of form "var=value"
BYTE 00h
---DOS 3+---
WORD number of strings following environment (normally 1)
N BYTEs ASCIZ full pathname of program owning this environment
other strings may follow
--------D-2127-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK READ FROM FCB FILE
AH = 27h
CX = number of records to read
DS:DX -> opened FCB (see #0506)
Return: AL = status
00h successful, all records read
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial read
[DTA] = records read from file
CX = number of records read (return AL = 00h or 03h)
Notes: read begins at current file position as specified in FCB; the file
position is updated after reading
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=28h,AH=3Fh
--------D-2128-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK WRITE TO FCB FILE
AH = 28h
CX = number of records to write
DS:DX -> opened FCB (see #0506)
[DTA] = records to write
Return: AL = status
00h successful
01h disk full or file read-only
02h segment wrap in DTA
CX = number of records written
Notes: write begins at current file position as specified in FCB; the file
position is updated after writing
if CX = 0000h on entry, no data is written; instead the file size is
adjusted to be the same as the file position specified by the random
record and record size fields of the FCB
if the data to be written is less than a disk sector, it is copied into
a DOS disk buffer, to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=22h,AH=27h,AH=40h,AH=59h
--------D-2129-------------------------------
INT 21 - DOS 1+ - PARSE FILENAME INTO FCB
AH = 29h
AL = parsing options (see #0537)
DS:SI -> filename string (both '*' and '?' wildcards OK)
ES:DI -> buffer for unopened FCB
Return: AL = result code
00h successful parse, no wildcards encountered
01h successful parse, wildcards present
FFh failed (invalid drive specifier)
DS:SI -> first unparsed character
ES:DI buffer filled with unopened FCB (see #0506)
Notes: asterisks expanded to question marks in the FCB
all processing stops when a filename terminator is encountered
cannot be used with filespecs which include a path (DOS 2+)
Novell NetWare monitors the result code since an 'invalid drive' may
signal an attempt to reconnect a network drive; if there are no
connections to the specified drive, NetWare attempts to build a
connection and map the drive to the SYS:LOGIN directory
SeeAlso: AH=0Fh,AH=16h,AH=26h

Bitfields for parsing options:
Bit(s) Description (Table 0537)
0 skip leading separators
1 use existing drive number in FCB if no drive is specified, instead of
setting field to zero
2 use existing filename in FCB if no base name is specified, instead of
filling field with blanks
3 use existing extension in FCB if no extension is specified, instead of
filling field with blanks
4-7 reserved (0)
--------D-212A-------------------------------
INT 21 - DOS 1+ - GET SYSTEM DATE
AH = 2Ah
Return: CX = year (1980-2099)
DH = month
DL = day
---DOS 1.10+---
AL = day of week (00h=Sunday)
SeeAlso: AH=2Bh"DOS",AH=2Ch,AH=E7h,INT 1A/AH=04h,INT 2F/AX=120Dh
--------D-212B-------------------------------
INT 21 - DOS 1+ - SET SYSTEM DATE
AH = 2Bh
CX = year (1980-2099)
DH = month
DL = day
Return: AL = status
00h successful
FFh invalid date, system date unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Ah,AH=2Dh,INT 1A/AH=05h
--------E-212B--CX4149-----------------------
INT 21 - AI Architects - ??? - INSTALLATION CHECK
AH = 2Bh
CX = 4149h ('AI')
DX = 413Fh ('A?')
Return: AL <> FFh if installed
Note: Borland's TKERNEL makes this call
--------c-212B--CX4358-----------------------
INT 21 - Super PC-Kwik v3.20+ - INSTALLATION CHECK
AH = 2Bh
CX = 4358h ('CX')
Return: AL = FFh if PC-Kwik/PC-Cache not installed
AL = 00h if installed
CF clear
CX = 6378h ('cx')
BX = ???
DX = version (DH = major version, DL = binary minor version)
Note: PC Tools PC-Cache v5.x and Qualitas Qcache v4.00 are OEM versions of
Super PC-Kwik, and thus support this call (PC-Cache 5.1 corresponds
to PC-Kwik v3.20)
SeeAlso: INT 13/AH=A0h,INT 13/AH=B0h,INT 16/AX=FFA5h/CX=1111h
Index: PC-Cache;installation check|Qualitas Qcache;installation check
Index: installation check;PC-Cache 5.x|installation check;Qualitas Qcache
--------Q-212B--CX4445-----------------------
INT 21 - DESQview - INSTALLATION CHECK
AH = 2Bh
CX = 4445h ('DE')
DX = 5351h ('SQ')
AL = subfunction (DV v2.00+)
01h get version
Return: BX = version (BH = major, BL = minor)
Note: early copies of v2.00 return 0002h
02h get shadow buffer info, and start shadowing
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
04h get shadow buffer info
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
05h stop shadowing
Return: AL = FFh if DESQview not installed
Notes: in DESQview v1.x, there were no subfunctions; this call only identified
whether or not DESQview was loaded. DESQview v2.52 performs function
01h for all subfunction requests 0Ch and higher and appears to ignore
all lower-numbered functions not listed here.
DESQview versions 2.50-2.52 are part of DESQview/X v1.0x; version 2.53
is part of DESQview/X v1.10; and version 2.63 is part of DESQview/X
v2.00.
BUG: subfunction 05h does not appear to work correctly in DESQview 2.52
SeeAlso: INT 10/AH=FEh,INT 10/AH=FFh,INT 15/AX=1024h,INT 15/AX=DE30h
--------U-212B--CX454C-----------------------
INT 21 - ELRES v1.1 - INSTALLATION CHECK
AH = 2Bh
CX = 454Ch ('EL')
DX = 5253h ('RS')
Return: ES:BX -> ELRES history structure (see #0538)
DX = DABEh (signature, DAve BEnnett)
Program: ELRES is an MS-DOS return code (errorlevel) recorder by David H.
Bennett which stores recent errorlevel values, allows them to be
retrieved for use in batch files, and can place them in an
environment variable
SeeAlso: AH=4Bh"ELRES",AH=4Dh

Format of ELRES history structure:
Offset Size Description (Table 0538)
00h WORD number of return codes which can be stored by following buffer
02h WORD current position in buffer (treated as a ring)
04h N BYTEs ELRES buffer
--------m-212B01CX444D-----------------------
INT 21 - Quarterdeck DOS-UP.SYS v2.00 - INSTALLATION CHECK
AX = 2B01h
CX = 444Dh ('DM')
DX = 4158h ('AX')
Return: AX = 0000h if installed
BX = version??? (0002h)
CX = 4845h ('HE')
DX = 5245h ('RE')
ES = DOS-UP driver segment
--------T-212B01CX5441-----------------------
INT 21 - TAME v2.10+ - INSTALLATION CHECK
AX = 2B01h
CX = 5441h ('TA')
DX = 4D45h ('ME')
---v2.60---
BH = ???
00h skip ???, else do
Return: AL = 02h if installed
ES:DX -> data area in TAME-RES (see #0539,#0543,#0544)
Program: TAME is a shareware program by David G. Thomas which gives up CPU time
to other partitions under a multitasker when the current partition's
program incessantly polls the keyboard or system time

Format of TAME 2.10-2.20 data area:
Offset Size Description (Table 0539)
00h BYTE data structure minor version number (01h in TAME 2.20)
01h BYTE data structure major version number (07h in TAME 2.20)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD original INT 10h
16h DWORD original INT 14h
1Ah DWORD original INT 15h
1Eh DWORD original INT 16h
22h DWORD original INT 17h
26h DWORD original INT 21h
2Ah DWORD original INT 28h
2Eh WORD offset of TAME INT 10h handler
30h WORD offset of TAME INT 14h handler
32h WORD offset of TAME INT 15h handler
34h WORD offset of TAME INT 16h handler
36h WORD offset of TAME INT 17h handler
38h WORD offset of TAME INT 21h handler
3Ah WORD offset of TAME INT 28h handler
3Ch WORD X in /max:X,Y or /freq:X,Y
3Eh WORD Y in /max:X,Y or /freq:X,Y
40h WORD number of polls remaining before next task switch
42h WORD /KEYIDLE value
44h BYTE interrupts already grabbed by TAME (see #0540)
45h BYTE flags for interrupts which may be acted on (same bits as above)
46h BYTE TAME enabled (01h) or disabled (00h)
47h BYTE /TIMEPOLL (01h) or /NOTIMEPOLL (00h)
48h BYTE /NOTIMER (01h) or /TIMER (00h)
49h BYTE window or task number for this task
4Ah BYTE multitasker type (see #0541)
4Bh BYTE type of task switching selected
bit 0: DESQview???
bit 1: DoubleDOS???
bit 2: TopView???
bit 3: KeySwitch
bit 4: HLT instruction
4Ch BYTE ???
4Dh BYTE flags
bit 1: /FREQ instead of /MAX
4Eh BYTE /FG: value
4Fh BYTE task switches left until next FGONLY DESQview API call
50h BYTE ???

Bitfields for interrupts already grabbed by TAME:
Bit(s) Description (Table 0540)
0 INT 10h
1 INT 14h
2 INT 15h
3 INT 16h
4 INT 17h
5 INT 21h
6 INT 28h

(Table 0541)
Values for multitasker type:
01h DESQview
02h DoubleDOS
03h TopView
04h OmniView
05h VM/386

Bitfields for type of task switching selected:
Bit(s) Description (Table 0542)
0 DESQview
1 DoubleDOS
2 TopView
3 OmniView
4 KeySwitch
5 HLT instruction

Format of TAME 2.30 data area:
Offset Size Description (Table 0543)
00h BYTE data structure minor version number (02h in TAME 2.30)
01h BYTE data structure major version number (0Ah in TAME 2.30)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h DWORD original INT 10h
26h DWORD original INT 14h
2Ah DWORD original INT 15h
2Eh DWORD original INT 16h
32h DWORD original INT 17h
36h DWORD original INT 21h
3Ah DWORD original INT 28h
3Eh WORD offset of TAME INT 10h handler
40h WORD offset of TAME INT 14h handler
42h WORD offset of TAME INT 15h handler
44h WORD offset of TAME INT 16h handler
46h WORD offset of TAME INT 17h handler
48h WORD offset of TAME INT 21h handler
4Ah WORD offset of TAME INT 28h handler
4Ch WORD X in /max:X,Y or /freq:X,Y
4Eh WORD Y in /max:X,Y or /freq:X,Y
50h WORD number of polls remaining before next task switch
52h WORD /KEYIDLE value
54h WORD /FG: value
56h WORD task switches left until next FGONLY DESQview API call
58h WORD multitasker version
5Ah WORD virtual screen segment
5Ch BYTE interrupts already grabbed by TAME (see #0540)
5Dh BYTE flags for interrupts which may be acted on (same bits as above)
5Eh BYTE window or task number for this task
5Fh BYTE multitasker type (see #0541)
60h BYTE type of task switching selected (bit flags) (see #0542)
61h BYTE watch_DOS
62h BYTE bit flags
bit 0: TAME enabled
bit 1: /FREQ instead of /MAX (counts in 3Ch and 3Eh per tick)
bit 2: /TIMEPOLL
bit 3: /KEYPOLL
bit 4: inhibit timer
bit 5: enable status monitoring
63h BYTE old status
64h WORD signature DA34h

Format of TAME 2.60 data area:
Offset Size Description (Table 0544)
00h BYTE data structure minor version number (02h in TAME 2.60)
01h BYTE data structure major version number (0Bh in TAME 2.60)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h 4 BYTEs ???
26h DWORD original INT 10h
2Ah DWORD original INT 14h
2Eh DWORD original INT 15h
32h DWORD original INT 16h
36h DWORD original INT 17h
3Ah DWORD original INT 21h
3Eh DWORD original INT 28h
42h WORD offset of TAME INT 10h handler
44h WORD offset of TAME INT 14h handler
46h WORD offset of TAME INT 15h handler
48h WORD offset of TAME INT 16h handler
4Ah WORD offset of TAME INT 17h handler
4Ch WORD offset of TAME INT 21h handler
4Eh WORD offset of TAME INT 28h handler
50h WORD X in /max:X,Y or /freq:X,Y
52h WORD Y in /max:X,Y or /freq:X,Y
54h WORD number of polls remaining before next task switch
56h WORD /KEYIDLE value
58h 4 BYTEs ???
5Ch WORD X in /boost:X,Y
5Eh WORD Y in /boost:X,Y
60h WORD /FG: value
62h WORD task switches remaining until next FGONLY DESQview API call
64h WORD multitasker version ???
66h WORD virtual screen segment
68h BYTE interrupts already grabbed by TAME (see #0540)
69h BYTE flags for interrupts which may be acted on (same bits as above)
6Ah BYTE window or task number for this task
6Bh BYTE multitasker type (see #0541)
6Ch BYTE type of task switching selected (bit flags) (see #0542)
6Dh BYTE watch_DOS
6Eh BYTE bit flags
bit 0: TAME enabled
bit 1: /FREQ instead of /MAX (counts in 50h and 52h per tick)
bit 2: /TIMEPOLL
bit 3: /KEYPOLL
bit 4: inhibit timer
bit 5: enable status monitoring
6Fh BYTE old status
70h WORD signature DA34h
--------v-212B16CX0643-----------------------
INT 21 - VIRUS - "Maltese Amoeba" - INSTALLATION CHECK
AX = 2B16h
CX = 0643h
Return: AX = 1603h if installed
--------R-212B44BX4D41-----------------------
INT 21 - pcANYWHERE IV/LAN - INSTALLATION CHECK
AX = 2B44h ('D')
BX = 4D41h ('MA')
CX = 7063h ('pc')
DX = 4157h ('AW')
Return: AX = resident program
4F4Bh ('OK') if large host resident
6F6Bh ('ok') if small host resident
CX:DX -> API entry point (see #0545)
SeeAlso: INT 16/AH=79h

(Table 0545)
Call pcANYWHERE API entry point with:
AX = 0000h get pcANYWHERE IV version
DS:SI -> BYTE buffer for host type code
Return: AH = version number
AL = revision number
DS:DI buffer byte filled with
00h full-featured host
01h limited-feature LAN host
other API may not be supported
AX = 0001h initialize operation
DS:SI -> initialization request structure (see #0546)
Return: AX = function status (see #0549)
AX = 0002h get status
Return: AH = current operating mode (see init req structure below)
AL = current connection status (see #0548)
AX = 0003h suspend remote screen updates
Return: AX = function status (see #0549)
AX = 0004h resume screen updates
Return: AX = function status (see #0549)
AX = 0005h end current remote access session
DS:SI -> termination request structure (see #0547)
Return: AX = function status (see #0549)
AX = 0006h remove pcANYWHERE IV from memory
Return: AX = status (see #0549)
AX = 8000h read data from communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters read/available
AX < 0 on error
AX = 8001h write data to communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters written
AX < 0 on error
AX = 8002h get connection status
Return: AX = status
> 0000h if connection active
= 0000h if connection lost
< 0000h on error

Format of pcANYWHERE initialization request structure:
Offset Size Description (Table 0546)
00h BYTE operating mode
00h wait for a call
01h hot key activates
02h incoming call activates
03h initiate a call
01h 3 BYTEs user ID to append to config file names
04h WORD DS-relative pointer to path for config files
06h WORD DS-relative pointer to path for program files

Format of pcANYWHERE termination request structure:
Offset Size Description (Table 0547)
00h BYTE operating mode after termination
00h wait for a call
01h hot key activates
02h incoming call activates
80h use current mode
FFh remove from memory

Bitfields for current connection status:
Bit(s) Description (Table 0548)
0 a physical connection is active
1 remove screen updating is active
2 connection checking is active
3 hot key detection is active
4 background file transfer is active

(Table 0549)
Values for pcANYWHERE function status:
0000h function completed successfully
FFD1h unable to release interrupt vectors
FFD2h unable to release allocated memory
FFF2h unable to establish a connection when operating mode is
"Initiate a call"
FFF3h modem configuration is invalid (corrupt config)
FFF4h modem initialization failed (no modem response)
FFF5h the communications device could not be initialized
FFF6h the host operator aborted the function
FFF7h the communications driver type specified in the configuration file is
different than the one loaded when pcANYWHERE IV was started
FFF9h the configuration file is invalid
FFFAh the configuration file could not be found
FFFBh no session is active
FFFCh a remote access session is active
FFFDh the specified operating mode is invalid
----------212B--CX6269-----------------------
INT 21 - WDTSR.COM - INSTALLATION CHECK
AH = 2Bh
CX = 6269h ('bi')
DX = 742Dh ('t-')
Return: AL = FFh if not installed
AL = 77h ('w') if WDTSR is installed
CX = 6174h ('at')
DX = 6368h ('ch')
ES = resident code segment
ES:DI -> identification and configuration data
Program: WDTSR is a driver for the bitWatch watchdog hardware by bit-design
GmbH
SeeAlso: AH=2Bh/CX=6269h"bitFOSSI",INT 14/AH=14h"FOSSIL",INT 15/AH=C3h
--------S-212B--CX6269-----------------------
INT 21 - bitFOSS - INSTALLATION CHECK
AH = 2Bh
CX = 6269h ('bi')
DX = 7446h ('tF')
Return: AL = FFh if not installed
AL = 4Fh ('O') if bitFOSS is installed
CX = 5353h ('SS')
DX = 494Ch ('IL')
ES = resident code segment
ES:DI -> identification data
Program: bitFOSS is a revision 5 FOSSIL driver
SeeAlso: AH=2Bh/CX=6269h"bitFOSSI",INT 11/AH=BCh
--------S-212B--CX6269-----------------------
INT 21 - bitFOSSI - INSTALLATION CHECK
AH = 2Bh
CX = 6269h ('bi')
DX = 7449h ('tI')
Return: AL = FFh if not installed
AL = 53h ('S') if bitFOSSI is installed
CX = 444Eh ('DN')
DX = 2D46h ('-F')
ES = resident code segment
ES:DI -> identification data
Program: bitFOSSI is a revision 5 FOSSIL driver for ???'s ISDN board
SeeAlso: AH=2Bh/CX=6269h/DX=7446h,INT 11/AH=BCh
--------D-212C-------------------------------
INT 21 - DOS 1+ - GET SYSTEM TIME
AH = 2Ch
Return: CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Note: on most systems, the resolution of the system clock is about 5/100sec,
so returned times generally do not increment by 1
on some systems, DL may always return 00h
SeeAlso: AH=2Ah,AH=2Dh,AH=E7h,INT 1A/AH=00h,INT 1A/AH=02h,INT 1A/AH=FEh
SeeAlso: INT 2F/AX=120Dh
--------v-212C00CX534B-----------------------
INT 21 - SKUDO - INSTALLATION CHECK
AX = 2C00h
CX = 534Bh ('SK')
DX = 5544h ('UD')
BX = 4F21h ('O!')
Return: AX = 5349h ('SI') if installed
CH = version number
CL = subversion
Program: SKUDO is an antivirus TSR by Jordi Mas
--------D-212D-------------------------------
INT 21 - DOS 1+ - SET SYSTEM TIME
AH = 2Dh
CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Return: AL = result
00h successful
FFh invalid time, system time unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Bh"DOS",AH=2Ch,INT 1A/AH=01h,INT 1A/AH=03h,INT 1A/AH=FFh"AT&T"
--------T-212D01CX7820-----------------------
INT 21 - PC-Mix - INSTALLATION CHECK
AX = 2D01h
CX = 7820h ('X ')
DX = 6D69h ('MI')
Return: AL = 00h if installed
--------D-212E--DL00-------------------------
INT 21 - DOS 1+ - SET VERIFY FLAG
AH = 2Eh
DL = 00h (DOS 1.x/2.x only)
AL = new state of verify flag
00h off
01h on
Notes: default state at system boot is OFF
when ON, all disk writes are verified provided the device driver
supports read-after-write verification
SeeAlso: AH=54h
--------D-212F-------------------------------
INT 21 - DOS 2+ - GET DISK TRANSFER AREA ADDRESS
AH = 2Fh
Return: ES:BX -> current DTA
Note: under the FlashTek X-32 DOS extender, the pointer is in ES:EBX
SeeAlso: AH=1Ah
--------D-2130-------------------------------
INT 21 - DOS 2+ - GET DOS VERSION
AH = 30h
---DOS 5+ ---
AL = what to return in BH
00h OEM number (as for DOS 2.0-4.0x)
01h version flag
Return: AL = major version number (00h if DOS 1.x)
AH = minor version number
BL:CX = 24-bit user serial number (most versions do not use this)
---if DOS <5 or AL=00h---
BH = MS-DOS OEM number (see #0550)

---if DOS 5+ and AL=01h---
BH = version flag
bit 3: DOS is in ROM
other: reserved (0)
Notes: the OS/2 v1.x Compatibility Box returns major version 0Ah (10)
the OS/2 v2.x Compatibility Box returns major version 14h (20)
the Windows/NT DOS box returns version 5.00, subject to SETVER
DOS 4.01 and 4.02 identify themselves as version 4.00; use
INT 21/AH=87h to distinguish between the original European MS-DOS 4.0
and the later PC-DOS 4.0x and MS-DOS 4.0x
IBM DOS 6.1 reports its version as 6.00; use the OEM number to
distinguish between MS-DOS 6.00 and IBM DOS 6.1 (there was never an
IBM DOS 6.0)
MS-DOS 6.21 reports its version as 6.20; version 6.22 returns the
correct value
the "Chicago" beta returns version 7.00 (reported in
_Microsoft_Systems_Journal_, August 1994).
DR-DOS 5.0 and 6.0 report version 3.31; Novell DOS 7 reports v6.00.
generic MS-DOS 3.30, Compaq MS-DOS 3.31, and others identify themselves
as PC-DOS by returning OEM number 00h
the version returned under DOS 4.0x may be modified by entries in
the special program list (see #0800 at AH=52h); the version returned
under DOS 5+ may be modified by SETVER--use AX=3306h to get the true
version number
SeeAlso: AX=3000h/BX=3000h,AX=3306h,AX=4452h,AH=87h,INT 15/AX=4900h
SeeAlso: INT 2F/AX=122Fh,INT 2F/AX=4010h,INT 2F/AX=E002h

(Table 0550)
Values for DOS OEM number:
00h IBM
01h Compaq
02h MS Packaged Product
04h AT&T
05h Zenith
06h Hewlett-Packard
0Dh Packard-Bell
16h DEC
23h Olivetti
29h Toshiba
33h Novell (Windows/386 device IDs only)
34h MS Multimedia Systems (Windows/386 device IDs only)
35h MS Multimedia Systems (Windows/386 device IDs only)
4Dh Hewlett-Packard
66h PhysTechSoft (PTS-DOS)
99h General Software's Embedded DOS
EEh DR-DOS
EFh Novell DOS
FFh Microsoft, Phoenix
--------E-2130-------------------------------
INT 21 - Phar Lap 386/DOS-Extender, Intel Code Builder - INSTALLATION CHECK
AH = 30h
EAX = 00003000h
EBX = 50484152h ("PHAR")
Return: AL = major DOS version
AH = minor DOS version
EAX bits 31-16 = 4458h ('DX') if 386/DOS-extender installed
BL = ASCII major version number
EAX bits 31-16 = 4243h ('BC') if Intel Code Builder installed
EDX = address of GDA
SeeAlso: AX=2501h,AX=FF00h,INT 2F/AX=F100h
--------v-2130--DXABCD-----------------------
INT 21 - VIRUS - "Possessed" - INSTALLATION CHECK
AH = 30h
DX = ABCDh
Return: DX = DCBAh if installed
SeeAlso: AX=0D20h,AX=30F1h
--------T-213000BX1234-----------------------
INT 21 - CTask 2.0+ - INSTALLATION CHECK
AX = 3000h
BX = 1234h
DS:DX -> 8-byte version string (DX < FFF0h) "CTask21",00h for v2.1-2.2
Return: AL = DOS major version
AH = DOS minor version
CX:BX -> Ctask global data block
Program: CTask is a multitasking kernel for C written by Thomas Wagner
Note: if first eight bytes of returned data block equal eight bytes passed
in, CTask is resident
--------O-213000BX3000-----------------------
INT 21 - PC-MOS/386 v3.0 - INSTALLATION CHECK/GET VERSION
AX = 3000h
BX = 3000h
CX = DX = 3000h
Return: AX = PC-MOS version
Program: PC-MOS/386 is a multitasking/multiuser MS-DOS-compatible operating
system by The Software Link, Inc.
SeeAlso: AH=30h,INT 38/AH=02h,INT 38/AH=10h
--------G-213022-----------------------------
INT 21 - StopPrg v2.0 - INSTALLATION CHECK
AX = 3022h
Return: AX = DOS version (see AH=30h)
CX = 1112h if StopPrg installed
BX = segment of resident code
Program: StopPrg is a resident program aborter by MAK-TRAXON's Prophet
Note: StopPrg may be temporarily disabled by storing 9090h in the word at
0000h:04FEh
--------v-2130F1-----------------------------
INT 21 - VIRUS - "Dutch-555"/"Quit 1992" - INSTALLATION CHECK
AX = 30F1h
Return: AL = 00h if resident
SeeAlso: AH=30h/DX=ABCDh,AX=330Fh
----------2130FFCX4445-----------------------
INT 21 - DESQ??? - INSTALLATION CHECK
AX = 30FFh
CX = 4445h ("DE")
DX = 5351h ("SQ")
Return: BH = 05h if installed
???
Note: called by DUBLDISK.COM v2.6; this function is not supported by
DESQview, so it may be for DESQview's precursor DESQ.
SeeAlso: AX=4404h"DUBLDISK"
--------D-2131-------------------------------
INT 21 - DOS 2+ - TERMINATE AND STAY RESIDENT
AH = 31h
AL = return code
DX = number of paragraphs to keep resident
Return: never
Notes: the value in DX only affects the memory block containing the PSP;
additional memory allocated via AH=48h is not affected
the minimum number of paragraphs which will remain resident is 11h
for DOS 2.x and 06h for DOS 3+
most TSRs can save some memory by releasing their environment block
before terminating (see #0535 at AH=26h,AH=49h)
SeeAlso: AH=00h,AH=4Ch,AH=4Dh,INT 20,INT 22,INT 27
--------D-2132-------------------------------
INT 21 - DOS 2+ - GET DOS DRIVE PARAMETER BLOCK FOR SPECIFIC DRIVE
AH = 32h
DL = drive number (00h = default, 01h = A:, etc)
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) (see #0551) for specified
drive
FFh invalid or network drive
Notes: the OS/2 compatibility box supports the DOS 3.3 version of this call
except for the DWORD at offset 12h
this call updates the DPB by reading the disk; the DPB may be accessed
via the DOS list of lists (see #0765 at AH=52h) if disk access is not
desirable.
undocumented prior to the release of DOS 5.0; only the DOS 4+ version
of the DPB has been documented, however
supported by DR-DOS 3.41+; DR-DOS 3.41-6.0 return the same data as
MS-DOS 3.31
SeeAlso: AH=1Fh,AH=52h

Format of DOS Drive Parameter Block:
Offset Size Description (Table 0551)
00h BYTE drive number (00h = A:, 01h = B:, etc)
01h BYTE unit number within device driver
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD number of reserved sectors at beginning of drive
08h BYTE number of FATs
09h WORD number of root directory entries
0Bh WORD number of first sector containing user data
0Dh WORD highest cluster number (number of data clusters + 1)
16-bit FAT if greater than 0FF6h, else 12-bit FAT
0Fh BYTE number of sectors per FAT
10h WORD sector number of first directory sector
12h DWORD address of device driver header
16h BYTE media ID byte
17h BYTE 00h if disk accessed, FFh if not
18h DWORD pointer to next DPB
---DOS 2.x---
1Ch WORD cluster containing start of current directory, 0000h=root,
FFFFh = unknown
1Eh 64 BYTEs ASCIZ pathname of current directory for drive
---DOS 3.x---
1Ch WORD cluster at which to start search for free space when writing
1Eh WORD number of free clusters on drive, FFFFh = unknown
---DOS 4.0-6.0---
0Fh WORD number of sectors per FAT
11h WORD sector number of first directory sector
13h DWORD address of device driver header
17h BYTE media ID byte
18h BYTE 00h if disk accessed, FFh if not
19h DWORD pointer to next DPB
1Dh WORD cluster at which to start search for free space when writing,
usually the last cluster allocated
1Fh WORD number of free clusters on drive, FFFFh = unknown
SeeAlso: #0801
--------D-2133-------------------------------
INT 21 - DOS 2+ - EXTENDED BREAK CHECKING
AH = 33h
AL = subfunction
00h get current extended break state
Return: DL = current state, 00h = off, 01h = on
01h set state of extended ^C/^Break checking
DL = new state
00h off, check only on character I/O functions
01h on, check on all DOS functions
Return: (Novell DOS 7) DL = old state of extended Break checks
Note: under DOS 3.1+ and DR-DOS, this function does not use any of the
DOS-internal stacks and may thus be called at any time
SeeAlso: AX=3302h
--------D-213302-----------------------------
INT 21 - DOS 3.x+ internal - GET AND SET EXTENDED CONTROL-BREAK CHECKING STATE
AX = 3302h
DL = new state (00h for OFF, 01h for ON)
Return: DL = old state of extended BREAK checking
Notes: this function does not use any of the DOS-internal stacks and may thus
be called at any time; one possible use is modifying Control-Break
checking from within an interrupt handler or TSR
not supported by DR-DOS through version 6.0; newly-supported by
Novell DOS 7
SeeAlso: AH=33h
--------D-213303-----------------------------
INT 21 - DOS 4+ - UNUSED
AX = 3303h
Return: nothing
Note: this function and AX=3304h were apparently intended to support a
code-page switching flag for OS/2 compatibility (OS/2 allows a file
to have a code page as an attribute); however, this function has
always been a NOP in public releases of DOS. See _DOS_Internals_
Chapter 2 for more information
SeeAlso: AX=3304h
--------D-213304-----------------------------
INT 21 - DOS 4+ - UNUSED
AX = 3304h
Return: nothing
Note: this function and AX=3303h were apparently intended to support a
code-page switching flag for OS/2 compatibility (OS/2 allows a file
to have a code page as an attribute); however, this function has
always been a NOP in public releases of DOS. See _DOS_Internals_
Chapter 2 for more information
SeeAlso: AX=3303h
--------D-213305-----------------------------
INT 21 - DOS 4+ - GET BOOT DRIVE
AX = 3305h
Return: DL = boot drive (1=A:,...)
Notes: fully reentrant
NEC 9800-series PCs always call the boot drive A: and assign the other
drive letters sequentially to the other drives in the system
--------D-213306-----------------------------
INT 21 - DOS 5+ - GET TRUE VERSION NUMBER
AX = 3306h
Return: BL = major version
BH = minor version
DL = revision (bits 2-0, all others 0)
DH = version flags
bit 3: DOS is in ROM
bit 4: DOS is in HMA
AL = FFh if true DOS version < 5.0
Notes: this function always returns the true version number, unlike AH=30h,
whose return value may be changed with SETVER
because of the conflict from the CBIS PowerLAN redirector (see next
entry), programs should check whether BH is less than 100 (64h)
and BL is at least 5 before accepting the returned BX as the true
version number; however, even this is not entirely reliable when
that redirector is loaded
fully reentrant
OS/2 v2.1 will return BX=0A14h (version 20.10)
the Windows NT DOS box returns BX=3205h (version 5.50)
Novell DOS 7 returns version 6.00
BUG: DR-DOS 5.0 and 6.0 return CF set/AX=0001h for INT 21/AH=33h
subfunctions other than 00h-02h and 05h, while MS-DOS returns AL=FFh
for invalid subfunctions
SeeAlso: AH=30h,INT 2F/AX=122Fh
--------N-213306-----------------------------
INT 21 - CBIS POWERLAN - NETWORK REDIRECTOR - ???
AX = 3306h
Return: AX = 3306h
BL = ??? (usually 00h)
BH = ??? (usually 00h or FFh)
Note: unknown function, is in conflict with DOS 5+ version call
SeeAlso: AX=3306h"DOS"
--------v-21330F-----------------------------
INT 21 - VIRUS - "Burghofer" - INSTALLATION CHECK
AX = 330Fh
Return: AL = 0Fh if resident (DOS returns AL=FFh)
SeeAlso: AX=30F1h,AX=33E0h
--------k-213341-----------------------------
INT 21 - Diet Disk v1.0 - INSTALLATION CHECK
AX = 3341h
Return: DX = 1234h if installed
CX = resident code segment
Program: Diet Disk is a public domain transparent data file compressor by
Barry Nance
--------v-2133E0-----------------------------
INT 21 - VIRUS - "Oropax" - INSTALLATION CHECK
AX = 33E0h
Return: AL = E0h if resident (DOS returns AL=FFh)
SeeAlso: AX=330Fh,AX=357Fh
--------D-2134-------------------------------
INT 21 - DOS 2+ - GET ADDRESS OF INDOS FLAG
AH = 34h
Return: ES:BX -> one-byte InDOS flag
Notes: this function executes on the DOS stack, and thus cannot be called
while another DOS function is already executing; you should use
this function once at the beginning of the program and store the
returned pointer rather than calling it when requiring DOS access
the value of InDOS is incremented whenever an INT 21 function begins
and decremented whenever one completes
during an INT 28 call, it is safe to call some INT 21 functions even
though InDOS may be 01h instead of zero
InDOS alone is not sufficient for determining when it is safe to
enter DOS, as the critical error handling decrements InDOS and
increments the critical error flag for the duration of the critical
error. Thus, it is possible for InDOS to be zero even if DOS is
busy.
SMARTDRV 4.0 sets the InDOS flag while flushing its buffers to disk,
then zeros it on completion
the critical error flag is the byte immediately following InDOS in
DOS 2.x, and the byte BEFORE the InDOS flag in DOS 3+ and
DR-DOS 3.41+ (except COMPAQ DOS 3.0, where the critical error flag
is located 1AAh bytes BEFORE the critical section flag)
for DOS 3.1+, an undocumented call exists to get the address of the
critical error flag (see AX=5D06h)
this function was undocumented prior to the release of DOS 5.0.
SeeAlso: AX=5D06h,AX=5D0Bh,INT 15/AX=DE1Fh,INT 28
--------D-2135-------------------------------
INT 21 - DOS 2+ - GET INTERRUPT VECTOR
AH = 35h
AL = interrupt number
Return: ES:BX -> current interrupt handler
Note: under DR-DOS 5.0+, this function does not use any of the DOS-internal
stacks and may thus be called at any time
SeeAlso: AH=25h,AX=2503h
--------E-213501-----------------------------
INT 21 P - FlashTek X-32VM - ALLOCATE PROTECTED-MODE SELECTOR
AX = 3501h
Return: CF clear if successful
BX = new selector
CF set on error (no more selectors available)
Note: the new selector will be an expand-up read/write data selector with
undefined base and limit
SeeAlso: AX=3502h,INT 31/AX=0000h
--------E-213502-----------------------------
INT 21 P - FlashTek X-32VM - DEALLOCATE PROTECTED-MODE SELECTOR
AX = 3502h
BX = selector
Return: CF clear if successful
CF set on error (invalid selector)
Note: only selectors allocated via AX=3501h should be deallocated
SeeAlso: AX=3501h,INT 31/AX=0001h
--------E-213503-----------------------------
INT 21 P - FlashTek X-32VM - SET SELECTOR BASE ADDRESS
AX = 3503h
BX = selector
ECX = base address
Return: CF clear if successful
CF set on error (invalid selector)
SeeAlso: AX=3504h,AX=3505h,INT 31/AX=0007h
--------E-213504-----------------------------
INT 21 P - FlashTek X-32VM - GET SELECTOR BASE ADDRESS
AX = 3504h
BX = selector
Return: CF clear if successful
ECX = absolute base address of selector
CF set on error (invalid selector)
SeeAlso: AX=3503h,INT 31/AX=0006h
--------E-213505-----------------------------
INT 21 P - FlashTek X-32VM - SET SELECTOR LIMIT
AX = 3505h
BX = selector
ECX = desired limit
Return: CF clear if successful
ECX = actual limit set
CF set on error (no more selectors available)
Note: the limit will be rounded down to nearest 4K boundary if the requested
limit is greater than 1MB
SeeAlso: AX=3503h,INT 31/AX=0008h
--------E-21350A-----------------------------
INT 21 P - FlashTek X-32VM - PHYSICAL ADDRESS MAPPING
AX = 350Ah
EBX = absolute physical address
ECX = size in bytes of area to map
Return: CF clear if successful
CF set on error (insufficient memory or service refused by DPMI host)
Notes: should not make repeated calls for the same physical address
there is no provision for unmapping memory
--------E-21350B-----------------------------
INT 21 P - FlashTek X-32VM - UPDATE AND RETURN AVAILABLE FREE MEMORY
AX = 350Bh
DS = default selector for DS
Return: CF clear
EAX = maximum amount of memory which can be allocated via AX=350Ch
SeeAlso: AX=350Ch
--------E-21350C-----------------------------
INT 21 P - FlashTek X-32VM - ALLOCATE A BLOCK OF MEMORY
AX = 350Ch
ECX = size of block in bytes
DS = default DS
Return: CF clear if successful
EAX = near pointer to new block
EDX = new lowest legal value for stack
CF set on error (requested size not multiple of 4K)
SeeAlso: AX=350Bh,AX=350Dh
--------E-21350D-----------------------------
INT 21 P - FlashTek X-32VM - RESERVE BLOCK OF MEMORY FOR 32-BIT STACK
AX = 350Dh
EBX = current ESP value
ECX = size of block in bytes
DS = default DS
Return: CF clear if successful
EBX = new value for ESP
EDX = suggested new limit for SS
CF set on error
Note: this function should only be called once during initialization
SeeAlso: AX=350Bh,AX=350Ch
--------v-21357F-----------------------------
INT 21 - VIRUS - "Agiplan"/"Month 4-6" - INSTALLATION CHECK
AX = 357Fh
Return: DX = FFFFh if installed
SeeAlso: AX=33E0h,AX=3DFFh
--------D-2136-------------------------------
INT 21 - DOS 2+ - GET FREE DISK SPACE
AH = 36h
DL = drive number (00h = default, 01h = A:, etc)
Return: AX = FFFFh if invalid drive
else
AX = sectors per cluster
BX = number of free clusters
CX = bytes per sector
DX = total clusters on drive
Notes: free space on drive in bytes is AX * BX * CX
total space on drive in bytes is AX * CX * DX
"lost clusters" are considered to be in use
according to Dave Williams' MS-DOS reference, the value in DX is
incorrect for non-default drives after ASSIGN is run
SeeAlso: AH=1Bh,AH=1Ch
--------D-213700-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - GET SWITCH CHARACTER
AX = 3700h
Return: AL = status
00h successful
DL = current switch character
FFh unsupported subfunction
Desc: Determine the character which is used to introduce command switches.
This setting is ignored by DOS commands in version 4.0 and higher,
but is honored by many third-party programs.
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
always returns AL=00h/DL=2Fh for MS-DOS 5+ and DR-DOS 3.41+
SeeAlso: AX=3701h
--------D-213701-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER
AX = 3701h
DL = new switch character
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
ignored by MS-DOS 5+ and DR-DOS 3.41+; DR-DOS 6.0 leaves AX unchanged
SeeAlso: AX=3700h
--------D-2137-------------------------------
INT 21 - DOS 2.x and 3.3+ only - "AVAILDEV" - SPECIFY \DEV\ PREFIX USE
AH = 37h
AL = subfunction
02h get availdev flag
Return: DL = 00h \DEV\ must precede character device names
= nonzero \DEV\ is optional
03h set availdev flag
DL = 00h \DEV\ is mandatory
= nonzero \DEV\ is optional
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: all versions of DOS from 2.00 allow \DEV\ to be prepended to device
names without generating an error even if the directory \DEV does
not actually exist (other paths generate an error if they do not
exist).
although MS-DOS 3.3+ and DR-DOS 3.41+ accept these calls, they have no
effect, and AL=02h always returns DL=FFh
--------k-2137D0BX899D-----------------------
INT 21 - DIET v1.43e - TSR INSTALLATION CHECK
AX = 37D0h
BX = 899Dh ('DI' + 'ET')
Return: AL = FFh if not present as TSR (default return value from DOS)
AX = 0000h if installed as a TSR
CX = 899Dh
DX = version ID
Program: DIET is a transparent file copressor/decompressor by Teddy Matsumoto
SeeAlso: AX=37D1h,AX=37D2h,AX=37D4h,AX=37D6h,AX=37DFh,AX=4BF0h,AX=4BF1h
--------k-2137D1BX899D-----------------------
INT 21 - DIET v1.43e - GET DIET.EXE RESIDENT SEGMENT
AX = 37D1h
BX = 899Dh ('DI' + 'ET')
Return: AX = 0000h
CX = code segment of TSR part of DIET.EXE
DX = memory block segment of TSR DIET.EXE
(0000h if installed as device driver)
SeeAlso: AX=37D0h,AX=37DFh
--------k-2137D2BX899D-----------------------
INT 21 - DIET v1.43e - GET TSR CONTROL FLAGS
AX = 37D2h
BX = 899Dh ('DI' + 'ET')
Return: AX = 0000h
DL = control flag (00h active, else disabled)
DH = skip flag (nonzero while TSR active)
SeeAlso: AX=37D0h,AX=37D3h,AX=37D4h
--------k-2137D3BX899D-----------------------
INT 21 - DIET v1.43e - SET TSR CONTROL FLAGS
AX = 37D3h
BX = 899Dh ('DI' + 'ET')
DL = control flag (00h active, else disabled)
DH = skip flag (00h)
Return: AX = 0000h
SeeAlso: AX=37D0h,AX=37D2h,AX=37D5h
--------k-2137D4BX899D-----------------------
INT 21 - DIET v1.43e - GET TSR OPTIONS
AX = 37D4h
BX = 899Dh ('DI' + 'ET')
Return: AX = 0000h
DX = TSR options (see #0552)
SeeAlso: AX=37D0h,AX=37D2h,AX=37D5h

Bitfields for DIET TSR options:
Bit(s) Description (Table 0552)
0 automated compression of DIETed file
1 automated compression of newly-created file
2 suppress DIET message
3 display original file size
4-15 reserved (0)
--------k-2137D5BX899D-----------------------
INT 21 - DIET v1.43e - SET TSR OPTIONS
AX = 37D5h
BX = 899Dh ('DI' + 'ET')
DX = TSR options (see #0552)
Return: AX = 0000h
Program: DIET is a transparent file copressor/decompressor by Teddy Matsumoto
SeeAlso: AX=37D0h,AX=37D3h,AX=37D4h
--------k-2137D6BX899D-----------------------
INT 21 - DIET v1.43e - GET TEMPORARY DIRECTORY NAMES
AX = 37D6h
BX = 899Dh ('DI' + 'ET')
Return: AX = 0000h
DS:DX -> name of temporary directory or 0000h:0000h for current dir
SeeAlso: AX=37D0h,AX=37D7h
--------k-2137D7BX899D-----------------------
INT 21 - DIET v1.43e - SET TEMPORARY DIRECTORY NAMES
AX = 37D7h
BX = 899Dh ('DI' + 'ET')
DS:DX -> ASCIZ name of temporary directory (max 61 chars)
0000h:0000h for current directory
Return: AX = 0000h
Note: the specified directory name must include a drive letter and end with
a backslash
SeeAlso: AX=37D0h,AX=37D6h
--------k-2137DCBX899D-----------------------
INT 21 - DIET v1.43e - SET ADDRESS OF EXTERNAL PROCEDURE
AX = 37DCh
BX = 899Dh ('DI' + 'ET')
DS:DX -> external procedure
Return: AX = 0000h
Note: the resident code will call the specified external procedure at the
beginning of decompression and when compression is exited on failure
SeeAlso: AX=37DDh

(Table 0553)
Values DIET external procedure is called with:
STACK: WORD class
FFFDh creation failed for unknown reasons
FFFEh creation failed due to lack of space
FFFFh file creation error
else file handle of DIETed file to be decompressed
DWORD -> compressed filename
DWORD -> decompressed or temporary filename
Return: SI,DI,BP,DS,ES must be preserved by external procedure
--------k-2137DDBX899D-----------------------
INT 21 - DIET v1.43e - RELEASE EXTERNAL PROCEDURE
AX = 37DDh
BX = 899Dh ('DI' + 'ET')
Program: DIET is a transparent file copressor/decompressor by Teddy Matsumoto
Note: unlinks the external procedure specified by AX=37DCh
SeeAlso: AX=37DCh
--------k-2137DEBX899D-----------------------
INT 21 - DIET v1.43e - READ EMS STATUS
AX = 37DEh
BX = 899Dh ('DI' + 'ET')
Return: AX = 0000h
CX = EMS status
0000h not used
0001h used as work area
0002h used for code and as work area
DX = EMM handle when EMS is in use
--------k-2137DFBX899D-----------------------
INT 21 - DIET v1.43e - UNLOAD TSR
AX = 37DFh
BX = 899Dh ('DI' + 'ET')
Return: AX = status
0000h successful
00FFh failed
Program: DIET is a transparent file copressor/decompressor by Teddy Matsumoto
SeeAlso: AX=37D0h
Index: uninstall;DIET
--------D-2138-------------------------------
INT 21 - DOS 2+ - GET COUNTRY-SPECIFIC INFORMATION
AH = 38h
--DOS 2.x--
AL = 00h get current-country info
DS:DX -> buffer for returned info (see #0554,#0555)
Return: CF set on error
AX = error code (02h)
CF clear if successful
AX = country code (MS-DOS 2.11 only)
buffer at DS:DX filled
--DOS 3+--
AL = 00h for current country
AL = 01h thru 0FEh for specific country with code <255
AL = 0FFh for specific country with code >= 255
BX = 16-bit country code
DS:DX -> buffer for returned info (see #0555)
Return: CF set on error
AX = error code (02h)
CF clear if successful
BX = country code
DS:DX buffer filled
Note: this function is not supported by the Borland DPMI host, but no error
is returned; as a workaround, one should allocate a buffer in
conventional memory with INT 31/AX=0100h and simulate an INT 21 with
INT 31/AX=0300h
SeeAlso: AH=65h,INT 10/AX=5001h,INT 2F/AX=110Ch,INT 2F/AX=1404h

Format of DOS 2.00-2.10 country info:
Offset Size Description (Table 0554)
00h WORD date format 0 = USA mm dd yy
1 = Europe dd mm yy
2 = Japan yy mm dd
02h BYTE currency symbol
03h BYTE 00h
04h BYTE thousands separator char
05h BYTE 00h
06h BYTE decimal separator char
07h BYTE 00h
08h 24 BYTEs reserved

Format of DOS 2.11+ country info:
Offset Size Description (Table 0555)
00h WORD date format (see #0554)
02h 5 BYTEs ASCIZ currency symbol string
07h 2 BYTEs ASCIZ thousands separator
09h 2 BYTEs ASCIZ decimal separator
0Bh 2 BYTEs ASCIZ date separator
0Dh 2 BYTEs ASCIZ time separator
0Fh BYTE currency format
bit 2 = set if currency symbol replaces decimal point
bit 1 = number of spaces between value and currency symbol
bit 0 = 0 if currency symbol precedes value
1 if currency symbol follows value
10h BYTE number of digits after decimal in currency
11h BYTE time format
bit 0 = 0 if 12-hour clock
1 if 24-hour clock
12h DWORD address of case map routine
(FAR CALL, AL = character to map to upper case [>= 80h])
16h 2 BYTEs ASCIZ data-list separator
18h 10 BYTEs reserved

(Table 0556)
Values for country code:
001h United States
002h Canadian-French
003h Latin America
01Fh Netherlands
020h Belgium
021h France
022h Spain
024h Hungary (not supported by DR-DOS 5.0)
026h Yugoslavia (not supported by DR-DOS 5.0)
027h Italy
029h Switzerland
02Ah Czechoslovakia/Tjekia (not supported by DR-DOS 5.0)
02Bh Austria (DR-DOS 5.0)
02Ch United Kingdom
02Dh Denmark
02Eh Sweden
02Fh Norway
030h Poland (not supported by DR-DOS 5.0)
031h Germany
037h Brazil (not supported by DR-DOS 5.0)
03Dh International English [Australia in DR-DOS 5.0]
051h Japan (DR-DOS 5.0, MS-DOS 5.0+)
052h Korea (DR-DOS 5.0)
056h China (MS-DOS 5.0+)
058h Taiwan (MS-DOS 5.0+)
05Ah Turkey (MS-DOS 5.0+)
15Fh Portugal
162h Iceland
166h Finland
311h Middle East/Saudi Arabia (DR-DOS 5.0,MS-DOS 5.0+)
3CCh Israel (DR-DOS 5.0,MS-DOS 5.0+)
--------D-2138--DXFFFF-----------------------
INT 21 - DOS 3+ - SET COUNTRY CODE
AH = 38h
DX = FFFFh
AL = 01h thru FEh for specific country with code <255
AL = FFh for specific country with code >= 255
BX = 16-bit country code (see #0556)
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
Note: not supported by OS/2
SeeAlso: INT 2F/AX=1403h
--------D-2139-------------------------------
INT 21 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY
AH = 39h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h) (see #0811 at AH=59h)
Notes: all directories in the given path except the last must exist
fails if the parent directory is the root and is full
DOS 2.x-3.3 allow the creation of a directory sufficiently deep that
it is not possible to make that directory the current directory
because the path would exceed 64 characters
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Ah,AH=3Bh,AH=6Dh,AH=71h,AH=E2h/SF=0Ah,INT 2F/AX=1103h
SeeAlso: INT 60/DI=0511h
--------D-213A-------------------------------
INT 21 - DOS 2+ - "RMDIR" - REMOVE SUBDIRECTORY
AH = 3Ah
DS:DX -> ASCIZ pathname of directory to be removed
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h,06h,10h) (see #0811 at AH=59h)
Notes: directory must be empty (contain only '.' and '..' entries)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=39h,AH=3Bh,AH=71h,AH=E2h/SF=0Bh,INT 2F/AX=1101h,INT 60/DI=0512h
--------D-213B-------------------------------
INT 21 - DOS 2+ - "CHDIR" - SET CURRENT DIRECTORY
AH = 3Bh
DS:DX -> ASCIZ pathname to become current directory (max 64 bytes)
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h) (see #0811 at AH=59h)
Notes: if new directory name includes a drive letter, the default drive is
not changed, only the current directory on that drive
changing the current directory also changes the directory in which
FCB file calls operate
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=47h,AH=71h,INT 2F/AX=1105h
--------D-213C-------------------------------
INT 21 - DOS 2+ - "CREAT" - CREATE OR TRUNCATE FILE
AH = 3Ch
CX = file attributes (see #0557)
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (03h,04h,05h) (see #0811 at AH=59h)
Notes: if a file with the given name exists, it is truncated to zero length
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
DR-DOS checks the system password or explicitly supplied password at
the end of the filename against the reserved field in the directory
entry before allowing access
SeeAlso: AH=16h,AH=3Dh,AH=5Ah,AH=5Bh,AH=93h,INT 2F/AX=1117h

Bitfields for file attributes:
Bit(s) Description (Table 0557)
0 read-only
1 hidden
2 system
3 volume label (ignored)
4 reserved, must be zero (directory)
5 archive bit
7 if set, file is shareable under Novell NetWare
--------D-213D-------------------------------
INT 21 - DOS 2+ - "OPEN" - OPEN EXISTING FILE
AH = 3Dh
AL = access and sharing modes (see #0558)
DS:DX -> ASCIZ filename
CL = attribute mask of files to look for (server call only)
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (01h,02h,03h,04h,05h,0Ch,56h) (see #0811 at AH=59h)
Notes: file pointer is set to start of file
file handles which are inherited from a parent also inherit sharing
and access restrictions
files may be opened even if given the hidden or system attributes
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
DR-DOS checks the system password or explicitly supplied password at
the end of the filename against the reserved field in the directory
entry before allowing access
sharing modes are only effective on local drives if SHARE is loaded
SeeAlso: AH=0Fh,AH=3Ch,AX=4301h,AX=5D00h,INT 2F/AX=1116h,INT 2F/AX=1226h

Bitfields for access and sharing modes:
Bit(s) Description (Table 0558)
2-0 access mode
000 read only
001 write only
010 read/write
011 (DOS 5+ internal) passed to redirector on EXEC to allow
case-sensitive filenames
3 reserved (0)
6-4 sharing mode (DOS 3+)
000 compatibility mode
001 "DENYALL" prohiboth read and write access by others
010 "DENYWRITE" prohiwrite access by others
011 "DENYREAD" prohiread access by others
100 "DENYNONE" allow full access by others
111 network FCB (only available during server call)
7 inheritance
if set, file is private to current process and will not be inherited
by child processes

(Table 0559)
Values of DOS file sharing behavior:
| Second and subsequent Opens
First |Compat Deny Deny Deny Deny
Open | All Write Read None
|R W RW R W RW R W RW R W RW R W RW
- - - - -| - - - - - - - - - - - - - - - - -
Compat R |Y Y Y N N N 1 N N N N N 1 N N
W |Y Y Y N N N N N N N N N N N N
RW|Y Y Y N N N N N N N N N N N N
- - - - -|
Deny R |C C C N N N N N N N N N N N N
All W |C C C N N N N N N N N N N N N
RW|C C C N N N N N N N N N N N N
- - - - -|
Deny R |2 C C N N N Y N N N N N Y N N
Write W |C C C N N N N N N Y N N Y N N
RW|C C C N N N N N N N N N Y N N
- - - - -|
Deny R |C C C N N N N Y N N N N N Y N
Read W |C C C N N N N N N N Y N N Y N
RW|C C C N N N N N N N N N N Y N
- - - - -|
Deny R |2 C C N N N Y Y Y N N N Y Y Y
None W |C C C N N N N N N Y Y Y Y Y Y
RW|C C C N N N N N N N N N Y Y Y
Legend: Y = open succeeds, N = open fails with error code 05h
C = open fails, INT 24 generated
1 = open succeeds if file read-only, else fails with error code
2 = open succeeds if file read-only, else fails with INT 24
--------v-213DFF-----------------------------
INT 21 - VIRUS - "JD-448" - INSTALLATION CHECK
AX = 3DFFh
Return: AX = 4A44h if resident
SeeAlso: AX=357Fh,AX=4203h
--------D-213E-------------------------------
INT 21 - DOS 2+ - "CLOSE" - CLOSE FILE
AH = 3Eh
BX = file handle
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (06h) (see #0811 at AH=59h)
Note: if the file was written to, any pending disk writes are performed, the
time and date stamps are set to the current time, and the directory
entry is updated
SeeAlso: AH=10h,AH=3Ch,AH=3Dh,INT 2F/AX=1106h,INT 2F/AX=1227h
--------D-213F-------------------------------
INT 21 - DOS 2+ - "READ" - READ FROM FILE OR DEVICE
AH = 3Fh
BX = file handle
CX = number of bytes to read
DS:DX -> buffer for data
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Notes: data is read beginning at current file position, and the file position
is updated after a successful read
the returned AX may be smaller than the request in CX if a partial
read occurred
if reading from CON, read stops at first CR
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
BUG: Novell NETX.EXE v3.26 and 3.31 do not set CF if the read fails due to
a record lock (see AH=5Ch), though it does return AX=0005h; this
has been documented by Novell
SeeAlso: AH=27h,AH=40h,AH=93h,INT 2F/AX=1108h,INT 2F/AX=1229h
--------G-213F-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - READ STATUS BLOCK
AH = 3Fh
BX = handle for character device "TDHDEBUG"
CX = number of bytes to read
DS:DX -> buffer for status block (see #0561)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
SeeAlso: AH=40h"Turbo Debug"

(Table 0560)
Values for status of Turbo Debugger command:
00h successful
01h invalid handle
02h no more breakpoints available
03h hardware does not support specified breakpoint type
04h previous command prevents execution
05h debugger hardware not found
06h hardware failure
07h invalid command
08h driver not initialized yet
FEh recursive entry (hardware breakpoint inside hw bp handler)

Format of Turbo Debugger status block:
Offset Size Description (Table 0561)
00h BYTE status of command (see #0560)
---status for command 01h---
01h WORD device driver interface version number (currently 1)
03h WORD device driver software version
05h BYTE maximum simultaneous hardware breakpoints
06h BYTE configuration bits (see #0562)
07h BYTE supported breakpoint types (see #0563)
08h WORD supported addressing match modes (see #0564)
0Ah WORD supported data matches (see #0565)
0Ch BYTE maximum data match length (01h, 02h, or 04h)
0Dh WORD size of onboard memory (in KB)
0Fh WORD maximum number of trace-back events
11h WORD hardware breakpoint enable byte address segment (0000h if not
supported)
---status for command 04h---
01h BYTE handle to use when referring to the just-set breakpoint

Bitfields for Turbo Debugger configuration bits:
Bit(s) Description (Table 0562)
0 CPU and DMA accesses are distinct
1 can detect DMA transfers
2 supports data mask
3 hardware pass counter on breakpoints
4 can match on data as well as addresses

Bitfields for Turbo Debugger supported breakpoint types:
Bit(s) Description (Table 0563)
0 memory read
1 memory write
2 memory read/write
3 I/O read
4 I/O write
5 I/O read/write
6 instruction fetch

Bitfields for Turbo Debugger supported addressing match modes:
Bit(s) Description (Table 0564)
0 any address
1 equal to test value
2 not equal
3 above test value
4 below test value
5 below or equal
6 above or equal
7 within range
8 outside range

Bitfields for Turbo Debugger supported data matches:
Bit(s) Description (Table 0565)
0 any data
1 equal to test value
2 not equal
3 above test value
4 below test value
5 below or equal
6 above or equal
7 within range
8 outside range
--------N-213F-------------------------------
INT 21 - PC/TCP IPCUST.SYS - READ CONFIGURATION DATA
AH = 3Fh
BX = handle for character device "$IPCUST"
CX = number of bytes to read
DS:DX -> buffer for configuration data (see #0566)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
v2.1+ uses a new configuration method, but allows the installation
of IPCUST.SYS for backward compatibility with other software which
must read the PC/TCP configuration
SeeAlso: AH=40h"IPCUST",AX=4402h"IPCUST",AX=4402h"FTPSOFT"

Format of PC/TCP configuration data:
Offset Size Description (Table 0566)
00h 12 BYTEs IPCUST.SYS device driver header
12h BYTE ???
13h BYTE ???
14h WORD ???
16h BYTE bit flags
bit 0: send BS rather than DEL for BackSpace key
bit 1: wrap long lines
17h BYTE ???
18h 64 BYTEs ASCIZ hostname
58h 64 BYTEs ASCIZ domain name
(fully qualified domain name is hostname.domain-name)
98h 16 BYTEs ASCIZ username
A8h 64 BYTEs ASCIZ full name
E8h 64 BYTEs ASCIZ office address
128h 32 BYTEs ASCIZ phone number
148h WORD offset from GMT in minutes
14Ah 4 BYTEs ASCIZ timezone name
14Eh WORD number of time servers
150h ? DWORDs (big-endian) IP addresses for time servers
???
164h WORD number of old-style name servers
166h 3 DWORDs (big-endian) IP addresses for name servers
172h WORD number of domain name servers
174h 3 DWORDs (big-endian) IP addresses for domain name servers
180h DWORD (big-endian) IP address of default gateway
184h DWORD (big-endian) IP address of log server
188h DWORD (big-endian) IP address of cookie server
18Ch DWORD (big-endian) IP address of lpr server
190h DWORD (big-endian) IP address of imagen print server
194h 54 BYTEs ???
1E8h WORD TCP default window size in bytes
1EAh WORD TCP low window size
1ECh 64 BYTEs ASCIZ host tabel filename
22Ch 2 BYTEs ???
22Eh 80 BYTEs ASCIZ mail relay host name
27Eh BYTE ???
27Fh BYTE ??? bit flags
280h 44 BYTEs ???
2ACh WORD ???
2AEh 202 BYTEs ???
--------N-213F-------------------------------
INT 21 - WORKGRP.SYS - GET ENTRY POINT
AH = 3Fh
BX = file handle for device "NET$HLP$"
CX = 0008h
DS:DX -> buffer for entry point record (see #0636)
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Program: WORKGRP.SYS is the portion of Microsoft's Workgroup Connection which
permits communication with PCs running Windows for Workgroups or
LAN Manager
SeeAlso: AX=4402h"WORKGRP.SYS",INT 2F/AX=9400h
--------N-213F-------------------------------
INT 21 - BW-TCP - GET DRIVER INFO
AH = 3Fh
BX = file handle for device "ETHDEV27"
CX = 002Bh
DS:DX -> buffer for driver info (see #0567)
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Program: BW-TCP is a TCP/IP protocol stack by Beame & Whiteside Software
Notes: the B&W socket library performs an INT 21/AX=4401h with DX=0060h before
making this call to retrieve the driver information; one should also
call the private API interrupt with AH=15h
the installation check for the TCP/IP stack is to test for the
existence of the character device UDP-IP10
SeeAlso: INT 14/AH=56h,INT 62/AH=00h"ETHDEV",INT 63/AH=03h,INT 64/AH=00h
Index: installation check;BW-TCP hardware driver
Index: installation check;BW-TCP TCPIP.SYS

Format of BW-TCP driver info:
Offset Size Description (Table 0567)
00h WORD I/O base address
02h BYTE shared memory page (01h = segment 0100h, etc.)
03h BYTE interrupt vector for private API
04h BYTE IRQ used by board
05h WORD size of data buffer
07h WORD maximum transfer window
09h WORD time zone
0Bh BYTE address type (01h user, 04h RARP, 05h BOOTP)
0Ch DWORD internet address
10h WORD "value" ???
12h BYTE subnet mask
13h WORD "ether_pointer" ???
15h WORD offset in device driver of log server records
17h WORD offset in device driver of name server records
19h WORD offset in device driver of print server records
1Bh WORD offset in device driver of time server records
1Dh WORD offset in device driver of gateway records
1Fh WORD segment address of device driver
21h BYTE transfer size
22h 9 BYTEs network adapter board name
---11/21/91+ ---
23h BYTE ETHDEV version (major in high nybble, minor in low nybble)
24h BYTE ETHDEV revision
25h BYTE TCPIP version (major in high nybble, minor in low nybble)
26h BYTE TCPIP revision
27h BYTE BWRPC version (major in high nybble, minor in low nybble)
28h BYTE BWRPC revision
29h BYTE BWNFS version (major in high nybble, minor in low nybble)
2Ah BYTE BWNFS revision
2Bh BYTE Telnet version (major in high nybble, minor in low nybble)
2Ch BYTE Telnet revision
2Dh BYTE NETBIOS version (major in high nybble, minor in low nybble)
2Eh BYTE NETBIOS revision
Note: for each driver, if version=0, the driver is not installed or does
not support the version check

Format of BW-TCP server records:
Offset Size Description (Table 0568)
00h BYTE number of server records following
01h N DWORDs internet addresses of servers
--------y-213F-------------------------------
INT 21 - Trusted Access - NB.SYS - GET STATE
AH = 3Fh
BX = file handle for device "$$NB$$NB"
CX = 0002h (size of state)
DS:DX -> buffer for state record (see #0569)
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Program: Trusted Access is a security and access-control package by Lassen
Software, Inc.; NB.SYS is a device driver to prevent the user from
terminating CONFIG.SYS or AUTOEXEC.BAT with Ctrl-Break
SeeAlso: AH=40h"NB.SYS",AX=4101h

Format of Trusted Access state record:
Offset Size Description (Table 0569)
00h BYTE 00h off, 01h on
01h BYTE keys being disabled
bit 0: Ctrl-Break
bit 1: SysReq
bit 2: Ctrl and Alt
bit 3: Ctrl-Alt-Del
bit 7: all keys (overrides other bits)
----------213F-------------------------------
INT 21 U - IFSHLP.SYS - GET ENTRY POINT
AH = 3Fh
BX = file handle for device "IFS$HLP$"
CX = 0008h (size of buffer in bytes)
DS:DX -> buffer for entry point record (see #0570)
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Program: IFSHLP.SYS is a support driver for Microsoft Windows for Workgroups
SeeAlso: AX=4402h"IFSHLP"

Format of IFSHLP.SYS entry point record:
Offset Size Description (Table 0570)
00h 4 BYTEs (call) signature 70h E9h 34h 37h
signature must be 34h 37h 70h EFh if called via IOCTL
04h DWORD (ret) pointer to FAR call entry point (see #0571)

(Table 0571)
Call IFSHLP.SYS entry point with:
STACK: WORD function number (00h-0Ch)
00h ???
01h set ??? intercept
02h remove ??? intercept
03h ??? LPT2
04h ??? LPT1
05h ??? and remove ??? intercept
06h set ??? flag
07h clear ??? flag
08h get ??? flag word
09h ???
0Ah ???
0Bh ???
0Ch get ???
---if function 00h---
Return: AX = ??? (0024h seen)
DX = resident code segment
---if function 01h---
STACK: DWORD new intercept address
Return: AX = status
0000h successful
0001h failed (already set)
DX = 0000h
---if function 02h---
Return: AX = status
0000h successful
0001h failed (not set)
DX = 0000h
---if function 03h,04h---
STACK: WORD ???
Return: AX = 0000h
DX = 0000h
---if function 05h---
???
---if function 06h---
Return: AX = 0001h and DX = 0000h if already set
AX,DX unchanged if successful
---if function 07h---
Return: AX = 0001h and DX = 0000h if not set
AX,DX unchanged if successful
---if function 08h---
Return: DX = 0000h
AX = flags (bit 0 set/cleared by functions 06h and 07h)
---if function 09h---
Return: AX = status
0000h successful
0001h failed (already called)
---if function 0Ah---
STACK: WORD ???
???
---if function 0Bh---
Return: AX = status
0000h successful
0001h failed (not set)
---if function 0Ch---
Return: AX = 0000h
ES:BX -> ??? data
---if function > 0Ch---
Return: AX = 0001h
DX = 0000h
--------D-2140-------------------------------
INT 21 - DOS 2+ - "WRITE" - WRITE TO FILE OR DEVICE
AH = 40h
BX = file handle
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Notes: if CX is zero, no data is written, and the file is truncated or
extended to the current position
data is written beginning at the current file position, and the file
position is updated after a successful write
the usual cause for AX < CX on return is a full disk
BUG: a write of zero bytes will appear to succeed when it actually failed
if the write is extending the file and there is not enough disk
space for the expanded file (DOS 5.0-6.0); one should therefore check
whether the file was in fact extended by seeking to 0 bytes from
the end of the file (INT 21/AX=4202h/CX=0/DX=0)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=28h,AH=3Fh,AH=93h,INT 2F/AX=1109h
--------G-2140-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - SEND CMD TO HARDWARE BRKPNT DRIVER
AH = 40h
BX = handle for character device "TDHDEBUG"
CX = number of bytes to write
DS:DX -> hardware breakpoint command (see #0572)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Note: results are retrieved by reading from the device
SeeAlso: AH=3Fh"Turbo Debug"

Format of Turbo Debugger hardware breakpoint commands:
Offset Size Description (Table 0572)
00h BYTE command code
00h install interrupt vectors
01h get hardware capabilities
02h enable hardware breakpoints
03h disable hardware breakpoints
04h set hardware breakpoint
05h clear hardware breakpoint
06h set I/O base address and reset hardware
07h restore interrupt vectors
---command code 00h---
01h DWORD pointer to Turbo Debugger entry point to be jumped to on
hardware breakpoint; call with CPU state the same as on
the breakpoint except for pushing AX and placing an entry
code (FFh if breakout button or breakpoint handle) in AH
---command code 04h---
01h BYTE breakpoint type
00h memory read
01h memory write
02h memory read/write
03h I/O read
04h I/O write
05h I/O read/write
06h instruction fetch
02h BYTE address matching mode (see #0573)
03h DWORD 32-bit linear low address
07h DWORD 32-bit linear high address
0Bh WORD pass count
0Dh BYTE data size (01h, 02h, or 04h)
0Eh BYTE source of matched bus cycle (01h CPU, 02h DMA, 03h either)
0Fh BYTE data-matching mode (see #0573)
10h DWORD low data value
14h DWORD high data value
18h DWORD data mask specifying which bits of the data are tested
---command code 05h---
01h BYTE handle of breakpoint to clear (breakpoint returned from command
04h)
---command code 06h---
01h WORD base address of hardware debugger board

(Table 0573)
Values for Turbo Debugger address/data matching mode:
00h match any
01h equal to test value
02h different from test value
03h above test value
04h below test value
05h below or equal to test value
06h above or equal to test value
07h within inclusive range
08h outside specified range
--------N-2140-------------------------------
INT 21 - PC/TCP IPCUST.SYS - WRITE CONFIGURATION DATA
AH = 40h
BX = handle for character device "$IPCUST"
CX = number of bytes to write
DS:DX -> buffer for configuration data (AH=3Fh"IPCUST")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
v2.1+ uses a new configuration method, but allows the installation
of IPCUST.SYS for backward compatibility with other software which
must read the PC/TCP configuration
SeeAlso: AH=3Fh"IPCUST",AX=4402h"IPCUST"
--------y-2140-------------------------------
INT 21 U - Trusted Access - NB.SYS - SET STATE
AH = 40h
BX = handle for character device "$$NB$$NB"
DS:DX -> state record (see #0569)
CX ignored
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see #0811 at AH=59h)
Program: Trusted Access is a security and access-control package by Lassen
Software, Inc.; NB.SYS is a device driver to prevent the user from
terminating CONFIG.SYS or AUTOEXEC.BAT with Ctrl-Break
SeeAlso: AH=3Fh"NB.SYS"
--------j-214000BX0002-----------------------
INT 21 - FARTBELL.EXE - INSTALLATION CHECK
AX = 4000h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Return: CF clear if installed
AX = CS of resident code
Program: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4001h
--------j-214001BX0002-----------------------
INT 21 - FARTBELL.EXE - FORCE NOISE
AX = 4001h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Program: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4000h
--------D-2141-------------------------------
INT 21 - DOS 2+ - "UNLINK" - DELETE FILE
AH = 41h
DS:DX -> ASCIZ filename (no wildcards, but see below)
CL = attribute mask for deletion (server call only, see below)
Return: CF clear if successful
AX destroyed (DOS 3.3) AL seems to be drive of deleted file
CF set on error
AX = error code (02h,03h,05h) (see #0811 at AH=59h)
Notes: (DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
the filespec must be canonical (as returned by AH=60h), and only
files matching the attribute mask in CL are deleted
DR-DOS 5.0-6.0 returns error code 03h if invoked via AX=5D00h
DOS does not erase the file's data; it merely becomes inaccessible
because the FAT chain for the file is cleared
deleting a file which is currently open may lead to filesystem
corruption. Unless SHARE is loaded, DOS does not close the handles
referencing the deleted file, thus allowing writes to a nonexistant
file.
under DRDOS and DR Multiuser DOS, this function will fail if the file
is currently open
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
BUG: DR-DOS 3.41 crashes if called via AX=5D00h
SeeAlso: AH=13h,AX=4301h,AX=4380h,AX=5D00h,AH=60h,AH=71h,AX=F244h
SeeAlso: INT 2F/AX=1113h
--------y-214101DXFFFE-----------------------
INT 21 - SoftLogic Data Guardian - ???
AX = 4101h
DX = FFFEh
Return: AX = 0000h if installed
Note: resident code sets several internal variables on this call
SeeAlso: AH=3Fh"NB.SYS",INT 16/AX=FFA3h/BX=0000h
--------D-2142-------------------------------
INT 21 - DOS 2+ - "LSEEK" - SET CURRENT FILE POSITION
AH = 42h
AL = origin of move
00h start of file
01h current file position
02h end of file
BX = file handle
CX:DX = offset from origin of new file position
Return: CF clear if successful
DX:AX = new file position in bytes from start of file
CF set on error
AX = error code (01h,06h) (see #0811 at AH=59h)
Notes: for origins 01h and 02h, the pointer may be positioned before the
start of the file; no error is returned in that case, but subsequent
attempts at I/O will produce errors
if the new position is beyond the current end of file, the file will
be extended by the next write (see AH=40h)
BUG: using this method to grow a file from zero bytes to a very large size
can corrupt the FAT in some versions of DOS; the file should first
be grown from zero to one byte and then to the desired large size
SeeAlso: AH=24h,INT 2F/AX=1228h
--------v-214203-----------------------------
INT 21 - VIRUS - "Shake" - INSTALLATION CHECK
AX = 4203h
Return: AX = 1234h if resident
SeeAlso: AX=3DFFh,AX=4243h
--------v-214243-----------------------------
INT 21 - VIRUS - "Invader" - INSTALLATION CHECK
AX = 4243h
Return: AX = 5678h if resident
SeeAlso: AX=4203h,AX=4B04h
--------D-214300-----------------------------
INT 21 - DOS 2+ - GET FILE ATTRIBUTES
AX = 4300h
DS:DX -> ASCIZ filename
Return: CF clear if successful
CX = file attributes (see #0574)
AX = CX (DR-DOS 5.0)
CF set on error
AX = error code (01h,02h,03h,05h) (see #0811 at AH=59h)
Notes: under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
under DR-DOS 3.41 and 5.0, attempts to change the subdirectory bit are
simply ignored without an error
BUG: Windows for Workgroups returns error code 05h (access denied) instead
of error code 02h (file not found) when attempting to get the
attributes of a nonexistent file. This causes open() with O_CREAT
and fopen() with the "w" mode to fail in Borland C++.
SeeAlso: AX=4301h,AX=4310h,AH=71h,AH=B6h,INT 2F/AX=110Fh,INT 60/DI=0517h
--------D-214301-----------------------------
INT 21 - DOS 2+ - "CHMOD" - SET FILE ATTRIBUTES
AX = 4301h
CX = new file attributes (see #0574)
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,02h,03h,05h) (see #0811 at AH=59h)
Notes: will not change volume label or directory attribute bits, but will
change the other attribute bits of a directory (the directory
bit must be cleared to successfully change the other attributes of a
directory, but the directory will not be changed to a normal file as
a result)
MS-DOS 4.01 reportedly closes the file if it is currently open
for security reasons, the Novell NetWare execute-only bit can never
be cleared; the file must be deleted and recreated
under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
DOS 5.0 SHARE will close the file if it is currently open in sharing-
compatibility mode, otherwise a sharing violation critical error is
generated if the file is currently open
SeeAlso: AX=4300h,AX=4311h,AH=71h,INT 2F/AX=110Eh

Bitfields for file attributes:
Bit(s) Description (Table 0574)
7 shareable (Novell NetWare)
6 unused
5 archive
4 directory
3 volume label
execute-only (Novell NetWare)
2 system
1 hidden
0 read-only
--------D-214302-----------------------------
INT 21 - DOS 7 (Chicago) - GET VOLUME INFORMATION
AX = 4302h
details not yet available
SeeAlso: AH=71h,AH=72h
--------O-214302-----------------------------
INT 21 - DR-DOS 3.41+ internal - GET ACCESS RIGHTS
AX = 4302h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
CX = access rights (see #0575)
AX = CX (DR-DOS 5.0)
CF set on error
AX = error code
Desc: Determine which operations the calling program may perform on a
specified file without being required to provide a password.
Notes: this protection scheme has been coordinated on all current Digital
Research/Novell operating systems (DR-DOS 3.41+, DRMDOS 5.x, and
FlexOS 2+)
this function is documented in DR-DOS 6.0 and corresponds to the
"Get/Set File Attributes" function, subfunction 2, documented in
Concurrent DOS.
only FlexOS actually uses the "execution" bits; DR-DOS 3.41+ treats
them as "read" bits.
DR-DOS 3.41-5.x only use bits 0-3. Only DR-DOS 6.0 using a
DRMDOS 5.x security system allowing for users and groups uses bits
4-11.
SeeAlso: AX=4303h

Bitfields for DR-DOS file access rights:
Bit(s) Description (Table 0575)
0 owner delete requires password
1 owner execution requires password (FlexOS)
2 owner write requires password
3 owner read requires password
4 group delete requires password
5 group execution requires password (FlexOS)
6 group write requires password
7 group read requires password
8 world delete requires password
9 world execution requires password (FlexOS)
10 world write requires password
11 world read requires password
--------O-214303-----------------------------
INT 21 - DR-DOS 3.41+ internal - SET ACCESS RIGHTS AND PASSWORD
AX = 4303h
CX = access rights
bits 11-0: access rights (see #0575)
bit 15: new password is to be set
DS:DX -> ASCIZ pathname
[DTA] = new password if CX bit 15 is set (blank-padded to 8 characters)
Return: CF clear if successful
CF set on error
AX = error code
Notes: if the file is already protected, the old password must be added after
the pathname, separated by a ";"
this function is documented in DR-DOS 6.0 and corresponds to the
"Get/Set File Attributes" function, subfunction 3, documented in
Concurrent DOS.
SeeAlso: AH=0Fh,AH=17h,AX=4302h"DR-DOS",AX=4305h,AX=4454h
--------O-214304-----------------------------
INT 21 U - DR-DOS 5.0-6.0 internal - GET ENCRYPTED PASSWORD
AX = 4304h
DS:DX -> ASCIZ filename
???
Return: CF clear if successful
CX = AX = 0000h if no password assigned to file
CF set on error
AX = error code (see #0811 at AH=59h)
Note: this function is only supported by DR-DOS 5.0 and 6.0 and DRMDOS 5.1
SeeAlso: AX=4303h,AX=4305h
--------O-214305-----------------------------
INT 21 U - DR-DOS 5.0-6.0 internal - SET EXTENDED FILE ATTRIBUTES
AX = 4305h
DS:DX -> ASCIZ filename
???
Return: CF clear if successful
CF set on error
AX = error code (see #0811 at AH=59h)
Desc: this function allows the extended attributes, and optionally the
encrypted password, of a file to be set.
Note: this function is only supported by DR-DOS 5.0 and 6.0 and DRMDOS 5.1
SeeAlso: AX=4304h,AX=4311h
--------O-214306-----------------------------
INT 21 - DR-DOS 6.0 - GET FILE OWNER
AX = 4306h
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX = CX = value set with AX=4307h
CF set on error
AX = error code (see #0811 at AH=59h)
SeeAlso: AX=4307h
--------O-214307-----------------------------
INT 21 - DR-DOS 6.0 - SET FILE OWNER
AX = 4307h
CX = ??? (owner identification number?)
DS:DX -> ASCIZ filename
Return: CF clear if successful
CF set on error
AX = error code (see #0811 at AH=59h)
SeeAlso: AX=4306h
--------N-214310-----------------------------
INT 21 - Banyan VINES 2.1+ - GET EXTENDED FILE ATTRIBUTES
AX = 4310h
DS:DX -> ASCIZ filename
Return: CF clear if successful
CH = attributes (see #0576)
CF set on error
AX = error code (01h,02h,03h,05h) (see #0811 at AH=59h)
Note: the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4300h,AX=4311h,AH=B6h,INT 2F/AX=110Fh
--------N-214311-----------------------------
INT 21 - Banyan VINES 2.1+ - SET EXTENDED FILE ATTRIBUTES
AX = 4311h
CH = new attributes (see #0576)
DS:DX -> ASCIZ filename
Return: CF clear if successful
CF set on error
AX = error code (01h,02h,03h,05h) (see #0811 at AH=59h)
Note: the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4301h,AX=4305h,AX=4310h,INT 2F/AX=110Eh

Bitfields for VINES extended file attributes:
Bit(s) Description (Table 0576)
7 unused
6 shareable
5 execute-only
4-0 unused
--------O-214380-----------------------------
INT 21 - Novell DOS 7 - UNDELETE PENDING DELETE FILE
AX = 4380h
???
Return: ???
SeeAlso: AH=41h,AX=4381h
--------O-214381-----------------------------
INT 21 - Novell DOS 7 - PURGE PENDING DELETE FILE
AX = 4381h
???
Return: ???
SeeAlso: AH=41h,AX=4380h
--------D-214400-----------------------------
INT 21 - DOS 2+ - IOCTL - GET DEVICE INFORMATION
AX = 4400h
BX = handle
Return: CF clear if successful
DX = device information word (see #0577)
AX destroyed
CF set on error
AX = error code (01h,05h,06h) (see #0811 at AH=59h)
Notes: value in DH corresponds to high byte of device driver's attribute word
if handle refers to a character device
Novell NetWare reportedly does not return a drive number in bits 5-0
for a disk file
SeeAlso: AX=4401h,INT 2F/AX=122Bh

Bitfields for device information word:
Bit(s) Description (Table 0577)
character device
14 device driver can process IOCTL requests (see AX=4402h)
13 output until busy supported
11 driver supports OPEN/CLOSE calls
7 set (indicates device)
6 EOF on input
5 raw (binary) mode
4 device is special (uses INT 29)
3 clock device
2 NUL device
1 standard output
0 standard input
disk file
15 file is remote (DOS 3+)
14 don't set file date/time on closing (DOS 3+)
11 media not removable
8 (DOS 4 only) generate INT 24 if no disk space on write or read past
end of file
7 clear (indicates file)
6 file has not been written
5-0 drive number (0 = A:)
--------D-214401-----------------------------
INT 21 - DOS 2+ - IOCTL - SET DEVICE INFORMATION
AX = 4401h
BX = handle (must refer to character device)
DX = device information word (see #0577)
(DH must be zero)
Return: CF clear if successful
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4400h,INT 2F/AX=122Bh
--------D-214402-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL
AX = 4402h
BX = file handle referencing character device
CX = number of bytes to read
DS:DX -> buffer
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: format of data is driver-specific (see below for some specific cases)
SeeAlso: AX=4400h,AX=4403h,AX=4404h,INT 2F/AX=122Bh
--------N-214402-----------------------------
INT 21 - Network Driver Interface Specification (NDIS) 2.0.1 - PROTOCOL MANAGER
AX = 4402h
BX = file handle for device "PROTMAN$"
CX = 000Eh (size of request block)
DS:DX -> request block (see #0578,#0579,#0580,#0581,#0582,#0586,#0587)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h"FTPSOFT"

Format of NDIS request block for GetProtocolManagerInfo:
Offset Size Description (Table 0578)
00h WORD 01h
02h WORD returned status (see #0588)
04h DWORD returned pointer to structure representing parsed user config
08h DWORD unused
0Ch WORD returned BCD version of NDIS on which Protocol Manager is based
SeeAlso: #0579,#0580,#0581,#0582,#0583,#0584,#0585,#0586,#0587

Format of NDIS request block for RegisterModule:
Offset Size Description (Table 0579)
00h WORD 02h
02h WORD returned status (see #0588)
04h DWORD pointer to module's common characteristics table (see #0589)
08h DWORD pointer to list of modules to which the module is to be bound
0Ch WORD unused
SeeAlso: #0578,#0580,#0581,#0582,#0583,#0584,#0585,#0586,#0587

Format of NDIS request block for BindAndStart:
Offset Size Description (Table 0580)
00h WORD 03h
02h WORD returned status (see #0588)
04h DWORD caller's virtual address in FailingModules structure
08h DWORD unused
0Ch WORD unused
SeeAlso: #0578,#0579,#0581,#0582,#0583,#0584,#0585,#0586,#0587

Format of NDIS request block for GetProtocolManagerLinkage:
Offset Size Description (Table 0581)
00h WORD 04h
02h WORD returned status (see #0588)
04h DWORD returned dispatch point
08h DWORD unused
0Ch WORD returned protocol manager DS
Note: the dispatch point may be called as follows instead of using this IOCTL
STACK: WORD protocol manager DS
DWORD pointer to request block
Return: AX = returned status
STACK popped
SeeAlso: #0578,#0579,#0580,#0582,#0583,#0584,#0585,#0586,#0587

Format of NDIS request block for GetProtocolIniPath:
Offset Size Description (Table 0582)
00h WORD 05h
02h WORD returned status (see #0588)
04h DWORD pointer to a buffer for the ASCIZ pathname of PROTOCOL.INI
08h DWORD unused
0Ch WORD buffer length
SeeAlso: #0578,#0579,#0580,#0581,#0583,#0584,#0585,#0586,#0587

Format of NDIS request block for RegisterProtocolManagerInfo:
Offset Size Description (Table 0583)
00h WORD 06h
02h WORD returned status (see #0588)
04h DWORD pointer to structure containing parsed user config file
08h DWORD unused
0Ch WORD length of structure
SeeAlso: #0578,#0579,#0580,#0581,#0582,#0584,#0585,#0586,#0587

Format of NDIS request block for InitAndRegister:
Offset Size Description (Table 0584)
00h WORD 07h
02h WORD returned status (see #0588)
04h DWORD unused
08h DWORD poitner to ASCIZ name of the module to be prebind initialized
0Ch WORD unused
SeeAlso: #0578,#0579,#0580,#0581,#0582,#0583,#0585,#0586,#0587

Format of NDIS request block for UnbindAndStop:
Offset Size Description (Table 0585)
00h WORD 08h
02h WORD returned status (see #0588)
04h DWORD failing modules as for BindAndStart
08h DWORD if not 0000h:0000h, pointer to ASCIZ name of module to unbind
if 0000h:0000h, terminate a set of previously dynamically
bound protocol modules
0Ch WORD unused
SeeAlso: #0578,#0579,#0580,#0581,#0582,#0583,#0584,#0586,#0587

Format of NDIS request block for BindStatus:
Offset Size Description (Table 0586)
00h WORD 09h
02h WORD returned status (see #0588)
04h DWORD must be 0000h:0000h
on return, points to root tree
08h DWORD 0000h:0000h
0Ch WORD unused under DOS
SeeAlso: #0578,#0579,#0580,#0581,#0582,#0583,#0584,#0585,#0587

Format of NDIS request block for RegisterStatus:
Offset Size Description (Table 0587)
00h WORD 0Ah
02h WORD returned status (0000h, 0008h, 002Ch) (see #0588)
04h DWORD 0000h:0000h
08h DWORD pointer to 16-byte ASCIZ module name
0Ch WORD 0000h
Note: not supported by the 10NET v5.0 PROTMAN$ driver
SeeAlso: #0578,#0579,#0580,#0581,#0582,#0583,#0584,#0585,#0586

(Table 0588)
Values for NDIS status code:
0000h success
0001h wait for release--protocol has retained control of the data buffer
0002h request queued
0003h frame not recognized
0004h frame rejected
0005h frame should be forwarded
0006h out of resource
0007h invalid parameter
0008h invalid function
0009h not supported
000Ah hardware error
000Bh transmit error
000Ch unrecognized destination
000Dh buffer too small
0020h already started
0021h binding incomplete
0022h driver not initialized
0023h hardware not found
0024h hardware failure
0025h configuration failure
0026h interrupt conflict
0027h MAC incompatible
0028h initialization failed
0029h no binding
002Ah network may be disconnected
002Bh incompatible OS version
002Ch already registered
002Dh path not found
002Eh insufficient memory
002Fh info not found
00FFh general failure
F000h-FFFFh reserved for vendor-specific codes, treated as general failure

Format of NDIS common characteristics table:
Offset Size Description (Table 0589)
00h WORD size of table in bytes
02h BYTE NDIS major version
03h BYTE NDIS minor version
04h WORD reserved
06h BYTE module major version
07h BYTE module minor version
08h DWORD module function flag bits
bit 0: binding at upper boundary supported
bit 1: binding at lower boundary supported
bit 2: dynamically bound
bits 3-31 reserved, must be 0
0Ch 16 BYTEs ASCIZ module name
1Ch BYTE upper boundary protocol level (see #0590)
1Dh BYTE upper boundary interface type
for MACs: 1 = MAC
for data links and transports: to be defined
for session: 1 = NCB
any level: 0 = private (ISV-defined)
1Eh BYTE lower boundary protocol level (see #0590)
1Fh BYTE lower boundary interface type
same as offset 1Dh
20h WORD module ID filled in by protocol manager
22h WORD module DS
24h DWORD system request entry point
28h DWORD pointer to service-specific characteristics (see #0592,#0594)
0000h:0000h if none
2Ch DWORD pointer to service-specific status, or 0000h:0000h if none
30h DWORD pointer to upper dispatch table (see #0591)
0000h:0000h if none
34h DWORD pointer to lower dispatch table (see #0591)
0000h:0000h if none
38h 2 DWORDs reserved, must be 0
Note: for compatibility with NDIS 1.x.x, a major version of 00h is
interpreted as 01h

(Table 0590)
Values for NDIS boundary protocol level:
00h physical
01h Media Access Control
02h Data link
03h network
04h transport
05h session
FFh not specified

Format of NDIS dispatch table:
Offset Size Description (Table 0591)
00h DWORD -> common characteristics table (see #0589)
04h 4 BYTEs ???
08h DWORD -> ??? function (called with 12 bytes of stack arguments)
0Ch DWORD -> ??? function (called with 10 bytes of stack arguments)
10h DWORD -> ??? function (called with 16 bytes of stack arguments)
14h DWORD -> ??? function (called with 4 bytes of stack arguments)
18h DWORD -> ??? function (called with 18 bytes of stack arguments)
1Ch DWORD -> ??? function (called with 12 bytes of stack arguments)

Format of MAC Service-Specific Characteristics Table:
Offset Size Description (Table 0592)
00h WORD length of table in bytes
02h 16 BYTEs ASCIZ MAC type name, "802.3", "802.4", "802.5", "802.6", "DIX",
"DIX+802.3", "APPLETALK", "ARCNET", "FDDI", "SDLC", "BSC",
"HDLC", or "ISDN"
12h WORD length of station addresses in bytes
14h 16 BYTEs permanent station address
24h 16 BYTEs current station address
34h DWORD current functional adapter address (00000000h if none)
38h DWORD pointer to multicast address list
3Ch DWORD link speed in bits/sec
40h DWORD service flags (see #0593)
44h WORD maximum frame size which may be both sent and received
46h DWORD total transmit buffer capacity in bytes
4Ah WORD transmit buffer allocation block size in bytes
4Ch DWORD total receive buffer capacity in bytes
50h WORD receive buffer allocation block size in bytes
52h 3 BYTEs IEEE vendor code
55h BYTE vendor adapter code
56h DWORD pointer to ASCIZ vendor adapter description
5Ah WORD IRQ used by adapter
5Ch WORD transmit queue depth
5Eh WORD maximum supported number of data blocks in buffer descriptors
60h N BYTEs vendor-specific info

Bitfields for service flags:
Bit(s) Description (Table 0593)
0 supports broadcast
1 supports multicast
2 supports functional/group addressing
3 supports promiscuous mode
4 station address software settable
5 statistics always current
6 supports InitiateDiagnostics
7 supports loopback
8 MAC does primarily ReceiveChain indications instead of ReceiveLookahead
indications
9 supports IBM source routing
10 supports MAC reset
11 supports Open/Close adapter
12 supports interrupt request
13 supports source routing bridge
14 supports GDT virtual addresses (OS/2 version)
15 multiple TransferDatas allowed durign a single indication
16 MAC normally sets FrameSize = 0 in ReceiveLookahead
17-31 reserved, must be 0

Format of NetBIOS Service-Specific Characteristics Table:
Offset Size Description (Table 0594)
00h WORD length of table in bytes
02h 16 BYTEs ASCIZ type name of NetBIOS module
12h WORD NetBIOS module code
14h N BYTEs vendor-specific info

Format of MAC Service-Specific Status Table:
Offset Size Description (Table 0595)
00h WORD length of table in bytes
02h DWORD seconds since 0:00 1/1/70 when diagnostics last run
(FFFFFFFFh = never)
06h DWORD MAC status bits (see #0596)
0Ah WORD current packet filter flags (see #0597)
0Ch DWORD pointer to media-specific status table or 0000h:0000h
10h DWORD seconds past 0:00 1/1/70 of last ClearStatistics
14h DWORD total frames received (FFFFFFFFh = not counted)
18h DWORD frames with CRC error (FFFFFFFFh = not counted)
1Ch DWORD total bytes received (FFFFFFFFh = not counted)
20h DWORD frames discarded--no buffer space (FFFFFFFFh = not counted)
24h DWORD multicast frames received (FFFFFFFFh = not counted)
28h DWORD broadcast frames received (FFFFFFFFh = not counted)
2Ch DWORD frames with errors (FFFFFFFFh = not counted)
30h DWORD overly large frames (FFFFFFFFh = not counted)
34h DWORD frames less than minimum size (FFFFFFFFh = not counted)
38h DWORD multicast bytes received (FFFFFFFFh = not counted)
3Ch DWORD broadcast bytes received (FFFFFFFFh = not counted)
40h DWORD frames discarded--hardware error (FFFFFFFFh = not counted)
44h DWORD total frames transmitted (FFFFFFFFh = not counted)
48h DWORD total bytes transmitted (FFFFFFFFh = not counted)
4Ch DWORD multicast frames transmitted (FFFFFFFFh = not counted)
50h DWORD broadcast frames transmitted (FFFFFFFFh = not counted)
54h DWORD broadcast bytes transmitted (FFFFFFFFh = not counted)
58h DWORD multicast bytes transmitted (FFFFFFFFh = not counted)
5Ch DWORD frames not transmitted--timeout (FFFFFFFFh = not counted)
60h DWORD frames not transmitted--hardware error (FFFFFFFFh = not countd)
64h N BYTEs vendor-specific info

Bitfields for MAC status bits:
Bit(s) Description (Table 0596)
0-2 operational status
000 hardware not installed
001 hardware failed startup diagnostics
010 hardware configuration problem
011 hardware fault
100 operating marginally due to soft faults
101 reserved
110 reserved
111 hardware fully operational
3 MAC bound
4 MAC open
5 diagnostics in progress
6-31 reserved

Bitfields for packet filter flags:
Bit(s) Description (Table 0597)
0 directed/multicast or group/functional
1 broadcast
2 promiscuous
3 all source routing
4-15 reserved, must be zero
--------I-214402-----------------------------
INT 21 U - IBM SYSTEM 36/38 WORKSTATION EMULATION - VDI.SYS - GET ???
AX = 4402h
BX = handle for character device "GDMS"
CX = number of bytes to read (>= 4)
DS:DX -> buffer (see #0598)
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
AX = number of bytes read

Format of System 36/38 emulator returned data:
Offset Size Description (Table 0598)
00h 4 BYTEs ???
04h DWORD pointer to ???
08h 4 BYTEs ???
--------m-214402-----------------------------
INT 21 U - LASTBYTE.SYS v1.19 - IOCTL - GET ??? TABLE
AX = 4402h
BX = handle for device "LA$TBYTE"
CX = 0004h
DS:DX -> DWORD to hold address of 39-byte table of ???
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
AX = number of bytes read
Program: LASTBYTE.SYS is part of the shareware "The Last Byte" memory
management package by Key Software Products
SeeAlso: AX=4402h"HIGHUMM"
--------m-214402-----------------------------
INT 21 - HIGHUMM.SYS v1.17+ - IOCTL - GET API ADDRESS
AX = 4402h
BX = handle for device "KSP$UMM"
CX = 0004h
DS:DX -> DWORD to hold entry point
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
AX = number of bytes read
Program: HIGHUMM.SYS is part of the shareware "The Last Byte" memory management
package by Key Software Products
SeeAlso: AX=4402h"LASTBYTE"

(Table 0599)
Call HIGHUMM.SYS entry point with:
AH = 00h allocate UMB (same as XMS function 10h) (see INT 2F/AX=4310h)
DX = size in paragraphs
Return: BX = segment number (if successful)
DX = size of requested block/size of largest block
AH = 01h deallocate UMB (same as XMS func 11h) (see INT 2F/AX=4310h)
DX = segment number of UMB
AH = 02h request a bank-switched memory block
DX = size in paragraphs
Return: BX = segment number (if successful)
DX = size of requested block/size of largest block
AH = 03h release a bank-switched memory block
DX = segment number
AH = 04h transfer data to/from high memory
DS:SI -> source
ES:DI -> destination
CX = length in bytes
Note: enables bank-switched memory, does the copy, then disables
bank-switched memory
AH = 05h get a word from bank-switched memory
ES:DI -> word to read
Return: DX = word
AH = 06h put a word to bank-switched memory
ES:DI -> word to write
DX = word
AH = 07h put a byte to bank-switched memory
ES:DI -> byte to write
DL = byte
AH = 08h enable bank-switched memory
DS:SI -> 6-byte status save area
AH = 09h disable bank-switched memory
DS:SI -> 6-byte save area from enable call (AH=08h)
AH = 0Ah assign name to UMB or high bank-switched block
DX = segment number
DS:SI -> 8-byte blank-padded name
AH = 0Bh locate UMB block by name
DS:SI -> 8-byte blank-padded name
Return: BX = segment number (if successful)
DX = size of block
AH = 0Ch locate bank-switched block by name
DS:SI -> 8-byte blank-padded name
Return: BX = segment number (if successful)
DX = size of block
Return: AX = status code
0001h successful
0000h failed
BL = error code
80h not implemented
B0h insufficient memory, smaller block available
B1h insufficient memory, no blocks available
B2h invalid segment number
Note: only functions 00h and 01h are always available; the remaining
functions are only enabled if the proper commandline switch is given
--------c-214402-----------------------------
INT 21 - SMARTDRV.SYS v3.x only - IOCTL - GET CACHE STATUS
AX = 4402h
BX = file handle for device "SMARTAAR"
CX = number of bytes to read (min 28h)
DS:DX -> buffer for status record (see #0600)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4403h"SMARTDRV",INT 2F/AX=4A10h/BX=0000h

Format of SMARTDRV status record:
Offset Size Description (Table 0600)
00h BYTE write-through flag (always 01h)
01h BYTE writes should be buffered (always 00h)
02h BYTE cache enabled if 01h
03h BYTE driver type (01h extended memory, 02h expanded)
04h WORD clock ticks between cache flushes (currently unused)
06h BYTE cache contains locked tracks if nonzero
07h BYTE flush cache on INT 19 reboot if nonzero
08h BYTE cache full track writes if nonzero
09h BYTE double buffering (for VDS) state (00h off, 01h on, 02h dynamic)
0Ah DWORD original INT 13 vector
0Eh BYTE minor version number
0Fh BYTE major version number
10h WORD unused
12h WORD sectors read \
14h WORD sectors already in cache > may be scaled rather than
16h WORD sectors already in track buffer / absolute counts
18h BYTE cache hit rate in percent
19h BYTE track buffer hit rate in percent
1Ah WORD total tracks in cache
1Ch WORD number of tracks in use
1Eh WORD number of locked tracks
20h WORD number of dirty tracks
22h WORD current cache size in 16K pages
24h WORD original (maximum) cache size in 16K pages
26h WORD minimum cache size in 16K pages
28h DWORD pointer to byte flag to increment for locking cache contents
--------d-214402-----------------------------
INT 21 - CD-ROM device driver - IOCTL INPUT
AX = 4402h
BX = file handle referencing character device for CD-ROM driver
CX = number of bytes to read
DS:DX -> control block (see #0602)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: the data returned depends on the first byte of the control block; the
remainder of the control block is filled by the driver
SeeAlso: AX=4403h"CD-ROM",INT 2F/AX=0802h

(Table 0601)
Values for CD-ROM data being requested:
00h device driver header address
01h drive head location
02h reserved
03h error statistics
04h audio channel info
05h raw drive bytes (uninterpreted and device-specific)
06h device status
07h sector size
08h volume size
09h media change status
0Ah audio disk info
0Bh audio track info
0Ch audio Q-Channel info
0Dh audio sub-channel info
0Eh UPC code
0Fh audio status info

Format of CD-ROM control block:
Offset Size Description (Table 0602)
00h BYTE data being requested (see #0601)
---function 00h---
01h DWORD device driver header address (see also AH=52h)
---function 01h---
01h BYTE addressing mode
00h HSG
01h Red Book
02h DWORD current location of drive's head
logical sector number in HSG mode
frame/second/minute/unused in Red Book mode
(HSG sector = minute * 4500 + second * 75 + frame - 150)
---function 03h---
01h N BYTEs undefined as of 5 Aug 88 specification
---function 04h---
01h BYTE input channel (0-3) for output channel 0
02h BYTE volume for output channel 0
03h BYTE input channel (0-3) for output channel 1
04h BYTE volume for output channel 1
05h BYTE input channel (0-3) for output channel 2
06h BYTE volume for output channel 2
07h BYTE input channel (0-3) for output channel 3
08h BYTE volume for output channel 3
Notes: output channels 0 and 1 are left and right, 2 and 3 are left prime and
right prime; a volume of 00h is off
the default setting is for each input channel to be assigned to the
same-numbered output channel at full (FFh) volume
---function 05h---
01h BYTE number of bytes read
02h 128 BYTEs buffer for drive bytes
---function 06h---
01h DWORD device parameters (see #0603)
---function 07h---
01h BYTE read mode
00h cooked
01h raw
02h WORD sector size in bytes
---function 08h---
01h DWORD volume size in sectors
---function 09h---
01h BYTE media change status
00h don't know
01h media unchanged
FFh media has been changed
---function 0Ah---
01h BYTE lowest audio track number
02h BYTE highest audio track number
03h DWORD start address of lead-out track (Red Book format)
--function 0Bh---
01h BYTE track number (set by caller)
02h DWORD starting point of track (Red Book format)
06h BYTE track control info
bits 15,14,12: track type (notice: bits not contiguous!)
000 two audio channels, no pre-emphasis
001 two audio channels with pre-emphasis
010 data track
100 four audio channels, no pre-emphasis
101 four audio channels with pre-emphasis
other reserved
bit 13: digital copy permitted
---function 0Ch---
01h BYTE CONTROL and ADR byte (as received from drive)
02h BYTE track number
03h BYTE point or index
04h BYTE minute \
05h BYTE second > running time within track
06h BYTE frame /
07h BYTE zero
08h BYTE "AMIN" or "PMIN" \
09h BYTE "ASEC" or "PSEC" > running time on disk
0Ah BYTE "AFRAME" or "PFRAME" /
---function 0Dh---
01h DWORD starting frame address (Red Book format)
05h DWORD transfer address
09h DWORD number of sectors to read
Note: copies 96 bytes of sub-channel info per sector into buffer
---function 0Eh---
01h BYTE CONTROL and ADR byte
02h 7 BYTEs UPC/EAN code (13 BCD digits,low-order nybble of last byte is 0)
09h BYTE zero
0Ah BYTE "AFRAME"
---function 0Fh---
??? documentation not yet available
01h WORD pause status (0000h not paused, 0001h paused)
03h DWORD audio play start address
07h DWORD ??? audio play length or end address

Bitfields for CD-ROM device parameters:
Bit(s) Description (Table 0603)
0 door open
1 door unlocked
2 supports raw reading in addition to cooked
3 writable
4 can play audio/video tracks
5 supports interleaving
6 reserved
7 supports prefetch requests
8 supports audio channel control
9 supports Red Book addressing in addition to HSG
10 audio is playing
11 no disk in drive
12 supports R-W subchannels
--------m-214402-----------------------------
INT 21 - Quarterdeck - QEMM-386 v5+ - GET API ENTRY POINT
AX = 4402h
BX = file handle for device "QEMM386$"
CX = 0004h
DS:DX -> DWORD buffer for API entry point
Return: CF clear if successful
buffer filled (see INT 67/AH=3Fh for entry point parameters)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: Quarterdeck recently (June 1993) documented this function, but the
documentation incorrectly states that it is only available for
QEMM 6+
SeeAlso: AX=4402h"HOOKROM",INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
--------Q-214402-----------------------------
INT 21 U - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE
AX = 4402h
BX = file handle for device "HOOKROM$"
CX = 0004h
DS:DX -> DWORD buffer for address of hooked vector table (see #0604)
Return: CF clear if successful
DS:DX buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h/SF=01h

Format of HOOKROM.SYS hooked vector table entry:
Offset Size Description (Table 0604)
00h 5 BYTEs FAR jump to actual interrupt handler
(end of table if first byte is not EAh)
05h BYTE interrupt vector number
--------d-214402-----------------------------
INT 21 - Advanced SCSI Programming Interface (ASPI) - INTERFACE
AX = 4402h
BX = file handle for device "SCSIMGR$"
CX = 0004h or 0005h (see notes)
DS:DX -> buffer for result (see #0605), set to zeros before call
Return: CF clear if successful
AX = 0004h or 0005h (see notes)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: the variant of the call requesting five bytes is an UNDOCUMENTED
extension supported by Adaptec's ASPI2DOS.SYS, ASPI4DOS.SYS, and
ASPI7DOS.SYS; if made of a host manager which does not support the
variant, only four bytes will be returned. If the variant is
supported, Adaptec's WINASPI.DLL assumes that the host manager is
an "advanced" one which operates in either real or protected mode
(and thus does not require a DPMI INT 31/AX=0301h call to be invoked
from protected mode). Support of the five-byte variant also appears
to imply that an advanced ASPI host manager uses no temporary storage
space except the SRB and the stack, and that it is fully reentrant.
if called with a standard request for four bytes, even Adaptec's
advanced drivers return only the requested four bytes containing the
ASPI entry point address
the function address is called with the address of a SCSI Request
Block on the stack and the caller must clean up the stack
SeeAlso: AX=440Ch"ASPITAPE",INT 11/AH=FFh"WD7000"

Format of ASPI IOCTL result:
Offset Size Description (Table 0605)
00h DWORD function address
04h BYTE number of SCSI host adapters supported by host manager

(Table 0606)
Values for ASPI request number:
00h "HA_INQ" host adapter inquiry
01h "GET_TYPE" get device type
02h "EXEC_SIO" execute SCSI I/O
03h "ABORT_SRB" abort SRB
04h "RESET_DEV" reset SCSI device
05h "SET_HAPRMS" set host adapter parameters
06h get disk drive information

Format of SCSI Request Block (64 bytes):
Offset Size Description (Table 0607)
00h BYTE request number (see #0606)
01h BYTE request status (see #0608)
02h BYTE host adapter ID
03h BYTE request flags (see #0609)
04h DWORD reserved
---request 00h---
08h BYTE (return) number of host adapters
09h BYTE (return) target adapter ID
0Ah 16 BYTEs (return) SCSI manager ID
1Ah 16 BYTEs (return) host adapter ID
2Ah 16 BYTEs (return) host adapter-unique parameters
---request 01h---
08h BYTE target ID
09h BYTE logical unit number
0Ah BYTE (return) device type (see #0612)
---request 02h---
08h BYTE target ID
09h BYTE logical unit number
0Ah DWORD data allocation length
0Eh BYTE sense allocation length
0Fh DWORD data buffer pointer
13h DWORD next request pointer (for linking)
17h BYTE CDB length
18h BYTE (return) host adapter status (see #0607)
19h BYTE (return) target status (see #0611)
1Ah DWORD post routine address
1Eh WORD real mode Post DS
20h DWORD SRB pointer
24h WORD reserved
26h DWORD SRB physical address
2Ah 22 BYTEs SCSIMGR$ workspace
40h N BYTEs CCB, including sense data (20-24 bytes)
---request 03h---
08h DWORD address of SRB to abort
---request 04h---
08h BYTE target ID
09h BYTE logical unit number
0Ah 14 BYTEs reserved
18h BYTE (return) host adapter status (see #0610)
19h BYTE (return) target status (see #0611)
1Ah DWORD post routine address
1Eh 34 BYTEs workspace
---request 05h---
08h 16 BYTEs host adapter-unique parameters
---request 06h---
08h BYTE target ID
09h BYTE logical unit number
0Ah BYTE disk drive flags
0Bh BYTE INT 13h drive number
0Ch BYTE preferred head number translation
0Dh BYTE preferred sector size translation
0Eh 10 BYTEs reserved

(Table 0608)
Values for ASPI request status:
00h not done yet
01h completed successfully
02h aborted by host
04h SCSI I/O error
80h invalid
81h no adapter
82h no device attached
else status

Bitfields for ASPI request flags:
Bit(s) Description (Table 0609)
0 posting enabled
1 linking enabled
2 direction
3 transfer from SCSI target to host
4 transfer from host to SCSI target
Note: no data is transferred if both bits 3 and 4 are set

(Table 0610)
Values for host adapter status:
00h no error detected
11h select timeout
12h data overrun
13h bus error
14h bus failure

(Table 0611)
Values for target status:
00h no status
02h sense data stored in SRB
08h target busy
18h reservation error

(Table 0612)
Values for device type:
00h disk drive
01h tape drive (streamer)
02h printer
03h processor
04h WORM drive
05h CD-ROM drive
06h scanner
07h optical drive
08h autochanger
09h communications device

(Table 0613)
Values for disk drive flags:
00h no INT 13 access
01h INT 13 with DOS access
02h INT 13 without DOS access
03h invalid flags

Format of CCB:
Offset Size Description (Table 0614)
00h BYTE command code (see #0615)
01h BYTE flags
bits 4-0: vary by function
bits 7-5: logical unit number
02h BYTE "adr_1"
03h BYTE "adr_0"
04h BYTE length
05h BYTE control
...
06h/0Ah 14 BYTEs buffer for sense data (see #0616)

(Table 0615)
Values for CCB command code:
00h test unit ready
01h rewind
03h request sense data
05h get block size limits
08h Group 0 read
0Ah Group 0 write
10h write file marks
11h SCSI Space (set position?)
12h SCSI Inquire
15h set mode information
16h reserve SCSI device
17h release SCSI device
19h erase
1Ah request mode information
1Bh load/unload media
1Dh request target self-check
24h set window parameters
25h get window parameters
28h Group 1 read
2Ah Group 1 write
31h document feeder control
34h get scan data status
---vendor-specific commands---
D3h get document feeder status
D4h set document feeder mode

Format of sense data:
Offset Size Description (Table 0616)
00h BYTE error code (bit 7 set if valid)
01h BYTE segment number
02h BYTE sense key
bit 6: EOM
bit 5: ILI
bits 0-3: sense key (see #0617)
03h 4 BYTEs information bytes
07h BYTE additional sense length (0Ah)
08h 4 BYTEs command-specific information
0Ch BYTE additional sense code
0Dh BYTE additional sense code qualifier
0Eh BYTE field replaceable unit code
0Fh 3 BYTEs sense key specific bytes

(Table 0617)
Values for sense key:
00h no sense data
02h SCSI unit not ready
03h media error
04h unrecoverable hardware error
05h illegal parameter in CDB
06h target has been reset
0Bh target aborted command
--------m-214402-----------------------------
INT 21 U - Qualitas 386MAX v6.00+ - IOCTL INPUT - GET STATE
AX = 4402h
BX = file handle for device "386MAX$$"
CX = number of bytes to read
DS:DX -> BYTE 03h followed by 386MAX state buffer (see #0618)
Return: CF clear if successful
buffer at DS:DX+1 filled
AX = number of bytes actually copied
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: if the value given in CX is less than the size of the state record
(5Ah for v6.01, 66h for v7.00), only a partial state record will be
returned
the state is 40h bytes for 386MAX (actually ASTEMM) v2.20 ("386MAX$$"
did not exist yet, use "QMMXXXX0" and then "EMMXXXX0" instead) and
56h bytes for v5.11.
to invoke 386MAX API functions, push DX onto the stack, load DX with
the word at offset 25h in the returned state, load all other
registers as needed for the desired function, and execute an
OUT DX,AL or OUT DX,AX; DX will be set to the pushed value on return
if it is not otherwise modified by the API function. For safety,
in case a function is not supported or 386MAX is not present, SP
should be saved and restored around the API call.
Windows 3.1 Standard mode, LAN Manager, and Windows for Workgroups all
use the 386MAX API; LAN Manager and Windows for Workgroups reportedly
make some calls incorrectly
SeeAlso: AX=4403h/SF=03h"386MAX",INT 67/AH=3Fh

Format of 386MAX v6.01+ state:
Offset Size Description (Table 0618)
-1 BYTE (call) 03h
00h 6 BYTEs signature "386MAX"
06h 4 BYTEs version string "N;NN" or "N.NN" (i.e. "6;01" for v6.01)
(';' by default; apparently changed to a period when 386MAX
has linked high RAM into DOS's memory chain)
0Ah WORD segment of low-memory portion of 386MAX.SYS
0Ch 2 BYTEs ???
0Eh WORD segment of ??? memory block or 0000h
10h WORD bit flags 1 (see #0619)
12h WORD starting address of video memory in KB
14h 2 BYTEs ???
16h WORD total high DOS memory in KB
18h 2 BYTEs ???
1Ah WORD available shared memory in KB
1Ch WORD KBytes extended memory used by 386MAX
1Eh 2 BYTEs ???
20h WORD total extended memory in KB
22h WORD IO port to write (OUT DX,AL) to invoke 386MAX INT 15 functions
24h WORD IO port to write (OUT DX,AL) to invoke 386MAX API functions
26h WORD ??? (depends on DOS version)
28h WORD size of ??? in paragraphs
2Ah DWORD machine type (see #0627)
2Eh DWORD -> first DOS memory control block
32h WORD system configuration flags (see #0620)
34h WORD debugging flags 1 (see #0621)
36h WORD debugging flags 2 (see #0622)
38h 2 BYTEs ???
3Ah WORD segment of first MCB in high memory chain
3Ch WORD feature flags 1 (see #0624)
3Eh WORD feature flags 2 (see #0625)
40h WORD feature flags 3 (see #0626)
42h WORD segment of first 386MAX control block??? (see #0628)
44h WORD amount of memory to report available on INT 15/AH=88h
46h 4 BYTEs ???
4Ah WORD number of K at start of address space swapped with fast
extended memory (SWAP= parameter)
4Ch 2 BYTEs ???
4Eh WORD segment address of ???
50h WORD debugging flags 3 (see #0623)
52h DWORD old INT 21h
56h DWORD pointer to 386MAX's EMS (INT 67h) handler
---386MAX v7.00---
5Ah DWORD KB of extended memory managed by 386MAX
5Eh DWORD bytes of extended memory (EXT= parameter)
62h 4 BYTEs ???

Bitfields for 386MAX bit flags 1:
Bit(s) Description (Table 0619)
1 ???
2 allow A20 to be enabled/disabled???
3 ??? (cleared by calling INT 67 functions or starting MSWindows)
4 high RAM present???
5 386MAX in AUTO mode
6 386MAX enabled
7 386MAX is providing EMS services
8 ??? (affects API function 08h)
9 A20 gate closed (A20 disabled) (see INT 15/AX=2402h)
10 Weitek support enabled
11 ???
12 ROMs not shadowed???
13 QPMS has been used
14 ???
15 ???

Bitfields for 386MAX system configuration flags:
Bit(s) Description (Table 0620)
1 ROM compressed???
3 ???
5 386MAX loaded into high memory
6 Microchannel bus
7 Weitek math coprocessor detected
9 ??? (also generates INT 01 on ??? and INT 03 on ???)
11 PC/XT (thus only single 8259 interrupt controller present, DMA only
in 1st megabyte, etc)
13 LMLTOP= specified
14 enable A20 control???
15 ???

Bitfields for 386MAX debugging flags 1:
Bit(s) Description (Table 0621)
0 DEBUG=LED
1 DEBUG=X67
2 DEBUG=INV
3 DEBUG=EMSPTED
4 DEBUG=JMP
5 DEBUG=CALL
6 DEBUG=HLT
7 DEBUG=PMR
8 DEBUG=CR3
9 DEBUG=CAPS or DEBUG=INT
10 DEBUG=RC
11 DEBUG=ROM
12 DEBUG=XM
13 DEBUG=SOR
14 DEBUG=XR
15 DEBUG=EMSERR (generate INT 01 on returning error from EMS call)

Bitfields for 386MAX debugging flags 2:
Bit(s) Description (Table 0622)
0 DEBUG=ROMSWAP
1 DEBUG=UNSHADOWROM
2 DEBUG=COMPROM
3 DEBUG=DPMIPHYS
4 DEBUG=ALLROM
5 DEBUG=VMS
6 DEBUG=XMS (generate INT 01 on XMS calls)
7 DEBUG=I06
8 DEBUG=VCPI
9 DEBUG=XDMA
10 DEBUG=X09
13 DEBUG=I67 (generate INT 01 on every INT 67 call)
14 DEBUG=EVM (generate INT 01 on entering V86 mode)
15 DEBUG=EMSSAVE or DEBUG=VDS

Bitfields for 386MAX debugging flags 3:
Bit(s) Description (Table 0623)
10 DEBUG=EPM
12 DEBUG=ABIOS
13 DEBUG=XMSPTED
14 DEBUG=TIME
15 DEBUG=SCRUB

Bitfields for 386MAX feature flags 1:
Bit(s) Description (Table 0624)
1 Weitek present
2 no DPMI services
3 NODMA
4 TERSE
5 NOROM
6 NOPARITY
8 NOFLEX (IGNOREFLEXFRAME)
11 don't create UMBs
12 don't backfill below video memory (NOLOW)
13 FRAME= specified
14 EXT= specified
15 NOEMS, allow prior expanded memory manager to provide EMS

Bitfields for 386MAX feature flags 2:
Bit(s) Description (Table 0625)
0 UNSHIFT specified (FORCEA20 disabled)
1 NOXRAM
2 NOSCSI specified
3 SCREEN specified
4 enabled EISADMA
5 slow DMA
6 RESETKEYB specified
7 ???
9 TOP384
10 ???
11 NOWARMBOOT
12 USE= specified
13 ROM= specified

Bitfields for 386MAX feature flags 3:
Bit(s) Description (Table 0626)
0 Windows3 support enabled
1 SHADOWROM
2 don't compress ROM (NOCOMPROM)
3 ??? (related to PRGREG=)
4 ??? (related to PRGREG=)
5 SHADOWRAM
6 DOS4 specified
7 NOLOADHIGH
8 NOPULSE
11 FORCEA20
12 DMA buffer enabled
13 NOSCRUB
15 NOFRAME

Bitfields for 386MAX machine type:
Bit(s) Description (Table 0627)
12 Amstrad
13 Epson
14 Zenith Data Systems
15 "ASEM"
16 NEC
17 "HPRS" model codes 69h and 6Ah
18 Dell
19 "CA"
20 ITT (Xtra Business Systems/Alcatel)
21 Toshiba 5100
22 Olivetti
23 Quadram Quad386 (BIOS model FEh, submodel A6h)
24 Tandy???
25 AST 386
26 INBOARD, ??? version
27 INBOARD, ??? version
28 INBOARD, ??? version
29 "HPRS"
30 Compaq 386
31 JET386

Format of 386MAX control block:
Offset Size Description (Table 0628)
00h WORD segment of next block (FFFFh if last)
02h WORD segment of previous block (FFFFh if first)
04h 12 BYTEs filename
10h WORD resident size in paragraphs
12h WORD environment size???
14h WORD real prsent environment size + 1 (0000h if ENVSAVE used)
16h 2 BYTEs ???
18h DWORD initial size or SIZE=n in 386LOAD commandline
1Ch DWORD SIZE=-1 ???
20h DWORD SIZE= ???
24h BYTE PRGREG= if specified, else FFh
25h BYTE ENVREG= if specified, else FFh
26h BYTE FlexFrame (00h not present, 01h present)
27h 3 BYTEs ???
2Ah BYTE GROUP= or 00h if not present
2Bh BYTE ???
2Ch WORD PSP

Format of 386MAX high memory info record:
Offset Size Description (Table 0629)
00h WORD segment address of memory region
02h WORD size of memory region in paragraphs
04h BYTE type or flags???
00h if locked out
02h if EMS page frame
04h if high RAM
42h if ROM
05h BYTE ???

Format of 386MAX ROM shadowing record:
Offset Size Description (Table 0630)
00h WORD logical start segment of ROM??? (may be used by BlueMAX when it
squeezes together the ROMs to make room)
02h WORD physical start segment of ROM
04h 2 BYTEs ???
06h WORD size of shadowed ROM in paragraphs
08h 2 BYTEs ???
0Ah WORD flags
bit 15: shadowing enabled for this ROM???
bit 14: ???
bit 13: ???
bit 12: ???
bit 10: ???

(Table 0631)
Values for 386MAX memory type:
00h unused by EMS
01h DOS
04h page frame overlapping ROM???
80h high memory
84h page frame???
87h video ROM???
Note: the type may be 00h (unused) if the 16K page is split among different
uses (such as ROM and high RAM)

(Table 0632)
Call 386MAX API (via OUT DX,AL) with:
STACK: WORD value for DX
AH = 00h unused
Return: AH = 84h (unsupported function)
AH = 01h get high memory information
ES:DI -> buffer for array of high memory info records
(see #0629)
Return: CX = number of records placed in buffer
AH = 02h get shadowed ROM info
ES:DI -> buffer for array of ROM shadowing records (see #0630)
Return: CX = number of records placed in buffer
AH = 03h get 386MAX state
ES:DI -> 90-byte buffer for state (see #0618)
Return: AH = 00h (successful)
buffer filled
AH = 04h get memory types???
ES:DI -> buffer for memory type info (array of bytes, one per
16K page) (see #0631)
Return: CX = number of bytes placed in buffer
AH = 05h get page table entries
AL = A20 control (00h enable A20 first, 01h leave unchanged)
CX = buffer size in bytes (0000h = enough for all memory from
given start to end of memory managed by 386MAX)
SI = first K to report (rounded down to 4K page)
ES:DI -> buffer for returned page table entries
Return: CX = number of bytes returned (four per 4K page)
ES:DI buffer filled
AH = 06h get memory speed info
ES:DI -> buffer for memory speed records (see #0633)
Return: AH = 00h (successful)
CX = number of bytes placed in buffer
Note: this function can take over a second to execute
AH = 07h map/unmap multiple handle pages
DX = EMS handle (on stack)
STACK: DWORD -> EMS mapping record
Return: AH = status (00h,80h,83h,8Ah,8Bh)
Format of EMS mapping record:
Offset Size Description
00h WORD function
0000h use physical page numbers
0001h use segment addresses
02h WORD EMS handle
04h WORD number of mapping entries following
06h 2N WORDs logical page number and physical page/segment
logical page FFFFh means unmap physical page
SeeAlso: INT 67/AH=50h
AH = 08h "EMM2_GOREAL" check whether possible to disable 386MAX
AL = ??? (00h or nonzero)
Return: AH = status (00h OK, A4h not possible at this time)
Note: if AL=00h, this function always returns success
AH = 09h toggle Bit Flags 1 flags
BX = bitmask of bit flags 1's flags to toggle (see #0619)
Return: AH = 00h (successful)
Note: enables A20 first
AH = 0Ah toggle Debugging Flags 1 flags
BX = bitmask of Debugging Flags 1's bits to toggle (see #0621)
Return: AH = 00h (successful)
Notes: enables A20 first
does ??? if bit 3 on after specified bits are toggled
AH = 0Bh toggle Debugging Flags 2 flags
BX = bitmask of Debugging Flags 2's bits to toggle (see #0622)
Return: AH = 00h (successful)
Note: enables A20 first
AH = 0Ch toggle feature flags 3
BX = bitmask of feature flags 3's bits to toggle (see #0626)
Return: AH = 00h (successful)
Note: enables A20 first
AH = 0Dh specify 386MAX high-memory location
BX = segment address of high-memory real-mode portion of 386MAX
CX = current segment of real-mode stub???
Return: AH = status (00h successful)
???
AH = 0Eh CRT controller register virtualization
AL = subfunction
00h allow access to CRTC I/O ports 03B4h/03B5h, 03D4h/03D5h
01h trap accesses to CRTC I/O ports
AH = 0Fh reboot system
Return: never
AH = 10h unused
Return: AH = 84h (unsupported function)
AH = 11h get high memory information
ES:DI -> 96-byte buffer for high memory info
Return: AH = 00h (successful)
ES:DI buffer filled
Notes: each byte in buffer contains bit flags for a 4K page in
the A000h-FFFFh region
bit 0: page is writeable
bit 1: physical address same as linear address
bit 2: EMS page frame
bit 6: page is part of the QPMS window
this function can take over a second to execute,
because it does a 128K read for each page in an
attempt to flush any RAM cache the system may have
AH = 12h shadow RAM mapping
AL = subfunction
00h unshadow ROMs (except page FFh if NOWARMBOOT set)
01h map shadow RAM into ROM regions???
Return: AH = 00h (successful) if AL=00h or 01h
AH = 8Fh otherwise
AH = 13h shadow RAM page protection
AL = subfunction
00h set all shadowed ROM 4K pages to read-only
01h set all shadowed ROM 4K pages to read-write
Return: AH = 00h (successful) if AL=00h or 01h
AH = 8Fh otherwise
AH = 14h get Programmable Option Select info???
ES:DI -> 54-byte buffer for POS data???
Return: AH = 00h if successful
AH = A4h on error
Note: the buffer consists of nine 6-byte fields; the first
eight for slots 1-8, the last for the system board
AH = 15h ???
???
Return: ???
AH = 16h get 386MAX memory usage screen
ES:DI -> buffer for memory info display
CX = size of buffer in bytes
Return: ES:DI buffer filled with '$'-terminated string (if
large enough to hold entire usage screen)
Note: the screen is 0303h bytes in v7.00
AH = 17h Windows 3 startup/termination
AL = subfunction
00h Windows3 initializing
DX (on stack) = Windows startup flags
DI = Windows version number (major in upper byte)
ES:BX = 0000h:0000h
DS:SI = 0000h:0000h
Return: CX = 0000h if OK for Windows to load
<> 0 if Windows should not load
ES:BX -> startup info structure
DS:SI -> Virtual86 mode enable/disable callback
01h Windows3 terminating
ES:BX -> ???
DX (on stack) = Windows exit flags
Return: ???
AH = 18h QPMS (Qualitas Protected Memory Services)
AL = subfunction
00h get QPMS configuration
Return: BX = starting segment of QPMS memory window
CX = number of 4K pages reserved for QPMS???
DX = number of 4K pages in QPMS window???
01h map QPMS memory page???
BX = 4K page number within memory reserved for QPMS???
CL = 4K page number within QPMS memory window???
02h mark all QPMS memory read-only
03h mark all QPMS memory read-write
Return: AH = status (00h,8Ah,8Bh,8Fh)
AH = 19h get linear address for physical address
EDX = physical address (low word on stack)
Return: AH = status
00h successful
EDX = linear address at which physical address
may be accessed
8Bh physical address currently not addressable
Note: enables A20 first
AH = 1Ah set page table entry
EDX = new page table entry (low word on stack)
ESI = linear address of page to map (bits 0-11 clear)
Return: AH = status (00h,8Bh)
Note: enables A20 first
AH = 1Bh get ???
Return: AH = status
BX = ???
CX = number of ???
EDX = physical address of ???
AH = 1Ch get original interrupt vector
AL = interrupt vector (00h-7Fh)
Return: AH = 00h (successful)
EDX = original vector before 386MAX loaded (segment in
high word, offset in low word)
Note: no range checking is performed; requests for INTs 80h-
FFh will return random values
AH = 1Dh display string???
SI = ???
Return: AH = 00h (successful)
???
Note: this function appears to be broken in v7.00
AH = 1Eh get memory info
ES:DI -> memory info (see #0634)
Return: ???
AH = 1Fh get DPMI host information
Return: AX = 0000h if successful
BX = DPMI flags (see #1689 at INT 31/AX=0400h)
CL = CPU type (02h = 80286, 03h = 80386, etc.)
DX = DPMI ver supported (DH=major, DL=2-digit minor)
SI = ???
ES???:DI -> ???
Note: NOP if NODPMI switch specified
AH = 20h (v7.00) get ???
AL = index of ???
Return: EDX = ??? for specified ???
AH = 21h (v7.00) STACKS support
AL = 00h get STACKS parameters
Return: BX = ??? (0060h for v7.00)
CX = number of stacks for hardware interrupts
DX = size of each stack in bytes
SI = ??? (low and high bytes are separate values)
DI = ??? (low and high bytes are separate values)
low byte = logical page number set by subfn 02h
ES = ???
AL = 01h set ??? "EMM2_DSTKS"
EBX = ???
ECX = ???
AL = 02h set ???
BL = logical page number for ??? (00h-03h)
Return: AH = status (00h,8Ah)
AH = 22h (v7.00) call ??? for every load module
AL = which function to call
00h call ???
else call ????
Return: AH = 00h
Note: if AL=00h, calls the protected-mode function pointed at by
the DWORD at offset 22h from the start of each module installed
by a LOAD= directive; if AL<>00h, it calls the function
pointed at by the DWORD at offset 28h of the load module
AH = 23h (v7.00) ???
AL = 00h set ???
BL = ???
Return: AH = 00h or unchanged (depending on ???)
AL = 01h set ???
BL = ???
BH = ???
CX = ???
DX = ??? (on top of stack)
Return: AH = status (00h if successful, 8Fh once table full)
Note: this call adds one entry to an internal table on each
call, until the table is full
AL = 02h get ???
CX = size of buffer
ES:DI -> buffer for ??? (60 bytes total data)
Return: CX = number of bytes actually returned
Note: returns the array storing the values set with AX=2301h
Format of one entry in array:
Offset Size Description
00h BYTE ??? (BL from subfn 01h)
01h WORD ??? (CX from subfn 01h)
03h BYTE ??? (BH from subfn 01h)
04h WORD ??? (DX from subfn 01h)
AL = 03h set ??? name/path
ES:DI -> buffer containing ASCIZ ???
AL = 04h get ???
ES:DI -> buffer for ASCIZ ???
Note: the ASCIZ string for subfunctions 03h and 04h does not appear
to be used by 386MAX, and may serve merely for communication
between two other Qualitas programs
AH = 24h (v7.00) high memory control
AL = 00h get high memory state
Return: BX = current state
00h high memory removed from DOS memory chain
01h high memory included in DOS memory chain
AL = 01h set high memory state
BX = new state
00h high memory removed from DOS memory chain
01h high memory included in DOS memory chain
else
Return: ??? (error, but return varies according to ???)
AH = 25h (v7.00) remove high RAM from DOS memory chain
AH = 26h (v7.00) ???
BX = ???
CX = ???
SI = ???
DI = ???
Return: AH = status
BX = ???
CX = ???
AH = 27h (v7.00) ???
AL = 00h get ???
Return: BX = number of paragraphs for ???
AL = 01h ???
BX = ???
ES??? = ???
AL = 02h ???
???
AL = 03h ???
CX = ???
DX = ???
ES??? = ???
Return: ???
AH = 28h (v7.00) get ???
Return: AH = status (00h,8Fh) (see #2089 at INT 67/AH=40h)
if AH=00h,
CX = ???
DX = ???
AH = 29h (v7.00) get ???
Return: AX = ???
AH = 40h-5Dh EMS services (see INT 67/AH=40h etc)
AH = DEh VCPI services (see INT 67/AX=DE00h etc)
Return: AH = status (as for EMS INT 67 calls)
00h successful
80h internal error
81h hardware malfunction
83h invalid handle
84h undefined function
8Ah invalid logical page nuber
8Bh illegal physical page number
8Fh undefined subfunction
A4h access denied
etc.
STACK popped (value placed in DX if no specific return value for DX)

Format of 386MAX memory speed record:
Offset Size Description (Table 0633)
00h DWORD page table entry for 4K page
04h WORD number of microticks (840ns units) required for REP LODSD of
entire 4K page

Format of 386MAX memory info [array]:
Offset Size Description (Table 0634)
00h DWORD linear start address
04h DWORD size in bytes
08h WORD XMS handle (if next byte = 04h)
??? (if next byte = 05h)
??? (if next byte = 06h)
??? (if next byte = 13h)
??? (if next byte = 14h)
??? (if next byte = 15h)
??? (if next byte = 23h)
??? (if next byte = 24h)
??? (if next byte = 26h)
else unused
0Ah BYTE type
00h = ???, 01h = VDISK,
02h = INT 15h extended memory, 03h = ??? extended,
04h = XMS handle's memory, 05h = ???, 06h = ???, 07h = ???,
08h = ???, 09h = ???, 0Ah = ???, 0Bh = ???,
11h = ???, 12h = ???, 14h = ???, 15h = ???,
19h = ???, 1Ah = ???, 1Bh = ???,
1Ch = ???, 1Dh = ???, 1Eh = ???, 1Fh = ???,
20h = ???, 21h = ???, 23h = ???, 24h = ???,

26h = ???
0Bh BYTE ??? (00h for types 00h-03h, 07h-0Bh, 19h-21h;
80h for types 04h/13h-15h/23h-26h;
??? for type 05h)
--------V-214402-----------------------------
INT 21 - PGS1600.DEV - IOCTL - GET CONFIGURATION INFO
AX = 4402h
BX = file handle for device "PGS1600$"
CX = 0018h (size of buffer)
DS:DX -> configuration buffer (see #0635)
Return: CF clear if successful
buffer filled
AX = number of bytes actually copied
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
display adapter, which provides a 1600x1200 monochrome display as
well as one of two emulations, MDA or CGA.
SeeAlso: AX=4403h"PGS1600"

Format of PGS1600.DEV configuration information:
Offset Size Description (Table 0635)
00h WORD version (high byte = major, low byte = minor)
02h WORD board initialisation mode
04h WORD board I/O address
03D0h CGA emulation
03B0h MDA emulation
0390h no emulation
0350h no emulation, alternate
06h WORD emulation buffer segment
B800h CGA emulation
B000h MDA emulation
0000h no emulation
08h WORD PG1600 graphics buffer segment
0Ah WORD number of bytes between consecutive graphic rows
0Ch WORD horizontal pixel size
0Eh WORD vertical pixel size
10h WORD horizontal dots per inch
12h WORD vertical dots per inch
14h WORD graphics buffer bits per pixel
16h WORD monitor bits per pixel
--------N-214402-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
AX = 4402h
BX = file handle referencing device "$IPCUST"
CX, DS:DX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: there are a total of 378h bytes of configuration data for IPCUST.SYS
version 2.05. If less than the entire data is read or written,
the next read/write continues where the previous one ended; this
call and AX=4403h both reset the location at which the next
operation starts to zero
v2.1+ uses a new configuration method, but allows the installation
of IPCUST.SYS for backward compatibility with other software which
must read the PC/TCP configuration
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4403h"IPCUST"
--------N-214402-----------------------------
INT 21 - WORKGRP.SYS - GET API ENTRY POINT
AX = 4402h
BX = file handle for device "NET$HLP$"
CX = 0008h
DS:DX -> buffer for entry point record
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code
Program: WORKGRP.SYS is the portion of Microsoft's Workgroup Connection which
permits communication with PCs running Windows for Workgroups or
LAN Manager
SeeAlso: AH=3Fh"WORKGRP.SYS"

Format of WORKGRP.SYS entry point record:
Offset Size Description (Table 0636)
00h WORD 3633h \ signature???
02h WORD EF6Fh /
04h DWORD address of entry point
Note: first four bytes of buffer must be 6Fh E9h 33h 36h on entry when using
IOCTL rather than READ to get the entry point record

(Table 0637)
Call WORKGRP entry point with:
STACK: WORD function number (0000h-0009h)
Return: STACK unchanged

(Table 0638)
Call WORKGRP function 00h with:
STACK: WORD 0000h (function "get ???")
Return: DX:AX -> data table

(Table 0639)
Call WORKGRP function 01h with:
STACK: WORD 0001h (function "hook ???")
Return: STACK: DWORD pointer to ???
WORD 0001h (function number)

(Table 0640)
Call WORKGRP function 02h with:
STACK: WORD 0002h (function "unhook ???")
???
Return: ???

(Table 0641)
Call WORKGRP function 03h with:
STACK: WORD 0003h (function "reenable printer port")
WORD LPT port number
Return: ???

(Table 0642)
Call WORKGRP function 04h with:
STACK: WORD 0004h (function "disable printer port")
WORD LPT port number
Return: ???

(Table 0643)
Call WORKGRP function 05h with:
STACK: WORD 0005h (function "???")
???
Return: ???

(Table 0644)
Call WORKGRP function 06h with:
STACK: WORD 0006h (function "???")
Return: STACK unchanged
AX = 0000h
DX = 0000h

(Table 0645)
Call WORKGRP functions 07h-09h with:
STACK: WORD 0007h-0009h (NOP functions)
Return: STACK unchanged
AX = 0001h
DX = 0000h
--------N-214402-----------------------------
INT 21 - 10NET v5.0 - 10BEUI.DOS - API
AX = 4402h
BX = file handle referencing device "10BEUI$"
DS:DX -> parameter record (see #0646)
CX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h"10MEMMGR",INT 6F/AH=00h"10NET"

Format of 10NET 10BEUI.DOS parameter record:
Offset Size Description (Table 0646)
00h WORD 000Ah (function number???)
02h WORD ???
04h DWORD pointer to buffer for ???
08h 4 BYTEs ???
0Ch WORD transfer size
--------N-214402-----------------------------
INT 21 - 10NET v5.0 - 10MEMMGR.SYS - API
AX = 4402h
BX = file handle referencing device "MEMMGR0$"
DS:DX -> 6-byte buffer for interface info (see #0647)
CX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h"10BEUI",INT 6F/AH=00h"10NET"

Format of 10NET 10MEMMGR.SYS interface info:
Offset Size Description (Table 0647)
00h DWORD address of entry point (see #0648)
04h WORD version (0500h for v5.00)

(Table 0648)
Call 10NET 10MEMMGR.SYS entry point with:
AL = 01h ???
BX = ???
Return: CF clear if successful
CF set on error
AX = error code
AL = 02h ???
???
AL = 03h ???
???
AL = 04h set/restore memory allocation strategy
BX = subfunction
0000h set strategy
0001h restore strategy
Return: CF clear if successful
CF set on error (if function disabled)
various registers destroyed
AL = other
Return: CF set
AX = 0000h
BL = 01h
--------V-214402-----------------------------
INT 21 - Compaq AG1024.SYS - RGDI - GET DRIVER LOCATION
AX = 4402h
BX = file handle for device "$$$$RGDI"
CX = 0006h (size of returned data)
DS:DX -> location record (see #0649)
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4403h"RGDI"

Format of Compaq AG1024.SYS location record:
Offset Size Description (Table 0649)
00h WORD signature 55AAh
02h WORD segment of ???
04h WORD segment of device driver's code
--------N-214402-----------------------------
INT 21 - FTPSOFT.DOS v3.1 - GET ???
AX = 4402h
BX = file handle for device "FTPSOFT$"
CX = size of buffer
DS:DX -> buffer for data (see #0650)
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: FTPSOFT.DOS is a device driver for Protocol Manager support from
FTP Software, Inc.
SeeAlso: AH=3Fh"PC/TCP",AX=4402h"NDIS"

Format of FTPSOFT.DOS data:
Offset Size Description (Table 0650)
00h WORD (call) BA98h (if different, no data returned)
02h DWORD -> NDIS common characteristics table
(see #0589 at AX=4402h"NDIS")
06h DWORD (call) -> new dispatch table (see #0591 at AX=4402h"NDIS")
0Ah DWORD -> 28-byte buffer for ??? data
0Eh DWORD ???
12h DWORD -> FAR function to reset dispatch jump table to defaults
16h BYTE ???
Note: the addresses in the new dispatch table are copied into an internal
jump table which may be reset by calling the function pointed at by
offset 12h
--------n-214402-----------------------------
INT 21 U - PenDOS PENDEV.SYS - GET ENTRY POINTS
AX = 4402h
BX = file handle for device "$$PENDOS" or "$$PD_REG"
CX = size of buffer (4 for $$PENDOS and a 4,8,12, or 16 for $$PD_REG)
DS:DX -> buffer for entry point record (see #0651)
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: A limited version of PenDOS by Communication Intelligence Corporation,
which provides pen capability to keyboard-based programs, is bundled
with IBM DOS 6.1
SeeAlso: AX=4403h"PENDEV.SYS"

Format of PENDEV.SYS entry point record:
Offset Size Description (Table 0651)
00h DWORD -> array of jumps
04h WORD offset of function to retrieve entry point (see #0652)
06h 2 BYTEs signature "Pe"
08h WORD offset of function to set entry point (see #0653)
0Ah 2 BYTEs signature "nD"
0Ch WORD offset of function to clear entry point (see #0654)
0Eh WORD signature "OS"

(Table 0652)
Call PENDEV.SYS function to retrieve entry point with:
AX = index of entry point (0-9)
Return: CF clear if successful
DX:AX -> desired entry point
CF set on error (AX out of range)

(Table 0653)
Call PENDEV.SYS function to set entry point with:
AX = index of entry point (0-9)
DX:SI -> new handler
Return: CF clear if successful
CF set on error (AX out of range)

(Table 0654)
Call PENDEV.SYS function to clear entry point with:
AX = index of entry point (0-9)
Return: CF clear if successful
CF set on error (AX out of range)
Note: resets the jump at the specified entry point to its default target,
which simply returns
--------N-214402-----------------------------
INT 21 U - LAN Manager - TCPDRV.DOS - API
AX = 4402h
BX = file handle referencing device "TCPDRV$"
CX = 0019h
DS:DX -> buffer containing request block
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: TCPDRV.DOS is the low-level device driver supporting LAN Manager's
TCP/IP protocol stack

Format of TCPDRV.DOS request block:
Offset Size Description (Table 0655)
00h BYTE (call) function number
00h initialize ???
06h get ???
07h get ???
01h BYTE (call) 00h
(return) error code if error, unchanged if successful
02h WORD signature 4354h ('CT')
---function 00h---
04h DWORD (call) pointer to ??? FAR function
function is called with ES:BX -> device driver request used to
invoke this function
08h 4 BYTEs ???
0Ch DWORD (call) pointer to ??? record, WORD at offset 22h is read
10h DWORD (return) -> ??? buffer if 0000h:0000h on call
---function 06h---
04h 4 BYTEs ???
08h DWORD (return) pointer to ???
---function 07h---
04h DWORD (return) pointer to ??? record
--------y-214402-----------------------------
INT 21 U - PC Tools 9 CPRLOW.EXE - GET CODE AND DATA ADDRESSES
AX = 4402h
BX = file handle referencing device "RECLOWLD"
DS:DX -> buffer for address list (see #0656)
CX ignored
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)

Format of CPRLOW address list:
Offset Size Description (Table 0656)
00h WORD segment of CPRLOW code
02h WORD offset in code segment of ??? entry point
(switches into protected mode)
04h WORD offset in code segment of jump array (see #0657)
06h WORD segment of copy of interrupt vector table at CPRLOW load time
Note: neither the entry point nor the jump array is valid until after a
CPR /LOAD, because CPR.EXE installs the code into CPRLOW at runtime.

Format of CPRLOW jump array:
Offset Size Description (Table 0657)
00h 3 BYTEs initialize CPRLOW interrupt hooks
03h 3 BYTEs reset timers and enable CPR (hotkey enable)
06h 3 BYTEs disable CPR (hotkey disable)
09h 3 BYTEs clear ??? flag, hotkey disable, and ???
0Ch 3 BYTEs initialize delay loop counter (destroys AX,BX,CX,DX)
0Fh 3 BYTEs disable CPR completely (commandline /DISABLE)
12h 3 BYTEs enable ??? if CPR enabled by both cmdline and hotkey
15h 3 BYTEs enable CPR (commandline /ENABLE)
--------m-214402-----------------------------
INT 21 U - Novell DOS 7 EMM386.EXE - GET STATE RECORD???
AX = 4402h
BX = file handle for device "EMMXXXX0"
CX = 003Eh (size of state record)
DS:DX -> buffer for state record (see #0658)
Return: CF clear if successful
buffer filled (see #2044 at INT 67/AH=3Fh)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)

Format of Novell DOS 7 EMM386.EXE state record:
Offset Size Description (Table 0658)
00h WORD signature EDC0h
02h 60 BYTEs ???
--------m-214402SF00-------------------------
INT 21 U - Memory Managers - GET API ENTRY POINT
AX = 4402h subfn 00h
BX = file handle for device "EMMXXXX0"
CX = 0006h (size of buffer in bytes)
DS:DX -> buffer for API entry point record (see #0660)
first byte must be 00h on entry
Return: CF clear if successful
buffer filled (see #2044 at INT 67/AH=3Fh)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: this function is supported by Microsoft EMM386.EXE v4.45+ and
CEMM v5.10+, and is intended for use by MS Windows as it starts up
if no other program has hooked INT 67, an alternate installation
check for CEMM is testing for the string
"COMPAQ EXPANDED MEMORY MANAGER 386" at offset 14h in the INT 67
handler's segment; if present, the word at offset 12h contains the
offset of the API entry point
SeeAlso: AX=4402h/SF=01h,AX=4402h/SF=02h,AX=4402h"EMM386",INT 67/AH=3Fh

Format of memory manager API entry point record:
Offset Size Description (Table 0659)
00h WORD ??? (0022h for CEMM 5.11, 0025h for MS EMM386 v4.45)
02h DWORD manager's private API entry point
(see #0660,#2107 at INT 67/AX=FFA5h)

(Table 0660)
Call CEMM v5.10+ entry point with:
AH = 00h get memory manager's state
Return: AH = state
bit 0: turned OFF
bit 1: AUTO mode enabled
AH = 01h set memory manager's state
AL = new state (00h ON, 01h OFF, 02h AUTO)
Return: CF clear if successful
CF set on error
AH = 02h Weitek coprocessor support
AL = subfunction
00h get Weitek support state
Return: AL = status
bit 0: Weitek coprocessor is present
bit 1: Weitek support is enabled
01h turn on Weitek support
02h turn off Weitek support
Return: CF clear if successful
CF set on error
AH = error code (01h invalid subfunc, 02h no Weitek)
AH = 05h get statistics
???
AH > 06h
Return: CF set
AH = 01h (invalid function)
Notes: AH=03h,04h,06h are NOPs which return CF clear, presumably for backwards
compatibility with earlier versions of CEMM
in v5.11, AH=05h merely prints an error message (using INT 21/AH=09h)
stating that a different version of CEMM is installed and it is
therefore not possible to display the statistics
--------m-214402SF01-------------------------
INT 21 U - Memory Managers - GET EMM IMPORT STRUCTURE ADDRESS
AX = 4402h subfn 01h
BX = file handle for device "EMMXXXX0"
CX = 0006h (size of buffer in bytes)
DS:DX -> buffer for EMM import structure record (see #0661)
first byte must be 01h on entry
Return: CF clear if successful
buffer filled (see also #2044 at INT 67/AH=3Fh)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: this function is supported by Microsoft EMM386.EXE v4.45+,
QEMM-386 v6+, and CEMM v5.10+, and is intended for use by MS Windows
as it starts up
for QEMM-386, this call always returns an error if Windows3 support
has been disabled with the NW3 switch
SeeAlso: AX=4402h/SF=00h,AX=4402h"EMM386",INT 2F/AX=D201h/BX=5145h
SeeAlso: INT 67/AH=3Fh

Format of EMM import structure record:
Offset Size Description (Table 0661)
00h DWORD physical address of EMM import structure (see #0662)
04h BYTE EMM import structure major version
05h BYTE EMM import structure minor version
Note: version 1.00 contains only EMS information (Windows 3.0+)
version 1.10 contains UMB/XMS/HMA/EMS information (Windows 3.1)
version 1.11 is version 1.10 plus memory manager maker/product name
SeeAlso: #2084

Format of Global EMM Import record:
Offset Size Description (Table 0662)
00h BYTE bit flags
bit 2: ???
bit 3: free EMM386 virtual HMA only if hma_page_table_paddr!=0
bit 4: no UMB???
01h BYTE reserved (0)
02h WORD size of structure in bytes
04h WORD structure version
06h DWORD reserved
0Ah 384 BYTEs 64 EMS frame status records (see #0663), one per 16K of
real-mode 1M address space
18Ah BYTE ??? (must be at least 3*number_of_EMS_frames+4)
18Bh BYTE number of UMB frame descriptors following
18Ch 4N DWORDs UMB frame descriptors
each is 4 DWORDs giving physical page numbers for the four
4K pages of a 16K EMS frame (00000000h if non-UMB page)
var BYTE number of EMS handle info records following
16N BYTEs EMS handle info records (see #0665)
---version 1.10+ ---
DWORD realmode INT 67 vector (used by Windows to set breakpoints)
DWORD physical address of HMA page table values
BYTE number of free page entries following
2N DWORDs free page entries
each is:
DWORD physical page number
DWORD number of consecutive physical pages
BYTE number of XMS handle info records following
00h if memory manager does not emulate XMS or has real mode
XMS code which can execute in the Windows environment
12N BYTEs XMS handle info records (see #0666)
BYTE number of free UMB info records following
2N WORDs free UMB info records
each is:
WORD real mode start segment
WORD size in paragraphs
---version 1.11---
20 BYTEs blank-padded maker name
20 BYTEs blank-padded product name

Format of EMS frame status record:
Offset Size Description (Table 0663)
00h BYTE frame type (see #0664)
01h BYTE owner handle (00h/FFh = none) from frame including UMB
index to UMB frame descriptors
02h WORD logical page for frame, 7FFFh if none, FFFFh if non-EMS frame
04h BYTE EMS physical page number (FFh for non-EMS = don't care???)
05h BYTE flags for non-EMS frames (00h for EMS frame)
bits 0,1 for first 4K, bits 2,3 for second 4K, etc:
10: direct mapping (linear address = physical address)
01: UMB mapping

Bitfields for EMS frame type:
Bit(s) Description (Table 0664)
0 EMS frame
1 (if EMS frame) in standard 64K page frame
2 first 4K of frame is UMB
3 second 4K of frame is UMB
4 third 4K of frame is UMB
5 last 4K of frame is UMB

Format of EMS handle info record:
Offset Size Description (Table 0665)
00h BYTE handle number (00h = system handle)
01h BYTE flags
bit 0: normal handle rather than system handle
bit 2: ??? (set by some EMS managers)
02h 8 BYTEs EMS handle's name
0Ah WORD number of 16K pages for handle
0Ch DWORD physical address of page table entries forming page map
Note: all values should be zero for the system handle if no large frame
support is present

Format of XMS handle info record:
Offset Size Description (Table 0666)
00h WORD handle
02h WORD flags
bit 0: handle usable by Windows
(already in use when Windows started if clear)
bit 1: reserved (0)
04h DWORD size in KB (may be zero, used only if flags bit 0 set)
08h DWORD physical address (only if flags bit 0 set)
--------m-214402SF02-------------------------
INT 21 U - Memory Managers - GET MEMORY MANAGER VERSION
AX = 4402h subfn 02h
BX = file handle for device "EMMXXXX0"
CX = 0002h (size of buffer in bytes)
DS:DX -> buffer for memory manager version (see #0667)
first byte must be 02h on entry
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: this function is supported by Microsoft EMM386.EXE v4.45+ and
CEMM v5.10+, and is intended for use by MS Windows as it starts up
SeeAlso: AX=4402h/SF=00h,AX=4402h"EMM386",INT 67/AH=3Fh

Format of memory manager version:
Offset Size Description (Table 0667)
00h BYTE major version
01h BYTE minor version (binary)
--------m-214402-----------------------------
INT 21 U - Microsoft EMM386.EXE v4.45 - GET MEMORY MANAGER INFORMATION
AX = 4402h
BX = file handle for device "EMMXXXX0"
CX = size of buffer in bytes (varies, see below)
DS:DX -> buffer for returned data (see #0668)
first byte must be set on entry to indicate desired data
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: an error is returned if the number of bytes to be read does not match
the number of bytes returned for the specified data item
this function is part of the interface which allows MS Windows to
cooperate with memory managers
SeeAlso: AX=4402h/SF=00h,AX=4402h/SF=01h,AX=4402h/SF=02h,INT 67/AX=FFA5h

Format of EMM386.EXE data buffer:
Offset Size Description (Table 0668)
00h BYTE (call) function
03h get ???
04h get ???
---function 03h---
00h WORD ???
02h WORD ???
---function 04h---
00h WORD segment of UMB containing EMM386 code/data
02h WORD number of paragraphs of EMM386 code/data in UMB
04h WORD ???
----------214402-----------------------------
INT 21 U - IFSHLP.SYS - GET ENTRY POINT
AX = 4402h
BX = file handle for device "IFS$HLP$"
CX = 0008h (size of buffer in bytes)
DS:DX -> buffer for entry point record (see #0570 at AH=3Fh"IFSHLP")
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AH=3Fh"IFSHLP"
--------D-214403-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO CHARACTER DEVICE CONTROL CHANNEL
AX = 4403h
BX = file handle referencing character device
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: format of data is driver-specific (see below for some specific cases)
if the file handle refers to "4DOSSTAK", the 4DOS (v2.x-3.03)
KEYSTACK.SYS driver will push the specified characters on the
keyboard stack; similarly for "NDOSSTAK", the NDOS KEYSTACK.SYS
driver will push the characters onto the keyboard stack
SeeAlso: AX=4400h,AX=4402h,AX=4405h,INT 2F/AX=122Bh,INT 2F/AX=D44Dh
SeeAlso: INT 2F/AX=D44Fh
--------c-214403-----------------------------
INT 21 - SMARTDRV.SYS v3.x only - IOCTL - CACHE CONTROL
AX = 4403h
BX = handle for device "SMARTAAR"
CX = number of bytes to write
DS:DX -> SMARTDRV control block (see #0670)
Return: CF clear if successful
AX = number of bytes actually written
0000h if control block too small for given command
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h"SMARTDRV",INT 2F/AX=4A10h/BX=0000h

(Table 0669)
Values for SMARTDRV function code:
00h flush cache
01h flush and discard cache
02h disable caching (flushes and discards cache first)
03h enable caching
04h control write caching
05h set flushing tick count
06h lock cache contents
07h unlock cache contents
08h set flush-on-reboot flag
09h unused
0Ah control full-track caching
0Bh reduce cache size
0Ch increase cache size
0Dh set INT 13 chain address

Format of SMARTDRV control block:
Offset Size Description (Table 0670)
00h BYTE function code (see #0669)
---functions 00h-03h,06h,07h---
no additional fields
---function 04h---
01h BYTE write caching control action
00h turn off write-through
01h turn on write-through
02h turn off write buffering (also flushes cache)
03h turn on write buffering (also flushes cache)
---function 05h---
01h WORD number of timer ticks between cache flushes
---function 08h---
01h BYTE new flush-on-reboot flag (00h off, 01h on)
---function 0Ah---
01h BYTE full-track writes are
00h not cached
01h cached
---functions 0Bh,0Ch---
01h WORD number of 16K pages by which to increase/reduce cache size
---function 0Dh---
01h DWORD new address to which to chain on INT 13
Note: the previous address is not preserved
--------d-214403-----------------------------
INT 21 - CD-ROM device driver - IOCTL OUTPUT
AX = 4403h
BX = file handle referencing character device for CD-ROM driver
CX = number of bytes to write
DS:DX -> control block (see #0671)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4402h"CD-ROM",INT 2F/AX=0802h

Format of CR-ROM control block:
Offset Size Description (Table 0671)
00h BYTE function code
00h eject disk
01h lock/unlock door
02h reset drive
03h control audio channel
04h write device control string
05h close tray
---functions 00h,02h,05h---
no further fields
---function 01h---
01h BYTE lock function
00h unlock door
01h lock door
---function 03h---
01h BYTE input channel (0-3) for output channel 0
02h BYTE volume for output channel 0
03h BYTE input channel (0-3) for output channel 1
04h BYTE volume for output channel 1
05h BYTE input channel (0-3) for output channel 2
06h BYTE volume for output channel 2
07h BYTE input channel (0-3) for output channel 3
08h BYTE volume for output channel 3
Note: output channels 0 and 1 are left and right, 2 and 3 are left prime and
right prime; a volume of 00h is off
---function 04h---
01h N BYTEs bytes to send directly to the CD-ROM drive without
interpretation
--------d-214403-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
AX = 4403h
BX = handle for device "SCSITAPE"
CX = number of bytes to write
DS:DX -> SCSITAPE control block (see #0672)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4405h"ST-01",INT 78/AH=10h

Format of SCSITAPE control block:
Offset Size Description (Table 0672)
00h WORD command type
'F' Format (argument 1 = interleave, argument 2 = format type)
'E' Erase
'R' Rewind
'L' Load
'N' No Load
'S' Space (argument 1 = count, argument 2 = type)
'M' File Mark (argument 1 = count)
'A' Reassign
02h WORD argument 1
04h WORD argument 2
06h WORD segment of command buffer
08h WORD offset of command buffer
0Ah WORD length of command buffer
--------E-214403-----------------------------
INT 21 U - AI Architects - OS/x86??? - API
AX = 4403h
BX = handle for device "AIA_OS"
CX = number of bytes to write (ignored)
DS:DX -> 12-byte buffer, first byte is command:
81h installation check
82h get API entry point
84h uninstall
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Ch,0Dh) (see #0811 at AH=59h)
Notes: these functions are only available if the DOS extender was loaded as a
device driver in CONFIG.SYS
called by TKERNEL (a licensed version of AI Architects/Ergo OS/x86)
SeeAlso: INT 2F/AX=FBA1h/BX=0081h,INT 2F/AX=FBA1h/BX=0082h
Index: installation check;OS/x86|entry point;OS/x86|uninstall;OS/x86

Format of buffer on return:
Offset Size Description (Table 0673)
00h 4 BYTEs signature "IABH"
---if func 81h---
(no additional fields)
---if func 82h---
04h DWORD pointer to API entry point (see INT 2F/AX=FBA1h/BX=0082h)
---if func 84h---
04h WORD success indicator
06h WORD segment of ???
08h WORD segment of ??? memory block to free if nonzero
0Ah WORD segment of ??? memory block to free if nonzero
--------V-214403-----------------------------
INT 21 - PGS1600.DEV - IOCTL - SET CONFIGURATION???
AX = 4403h
BX = file handle for device "PGS1600$"
CX = 0018h (size of buffer)
DS:DX -> configuration buffer (see #0635 at AX=4402h"PGS1600")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
display adapter, which provides a 1600x1200 monochrome display as
well as one of two emulations, MDA or CGA.
SeeAlso: AX=4402h"PGS1600"
--------N-214403-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
AX = 4403h
BX = file handle referencing device "$IPCUST"
CX, DS:DX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Notes: there are a total of 378h bytes of configuration data for IPCUST.SYS
version 2.05. If less than the entire data is read or written,
the next read/write continues where the previous one ended; this
call and AX=4402h both reset the location at which the next
operation starts to zero
v2.1+ uses a new configuration method, but allows the installation
of IPCUST.SYS for backward compatibility with other software which
must read the PC/TCP configuration
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4402h"IPCUST"
--------V-214403-----------------------------
INT 21 - Compaq AG1024.SYS - CPQ_MGES - IOCTL OUTPUT
AX = 4403h
BX = file handle referencing device "CPQ_MGES"
DS:DX -> request packet (see #0674)
CX ignored
Return: CF clear if successful
AX destroyed
data buffer filled (if applicable)
first word of request packet set to number of bytes of data
available (amount returned is smaller of this and requested
amount)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4403h"RGDI"

Format of Compaq AG1024.SYS request packet:
Offset Size Description (Table 0674)
00h WORD function
0000h get ??? (26h bytes)
0001h get ??? (36h bytes)
0002h set ??? (same as returned by function 0001h)
0003h get ??? (6 bytes)
0004h get ???
0005h get ???
0006h get ??? (10h bytes)
0007h set ??? (same as returned by function 0006h)
---functions 00h-03h,06h,07h---
02h WORD size of data buffer
04h DWORD -> buffer for function's data
---functions 04h,05h---
02h WORD ???
04h WORD size of data buffer
06h DWORD -> buffer to receive data
--------V-214403-----------------------------
INT 21 - Compaq AG1024.SYS - RGDI - IOCTL OUTPUT
AX = 4403h
BX = file handle referencing device "$$$$RGDI"
DS:DX -> request packet (see #0675)
CX ignored
Return: CF clear if successful
AX destroyed
data buffer filled (if applicable)
first word of request packet set to number of bytes of data
available (amount returned is smaller of this and requested
amount)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4402h"RGDI",AX=4403h"CPQ_MGES"

Format of Compaq AG1024.SYS request packet:
Offset Size Description (Table 0675)
00h WORD function
0000h get entry points
0001h get ???
02h DWORD address of buffer for returned data
--------m-214403SF01-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - TURN 386MAX OFF
AX = 4403h subfn 01h
BX = handle for device "386MAX$$"
DS:DX -> BYTE 01h
CX ignored
Return: DS:DX -> BYTE status (00h = successful)
CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: this function will fail if any EMS or UMBs are in use
SeeAlso: AX=4403h/SF=02h,AX=4403h/SF=03h,AX=4403h/SF=05h
--------m-214403SF02-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - TURN 386MAX ON
AX = 4403h subfn 02h
BX = handle for device "386MAX$$"
DS:DX -> BYTE 02h
CX ignored
Return: DS:DX -> BYTE status (00h = successful)
CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4403h/SF=01h,AX=4403h/SF=03h,AX=4403h/SF=05h
--------m-214403SF03-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - SET STATE
AX = 4403h subfn 03h
BX = handle for device "386MAX$$"
CX = number of bytes to copy (up to size of state buffer)
DS:DX -> BYTE 03h followed by state buffer
(see #0618 at AX=4402h"386MAX")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: the first byte of the buffer must be either 01h, 02h, or 03h
(specifying the version of the state record) and the buffer must
contain CX bytes AFTER the initial byte
SeeAlso: AX=4402h"386MAX"
--------m-214403SF05-------------------------
INT 21 U - Qualitas 386MAX v7.00+ - LIMIT AUTOMATIC ACTIVATION TO STD EMS CALLS
AX = 4403h subfn 05h
BX = handle for device "386MAX$$"
DS:DX -> BYTE 05h
CX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Desc: specifies that 386MAX will only shift from AUTO to ON mode on standard
EMS calls INT 67/AH=40h-5Dh
SeeAlso: AX=4403h/SF=02h,AX=4403h/SF=03h,AX=4403h/SF=06h
--------m-214403SF06-------------------------
INT 21 U - Qualitas 386MAX v7.00+ - ALLOW AUTOMATIC ACTIVATION ON ANY INT 67
AX = 4403h subfn 06h
BX = handle for device "386MAX$$"
DS:DX -> BYTE 06h
CX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Desc: specified that 386MAX should shift from AUTO to ON mode on any INT 67
call other than INT 67/AH=3Fh
SeeAlso: AX=4403h/SF=01h,AX=4403h/SF=03h,AX=4403h/SF=05h
--------n-214403-----------------------------
INT 21 U - PenDOS PENDEV.SYS - ???
AX = 4403h
BX = file handle for device "$$PENDOS" or "$$PD_REG"
CX = size of buffer
DS:DX -> buffer containing ???
Return: CF clear if successful
buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: A limited version of PenDOS by Communication Intelligence Corporation,
which provides pen capability to keyboard-based programs, is bundled
with IBM DOS 6.1
Note: this call sets the WORD at offset 1Ah into the device driver request
header used to call the driver to 0000h.
SeeAlso: AX=4402h"PENDEV.SYS"
--------D-214404-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM BLOCK DEVICE CONTROL CHANNEL
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc.)
CX = number of bytes to read
DS:DX -> buffer
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: format of data is driver-specific
SeeAlso: AX=4402h,AX=4405h,INT 2F/AX=122Bh
--------k-214404-----------------------------
INT 21 - Stacker - GET DEVICE DRIVER ADDRESS AND SET VOLUME NUMBER
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc.)
CX = 0004h
DS:DX -> DWORD buffer to receive device driver address
Note: In addition to returning the address of the Stacker device driver,
this call also sets the volume number at offset 3Eh in the device
driver (see INT 25/AX=CDCDh)
SeeAlso: INT 25/AX=CDCDh
--------k-214404-----------------------------
INT 21 - Stacker - GET STACVOL FILE SECTORS
AX = 4404h
BL = drive number (0 is current drive)
CX = byte count (i.e., 200h = 1 sector)
DS:DX -> buffer (see #0676)
Return: Data Buffer contains the number of sectors requested from the
STACVOL physical file for the drive specified.

Format of Stacker buffer:
Offset Size Description (Table 0676)
00h WORD 01CDh
02h WORD sector count
04h DWORD number of starting sector
08h DWORD far pointer to Data Buffer
--------k-214404-----------------------------
INT 21 - DUBLDISK.SYS v2.6 - GET INFO
AX = 4404h
BL = drive number of DoubleDisk drive (00h = default, 01h = A:, etc.)
CX = number of bytes (000Ah-0014h, call ignored otherwise)
DS:DX -> data record (see #0677)
Return: CF clear if successful
AX = number of bytes read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: DUBLDISK.SYS is the device driver portion of DoubleDisk, a disk
expander by Vertisoft Systems, Inc.
Note: the installation check for v2.6 consists of scanning memory for the
signature "FAT 2.6 byte:", which is immediately followed by a data
table (see #0678)
BUG: VOPT (a disk optimizer by Golden Bow Software) assumes that any driver
which returns the "correct" number of bytes when the first word of
the buffer for the data record contains the signature value 4444h is
DoubleDisk; a workaround is for the non-DoubleDisk driver to return
no data if the signature is present
SeeAlso: AX=440Dh
Index: installation check;DUBLDISK.SYS

Format of DUBLDISK data record:
Offset Size Description (Table 0677)
00h WORD (call) signature 4444h
02h BYTE (call) function
00h ???
01h ???
---function 00h---
02h BYTE (return) ???
03h BYTE (return) ???
---function 01h---
02h WORD (return) 4444h
04h WORD allocation unit size???
06h WORD ???
08h WORD ???
0Ah BYTE ???

Format of DUBLDISK signature data table:
Offset Size Description (Table 0678)
00h 5 BYTEs ???
05h BYTE first drive number
06h BYTE number of drives
07h ???
--------k-214404-----------------------------
INT 21 - DBLSPACE.BIN - IOCTL - FLUSH OR INVALIDATE INTERNAL CACHES
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = 000Ah (size of DSPACKET structure)
DS:DX -> DSPACKET structure (see #0679)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4405h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DoubleSpace DSPACKET structure:
Offset Size Description (Table 0679)
00h WORD signature 444Dh ("DM")
02h BYTE command code
46h ('F') flush internal caches
49h ('I') flush and invalidate internal caches
03h WORD result code
(return) 4F4Bh ("OK") if successful, else unchanged
05h 5 BYTEs padding
--------k-214404-----------------------------
INT 21 - DBLSPACE.BIN v6.2 - IOCTL - GET ??? FOR SPECIFIED DRIVE
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = size of DSPACKET structure (ignored in DOS 6.2)
DS:DX -> DSPACKET structure (see #0680)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4405h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DoubleSpace DSPACKET structure:
Offset Size Description (Table 0680)
00h WORD signature 444Dh ("DM")
02h BYTE command code
53h ('S') get ??? for specified drive
03h WORD result code
(return) 4F4Bh ("OK") if successful, else unchanged
05h DWORD (return) pointer to 96-byte ??? data
09h DWORD (return) pointer to ??? data
0Dh 3 BYTEs reserved
--------d-214404-----------------------------
INT 21 U - xDISK v3.31 - CONFIGURE
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = 0047h (length of version string)
DS:DX -> 79-byte buffer for version string and ???
DS:0081h = commandline containing new switches for driver
Return: CF clear if successful
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: xDISK is a shareware resizeable EMS RAMdisk by FM de Monasterio
SeeAlso: AX=4405h"xDISK",INT 2F/AH=DDh/BX=7844h"xDISK"
--------c-214404-----------------------------
INT 21 - COMBI-disk v1.13 - GET DATA RECORD
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = 0032h (length of data packet)
DS:DX -> buffer for data packet (see #0681)
Return: CF clear if successful
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: COMBI-disk is a shareware combination cache and RAMdisk sharing a
single pool of memory by Vadim V. Vlasov
Note: the installation check consists of scanning the valid drives for one
which returns a correctly-sized data packet with the proper
signature in the first field
SeeAlso: AX=4405h"COMBI"
Index: installation check;COMBI-disk

Format of COMBI-disk data packet:
Offset Size Description (Table 0681)
00h 6 BYTEs ASCIZ signature "COMBI"
06h WORD version (high byte = major, low = decimal minor version)
08h BYTE current options (see below)
09h BYTE sectors per allocation block
0Ah WORD maximum buffer in KB
0Ch WORD current buffer in KB (less than max if XMS memory being lent)
0Eh WORD total number of allocation blocks
10h WORD current number of allocation blocks
12h WORD number of blocks being used by RAM disk
14h WORD number of blocks being used by cache or unused
16h WORD number of dirty cache blocks
18h WORD number of blocks which could not be written out due to errors
1Ah WORD total number of read requests
1Ch WORD total number of sectors read
1Eh WORD number of BIOS read requests (cache misses)
20h WORD number of sectors read via BIOS (cache misses)
22h WORD total number of write requests
24h WORD total number of sectors written
26h WORD number of BIOS write requests
28h WORD number of sectors written via BIOS
2Ah WORD number of RAM disk read requests
2Ch WORD number of sectors read from RAM disk
2Eh WORD number of RAM disk write requests
30h WORD number of sectors written to RAM disk
--------d-214404-----------------------------
INT 21 - SFS v1.00 - GET CONFIGURATION INFORMATION
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = 001Ah (length of data packet)
DS:DX -> buffer for data packet (see #0682)
Return: CF clear if successful
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: SFS (Secure FileSystem) is a shareware encrypting disk driver by
Peter C. Gutmann
SeeAlso: AX=4405h"SFS"

Format of SFS data packet:
Offset Size Description (Table 0682)
00h 4 BYTEs signature string "SFS1"
04h WORD SFS unit number (0-based)
06h WORD drive on which the SFS volume is mounted
08h DWORD sector offset of logical volume from start of physical volume
0 if logical volume = physical volume
0Ch WORD flag: 00h = no disk mounted, 01h = disk mounted
0Eh WORD flag: 00h read/write, 01h read-only
10h WORD quick-unmount hotkey (high byte = shift state, low = scan code)
12h WORD auto-unmount time in minutes, or 0000h if already expired, or
FFFFh if not set
14h WORD time in minutes remaining before auto-unmount
16h WORD internal driver check code
0000h no error
0001h driver consistency check failed
0002h unit consistency check failed
18h WORD disk access mode
0000h BIOS
0001h IDE direct access
0002h SCSI direct access
--------D-214405-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO BLOCK DEVICE CONTROL CHANNEL
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: format of data is driver-specific
SeeAlso: AX=4403h,AX=4404h,INT 2F/AX=122Bh
--------d-214405-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
AX = 4405h
BX = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> SCSIDISK control block (see also #0672 at AX=4403h"ST-01")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4403h"ST-01"
--------k-214405-----------------------------
INT 21 U - DBLSPACE.BIN - IOCTL - FLUSH OR INVALIDATE INTERNAL CACHES
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = 000Ah (size of DSPACKET structure)
DS:DX -> DSPACKET structure (see #0683)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: this call is identical to the documented AX=4404h
SeeAlso: AX=4404h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DoubleSpace DSPACKET structure:
Offset Size Description (Table 0683)
00h WORD signature 444Dh ("DM")
02h BYTE command code
46h ('F') flush internal caches
49h ('I') flush and invalidate internal caches
03h WORD result code
(return) 4F4Bh ("OK") if successful, else unchanged
05h 5 BYTEs padding
--------d-214405-----------------------------
INT 21 U - xDISK v3.31 - ???
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> buffer containing version string
???
Return: CF clear if successful
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: xDISK is a shareware resizeable EMS RAMdisk by FM de Monasterio
SeeAlso: AX=4404h"xDISK",INT 2F/AH=DDh/BX=7844h"xDISK"
--------d-214405-----------------------------
INT 21 - COMBI-disk v1.13 - CONTROL COMBI-disk
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc) for RAM disk
CX = number of bytes to write
DS:DX -> buffer containing command packet (see #0685)
Return: CF clear if successful
AX = number of bytes actually transferred
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
SeeAlso: AX=4404h"COMBI"

(Table 0684)
Values for COMBI-disk command code:
80h flush cache
81h change options byte
82h shrink memory
83h expand memory
84h get dirty block information
85h reset write errors
86h reset counters

Format of COMBI-disk command packet:
Offset Size Description (Table 0685)
00h WORD version
02h BYTE command code (see #0684)
---command code 80h---
no additional fields
---command code 81h---
03h BYTE new options byte (see #0686)
---command code 82h---
03h WORD number of KB to release
---command code 83h---
03h WORD number of KB to expand
---command code 84h---
03h DWORD -> buffer for block info (see #0687)
---command code 85h---
03h DWORD block ID
---command code 86h---
03h BYTE which counters to reset
bit 0: hard disk read counts
bit 1: hard disk write counts
bit 2: RAM disk read/write counts
Note: multiple commands may be placed in a single packet by stringing
together as many command/argument pairs as desired

Bitfields for COMBI-disk options byte:
Bit(s) Description (Table 0686)
0 cache off
1 cache frozen
2 write caching enabled
3 delayed writing disabled
5 fix memory allocation (no XMS lending)
6 no 'sector not found' error

Format of COMBI-disk block info:
Offset Size Description (Table 0687)
00h DWORD block ID
04h BYTE bitmask of valid sectors in block
05h BYTE bitmask of dirty sectors in block
06h BYTE last error returned by BIOS
07h BYTE number of errors
--------D-214405-----------------------------
INT 21 - SFS v1.00 - DRIVER CONTROL
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> data to write (see #0689)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Program: SFS (Secure FileSystem) is a shareware encrypting disk driver by
Peter C. Gutmann
SeeAlso: AX=4404h"SFS"

(Table 0688)
Values for SFS control function:
00h "PACKET_SET_DISKINFO" set disk parameters
01h "PACKET_SET_KEYINFO" set keying information
02h "PACKET_SET_READONLY" select read/write or read-only
03h "PACKET_SET_DRIVENO" set drive number to mount
04h "PACKET_SET_MOUNTSTATUS" set mount status
05h "PACKET_SET_UNMOUNT" set/clear quick-unmount hotkey
06h "PACKET_SET_TIMEOUT" set/clear auto-unmount timeout

Format of SFS control data packet:
Offset Size Description (Table 0689)
00h WORD signature 4330h ('C0')
02h WORD function (see #0688)
---function 00h---
04h WORD sector size in bytes
06h BYTE sectors per cluster
07h WORD number of boot sectors
09h BYTE number of copies of FAT
0Ah WORD size of root directory in entries
0Ch WORD number of sectors on disk, 16-bit
0Eh BYTE media descriptor byte
0Fh WORD sectors per FAT
11h WORD sectors per track
13h WORD number of heads
15h DWORD number of hidden sectors
19h DWORD number of sectors on disk, 32-bit
---function 01h---
04h 20 BYTEs master IV for encrypted disk
18h 64 BYTEs NDC/SHS keying information
---function 02h---
04h WORD read-only state: 00h read-only, 01h read/write
---function 03h---
04h WORD drive number (see #0690)
06h DWORD sector offset of logical volume from start of physical volume
0 if logical volume = physical volume
---function 04h---
04h WORD mount status (00h unmounted, 01h mounted)
---function 05h---
04h WORD hotkey (high byte = shift state, low byte = scan code or 00h)
0000h to disable hotkey
---function 06h---
04h WORD timeout in minutes before automatic unmount
0000h to disable auto-unmount
Notes: the data for function 00h corresponds to a DOS BPB (see AH=53h)
functions 00h, 01h, and 03h automatically unmount the encrypted drive
unmounting a drive with function 04h also destroys the encryption
information in the driver and forces all dirty buffers to be flushed

Bitfields for SFS drive number:
Bit(s) Description (Table 0690)
15-12 drive access mode
0000 BIOS access
0001 direct IDE access
0010 direct SCSI access
---if BIOS access---
11-8 unused (0)
7-0 BIOS drive number
---if IDE access---
11-8 unused (0)
7-0 IDE drive number
---if SCSI access---
11-8 SCSI host number
7-4 SCSI target ID
3-0 SCSI logical unit number
--------D-214406-----------------------------
INT 21 - DOS 2+ - IOCTL - GET INPUT STATUS
AX = 4406h
BX = file handle
Return: CF clear if successful
AL = input status
00h not ready (device) or at EOF (file)
FFh ready
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: files may not register as being at EOF if positioned there by AH=42h
SeeAlso: AX=4407h,INT 2F/AX=122Bh
--------D-214407-----------------------------
INT 21 - DOS 2+ - IOCTL - GET OUTPUT STATUS
AX = 4407h
BX = file handle
Return: CF clear if successful
AL = input status
00h not ready
FFh ready
CF set on error
AX = error code (01h,05h,06h,0Dh) (see #0811 at AH=59h)
Note: for DOS 2+, files are always ready for output, even if the disk is
full or no media is in the drive
SeeAlso: AX=4406h,INT 2F/AX=122Bh
--------D-214408-----------------------------
INT 21 - DOS 3.0+ - IOCTL - CHECK IF BLOCK DEVICE REMOVABLE
AX = 4408h
BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
AX = media type (0000h removable, 0001h fixed)
CF set on error
AX = error code (01h,0Fh) (see #0811 at AH=59h)
SeeAlso: AX=4400h,AX=4409h,INT 2F/AX=122Bh
--------D-214409-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE
AX = 4409h
BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
DX = device attribute word
bit 15: drive is SUBSTituted
bit 12: drive is remote
bit 9: direct I/O not allowed
CF set on error
AX = error code (01h,0Fh) (see #0811 at AH=59h)
Note: on local drives, DX bits not listed above are the attribute word from
the device driver header (see #0785 at AH=52h); for remote drives,
the other bits appear to be undefined for DOS versions prior to 5.0
(they are all cleared in DOS 5+)
checking whether DX=0800h on return appears to be a fairly reliable
method for detecting Microsoft's RAMDRIVE
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh
--------D-21440A-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF HANDLE IS REMOTE
AX = 440Ah
BX = handle
Return: CF clear if successful
DX = attribute word (as stored in SFT)
bit 15: set if remote
bit 14: date/time not set on close
CF set on error
AX = error code (01h,06h) (see #0811 at AH=59h)
Notes: if file is remote, Novell Advanced NetWare 2.0 returns the number of
the file server on which the handle is located in CX
DR-DOS 3.41 and 5.0 clear all bits of DX except bit 15
SeeAlso: AX=4400h,AX=4409h,AH=52h,INT 2F/AX=122Bh
--------D-21440B-----------------------------
INT 21 - DOS 3.1+ - IOCTL - SET SHARING RETRY COUNT
AX = 440Bh
CX = pause between retries (default 1)
DX = number of retries (default 3)
Return: CF clear if successful
CF set on error
AX = error code (01h) (see #0811 at AH=59h)
Notes: delay is dependent on processor speed (value in CX specifies number of
64K-iteration empty loops to execute)
if DX=0000h on entry, the retry count is left unchanged
SeeAlso: AH=52h,INT 2F/AX=1224h,INT 2F/AX=122Bh
--------D-21440C-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC CHARACTER DEVICE REQUEST
AX = 440Ch
BX = device handle
CH = category code (see #0691)
CL = function number (see #0692)
DS:DX -> parameter block (see #0693,#0694,#0695,#0696,#0697,#0698)
SI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)
DI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
DS:DX -> iteration count if CL=65h
SI = returned value (European MS-DOS 4.0, OS/2 comp box)
DI = returned value (European MS-DOS 4.0, OS/2 comp box)
Note: DR-DOS 3.41 and 5.0 return error code 16h on CL=45h,65h if the device
does not support a retry counter
SeeAlso: AX=440Dh,INT 2F/AX=0802h,INT 2F/AX=122Bh,INT 2F/AX=14FFh
SeeAlso: INT 2F/AX=1A01h

(Table 0691)
Values for IOCTL category code:
00h unknown (DOS 3.3+)
01h COMn: (DOS 3.3+)
03h CON (DOS 3.3+)
05h LPTn:
9Eh Media Access Control driver (STARLITE)
00h-7Fh reserved for Microsoft
80h-FFh reserved for OEM/user-defined

(Table 0692)
Values for generic character IOCTL function:
00h MAC driver Bind (STARLITE)
45h set iteration (retry) count
4Ah select code page
4Ch start code-page preparation
4Dh end code-page preparation
5Fh set display information (DOS 4+)
65h get iteration (retry) count
6Ah query selected code page
6Bh query prepare list
7Fh get display information (DOS 4+)
Note: bit assignments for function code:
bit 7: set to ignore if unsupported, clear to return error
bit 6: set if passed to driver, clear if intercepted by DOS
bit 5: set if queries data from device, clear if sends command
bits 4-0: subfunction

Format of parameter block for function 00h:
Offset Size Description (Table 0693)
00h 8 BYTEs ASCIZ signature "STARMAC"
08h WORD version
0Ah WORD flags
bit 0: media requires connect or listen request before use
bit 1: network is a LAN (broadcast/multicast supported)
bit 2: point-to-point network
0Ch WORD handle for use with MAC driver's private interface (filled in
by MAC driver)
0Eh WORD context
10h WORD approximate speed in KB/sec (filled in by MAC driver)
12h WORD approximate cost in cents per hour (filled in by MAC driver)
14h WORD maximum packet size in bytes (filled in by MAC driver)
16h WORD addressing format (filled in by MAC driver)
0000h general addressing
0001h Ethernet addressing
0002h Token Ring addressing
0003h Token Bus addressing
18h DWORD Send entry point (filled in by MAC driver)
1Ch DWORD RegisterEventHandler entry point (filled in by MAC driver)
20h DWORD SetPacketFilter entry point (filled in by MAC driver)
24h DWORD UnBind entry point (filled in by MAC driver)

Format of parameter block for function 45h:
Offset Size Description (Table 0694)
00h WORD number of times output is attempted before driver assumes
device is busy

Format of parameter block for functions 4Ah and 6Ah:
Offset Size Description (Table 0695)
00h WORD length of data
02h WORD code page ID
04h 2N BYTEs DCBS (double byte character set) lead byte range
start/end for each of N ranges (DOS 4.0)
WORD 0000h end of data (DOS 4.0)

Format of parameter block for function 4Ch:
Offset Size Description (Table 0696)
00h WORD flags
DISPLAY.SYS = 0000h
PRINTER.SYS bit 0 clear to prepare downloaded font, set to
prepare cartridge selection
02h WORD length of remainder of parameter block
04h WORD number of code pages following
06h N WORDs code page 1,...,N

Format of parameter block for function 4Dh:
Offset Size Description (Table 0697)
00h WORD length of data
02h WORD code page ID

Format of parameter block for functions 5Fh and 7Fh:
Offset Size Description (Table 0698)
00h BYTE level (0 for DOS 4.x-6.0)
01h BYTE reserved (0)
02h WORD length of following data (14)
04h WORD control flags
bit 0 set for blink, clear for intensity
bits 1-15 reserved
06h BYTE mode type (1=text, 2=graphics)
07h BYTE reserved (0)
08h WORD colors
0000h = monochrome
else N bits per pixel
0Ah WORD pixel columns
0Ch WORD pixel rows
0Eh WORD character columns
10h WORD character rows

Format of parameter block for function 6Bh:
Offset Size Description (Table 0699)
00h WORD length of following data
02h WORD number of hardware code pages
04h N WORDs hardware code pages 1,...,N
WORD number of prepared code pages
N WORDs prepared code pages 1,...,N
--------d-21440C-----------------------------
INT 21 - Greg Shenaut ASPITAPE.SYS - INTERFACE
AX = 440Ch
BX = device handle
CH = category code
07h tape (ASPITAPE.SYS)
CL = function
01h "mtop" - perform tape operation
02h "mtget" - get tape status
03h ignore end-of-tape errors
04h enable end-of-tape errors
DS:DX -> parameter block (see #0700,#0701)
Return: CF set on error
AX = error code (see #0811 at AH=59h)
CF clear if successful
DS:DX -> data block
Notes: This device driver is a simple DOS interface to the Adaptec Advanced
SCSI Programming Interface (ASPI). It provides the following device
names as access to the SCSI tape, 'RMTx' (rewind on close) and
'NRMTx' (NO rewind on close) where x can go from 0 to 3. There may
also be the following names 'MTx' and 'NMTx' which default to 1024
byte blocks. The names may also have a '$' appended to try and make
them unique from file names of 'RMT0' etc.
once opend these devices must be put into RAW mode
SeeAlso: AX=4402h"ASPI"

Format of ASPITAPE.SYS mtop parameter block:
Offset Size Description (Table 0700)
00h WORD operation code
00h "MTWEOF" - write an end-of-file record
01h "MTFSF" - forward space file
02h "MTBSF" - backward space file
03h "MTFSR" - forward space record
04h "MTBSR" - backward space record
05h "MTREW" - rewind
06h "MTOFFL" - rewind and unload
07h "MTNOP" - perform TEST UNIT READY
02h DWORD repetition count

Format of ASPITAPE.SYS mtget parameter block:
Offset Size Description (Table 0701)
00h BYTE ASPI host ID
01h BYTE SCSI target ID
02h BYTE SCSI logical unit number
03h BYTE device parameters
bit 0: drive must use fixed-block read and write
bit 7: drive is an ASPI device
04h BYTE current device state (see #0702)
05h BYTE unit number within driver
06h WORD fixed block blocksize
08h BYTE last SCSI status
09h BYTE last SCSI sense key
0Ah WORD last SCSI opcode (packed) (see #0703)
0Ch WORD residual bytes from SCSI opcode

Bitfields for ASPITAPE.SYS current device state:
Bit(s) Description (Table 0702)
0 device currently opened in buffered mode
1 drive currently opened in nonbuffered mode
2 rewind drive on last close
3 drive has been written on
4 drive has been read from
5 next read will return 0 bytes
6 EOM will resemble EOF
7 drive may be busy rewinding

Bitfields for SCSI opcode:
Bit(s) Description (Table 0703)
0-7 SCSI operation (SCSI packet byte 0)
8-10 SCSI flags (SCSI packet byte 1)
11-12 ASPI "Direction Bits" (ASPI SRB byte 3)
--------D-21440D-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC BLOCK DEVICE REQUEST
AX = 440Dh
BL = drive number (00h=default,01h=A:,etc)
CH = category code (see #0704)
CL = minor code (function) (see #0705)
DS:DX -> (DOS) parameter block (see #0706,#0708,#0709,#0710,#0711)
SI:DI -> (OS/2 comp box) parameter block (see #0712,#0713,#0714,#0715)
Return: CF set on error
AX = error code (01h,02h) (see #0811 at AH=59h)
CF clear if successful
DS:DX -> data block if CL=60h or CL=61h
Notes: DOS 4.01 seems to ignore the high byte of the number of directory
entries in the BPB for diskettes.
functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5+
the DUBLDISK.SYS v2.6 driver only supports minor codes 60h and 67h
DR-DOS 3.41-6.0 only support minor codes 40h-42h and 60h-62h; all
other minor codes return error code 16h
some PCMCIA calls reportedly appear to be dangerous for MS-DOS versions
prior to 5.0
SeeAlso: AX=440Ch,AH=69h,INT 2F/AX=0802h,INT 2F/AX=122Bh

(Table 0704)
Values for block device IOCTL category code:
08h disk drive
00h-7Fh reserved for Microsoft
80h-FFh reserved for OEM/user-defined

(Table 0705)
Values for generic block IOCTL minor code:
00h (OS/2) \ used to lock/unlock a drive
01h (OS/2) /
40h set device parameters
41h write logical device track
42h format and verify logical device track
46h (DOS 4+) set volume serial number (see also AH=69h)
47h (DOS 4+) set access flag
50h (PCMCIA) attribute memory write
51h (PCMCIA) common memory write
52h (PCMCIA) force media change (DOS 5+ ???)
53h (PCMCIA) erase drive
54h (PCMCIA) erase media
56h (PCMCIA) set erase status callback
57h (PCMCIA) append Card Information Structure (CIS) tuple
58h (PCMCIA) erase CIS tuples
60h get device parameters
61h read logical device track
62h verify logical device track
66h (DOS 4+) get volume serial number (see also AH=69h)
67h (DOS 4+) get access flag
68h (DOS 5+) sense media type
70h (PCMCIA) attribute memory read
73h (PCMCIA) get memory media information (DOS 5+ ???)
76h (PCMCIA) get erase status callback
77h (PCMCIA) get first Card Information Structure (CIS) tuple
78h (PCMCIA) get next CIS tuple
7Fh (PCMCIA) get ??? information

Format of parameter block for functions 40h, 60h:
Offset Size Description (Table 0706)
00h BYTE special functions
bit 0 set if function to use current BPB, clear if Device
BIOS Parameter Block field contains new default BPB
bit 1 set if function to use track layout fields only
must be clear if CL=60h
bit 2 set if all sectors in track same size (should be set)
bits 3-7 reserved
01h BYTE device type (see #0707)
02h WORD device attributes
bit 0 set if nonremovable medium
bit 1 set if door lock ("changeline") supported
bits 2-15 reserved
04h WORD number of cylinders
06h BYTE media type
for 1.2M drive
00h 1.2M disk (default)
01h 320K/360K disk
F8h for DUBLDISK.SYS v2.6 expanded drives
always 00h for other drive types
07h 31 BYTEs device BPB (see #0801 at AH=53h), bytes after BPB offset 1Eh
omitted
---function 40h only---
26h WORD number of sectors per track (start of track layout field)
(maximum 63)
28h N word pairs: number,size of each sector in track

(Table 0707)
Values for device type:
00h 320K/360K disk
01h 1.2M disk
02h 720K disk
03h single-density 8-inch disk
04h double-density 8-inch disk
05h fixed disk
06h tape drive
07h (DOS 3.3+) other type of block device, normally 1.44M floppy
08h read/write optical disk
09h (DOS 5+) 2.88M floppy

Format of parameter block for functions 41h, 61h:
Offset Size Description (Table 0708)
00h BYTE special functions (reserved, must be zero)
01h WORD number of disk head
03h WORD number of disk cylinder
05h WORD number of first sector to read/write
07h WORD number of sectors
09h DWORD transfer address

Format of parameter block for function 42h:
Offset Size Description (Table 0709)
00h BYTE reserved, must be zero (DOS <3.2)
bit 0=0: format/verify track
1: format status call (DOS 3.2+), don't actually format
bits 1-7 reserved, must be zero
value on return (DOS 3.3+):
00h specified tracks, sectors/track supported by BIOS
01h function not supported by BIOS
02h specified tracks, sectors/track not allowed for drive
03h no disk in drive
01h WORD number of disk head
03h WORD number of disk cylinder

Format of parameter block for function 62h:
Offset Size Description (Table 0710)
00h BYTE reserved, must be zero (DOS <3.2)
bit 0=0: verify single track
1: verify multiple tracks
bits 1-7 reserved, must be zero
value on return (DOS 3.3+):
00h specified tracks, sectors/track supported by BIOS
01h function not supported by BIOS
02h specified tracks, sectors/track not allowed for drive
03h no disk in drive
01h WORD number of disk head
03h WORD number of disk cylinder
05h WORD number of tracks to verify (equivalent to 255 or fewer sectors)

Format of parameter block for functions 46h, 66h:
Offset Size Description (Table 0711)
00h WORD (call) info level (should be 0000h)
02h DWORD disk serial number (binary)
06h 11 BYTEs volume label or "NO NAME "
11h 8 BYTEs filesystem type "FAT12 " or "FAT16 " (CL=66h only)

Format of parameter block for functions 47h, 67h:
Offset Size Description (Table 0712)
00h BYTE special-function field (must be zero)
01h BYTE disk-access flag, nonzero if access allowed by driver

Format of parameter block for function 52h:
00h BYTE (call) unused??? (Table 0713)
(return) 00h if flash/ATA drive but no card inserted
unchanged otherwise
Notes: the absense of a flash card should be tested by checking the DOS error
code rather than the returned byte
the parameter byte is cleared to 00h erroneously by the Award
PCDISK.EXE v1.02c PCMCIA/ATA driver if no ATA card is inserted
(bug corrected in PCDISK.EXE v1.02h and later)
not supported by the SystemSoft ATADRV.EXE and the Phoenix PCMATA.SYS
PCMCIA/ATA drivers

Format of parameter block for function 68h:
Offset Size Description (Table 0714)
00h BYTE 01h for default media type, 00h for any other media type
(see also INT 13/AH=20h"Compaq")
01h BYTE 02h for 720K, 07h for 1.44M, 09h for 2.88M

Format of parameter block for function 73h:
Offset Size Description (Table 0715)
00h BYTE ???
00h ATA card inserted ???
80h ATA card not inserted ???
01h BYTE length of parameter block ???
apparently always 40h
02h BYTE ???
00h ATA card not inserted ???
0Dh ATA card inserted ???
03h 2 BYTEs ??? (apparently always 00h)
05h BYTE drive number (0=first) ???
06h BYTE total number of drives ???
07h BYTE ???
00h ATA card not inserted ???
01h ATA card inserted ???
08h 17 BYTEs ???
19h BYTE ???
00h ATA card not inserted ???
01h ATA card inserted ???
1Ah BYTE ??? (apparently always 01h)
1Bh BYTE ???
00h ATA card not inserted ???
01h ATA card inserted ???
1Ch 2 BYTEs ??? (apparently always 0015h)
1Eh 2 BYTEs ???
20h 2 BYTEs ??? (apparently always 0110h)
22h 15 BYTEs ???
31h 2 BYTEs ??? (apparently always 7000h)
33h 11 BYTEs driver signature
"AWARD PDISK" for Award PCDISK.EXE PCMCIA/ATA driver
3Eh 2 BYTEs ???
Note: this function is not supported by the SystemSoft ATADRV.EXE and the
Phoenix PCMATA.SYS PCMCIA/ATA drivers

Format of parameter block for function 7Fh for SystemSoft ATADRV.EXE:
Offset Size Description (Table 0716)
00h DWORD -> unknown location within driver
Note: function supported by the SystemSoft ATADRV.EXE PCMCIA/ATA driver
but not by the Award PCDISK.EXE PCMCIA/ATA driver

Format of parameter block for function 7Fh for Phoenix PCMATA.SYS:
Offset Size Description (Table 0717)
00h 8 BYTEs ???
Note: this function supported by the Phoenix PCMATA.SYS PCMCIA/ATA driver
but not by the Award PCDISK.EXE PCMCIA/ATA driver
--------D-21440E-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GET LOGICAL DRIVE MAP
AX = 440Eh
BL = drive number (00h=default,01h=A:,etc)
Return: CF set on error
AX = error code (01h,0Fh) (see #0811 at AH=59h)
CF clear if successful
AL = 00h block device has only one logical drive assigned
1..26 the last letter used to reference the drive (1=A:,etc)
Note: DR-DOS 3.41-5.0 DRIVER.SYS does not support drive mapping and thus
always returns AL=00h
SeeAlso: AX=440Fh,INT 2F/AX=122Bh
--------D-21440F-----------------------------
INT 21 - DOS 3.2+ - IOCTL - SET LOGICAL DRIVE MAP
AX = 440Fh
BL = physical drive number (00h=default,01h=A:,etc))
Return: CF set on error
AX = error code (01h,0Fh) (see #0811 at AH=59h)
CF clear if successful
drive now responds to next logical drive number
Notes: maps logical drives to physical drives, similar to DOS's treatment of
a single physical floppy drive as both A: and B:
DR-DOS 3.41-5.0 DRIVER.SYS does not support drive mapping and thus
always returns an error on this function
SeeAlso: AX=440Eh,INT 2F/AX=122Bh
--------D-214410-----------------------------
INT 21 - DOS 5+ - IOCTL - QUERY GENERIC IOCTL CAPABILITY (HANDLE)
AX = 4410h
BX = handle for device
CH = category code (see #0691)
CL = function code (see #0692)
Return: CF clear if successful
AX = 0000h specified IOCTL function is supported
CF set on error
AL = 01h IOCTL capability not available
Note: a program which wishes to use Generic IOCTL calls beyond those in the
standard DOS 3.2 set may use this call first to see whether a
particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4411h
--------d-214410BXFFFF-----------------------
INT 21 U - NewSpace - ENABLE DRIVER
AX = 4410h
BX = FFFFh
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
Note: compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4411h/BX=FFFFh
--------D-214411-----------------------------
INT 21 - DOS 5+ - IOCTL - QUERY GENERIC IOCTL CAPABILITY (DRIVE)
AX = 4411h
BL = drive number
CH = category code (see #0704)
CL = function code (see #0705)
Return: CF clear if successful
AX = 0000h specified IOCTL function is supported
CF set on error
AL = 01h IOCTL capability not available
Note: a program which wishes to use Generic IOCTL calls beyond those in the
standard DOS 3.2 set may use this call first to see whether a
particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4410h
--------d-214411BXFFFF-----------------------
INT 21 U - NewSpace - DISABLE DRIVER
AX = 4411h
BX = FFFFh
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
Note: compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4410h/BX=FFFFh
--------O-214412-----------------------------
INT 21 O - DR-DOS 5.0-6.0 - DETERMINE DOS TYPE
AX = 4412h
CF set
Return: CF set if not DR-DOS
AX = error code (see #0811 at AH=59h)
CF clear if DR-DOS
DX = AX = version code (see #0719)
Note: this obsolete call, which is no longer supported in Novell DOS 7, is
identical to AX=4452h
SeeAlso: AX=4452h
--------d-214412BXFFFF-----------------------
INT 21 U - NewSpace - INSTALLATION CHECK???
AX = 4412h
BX = FFFFh
Return: AX = PSP segment of NewRes (resident driver for NewSpace)
BX:DX -> ???
CX = ???
SeeAlso: AX=4411h/BX=FFFFh
--------d-214413BXFFFF-----------------------
INT 21 U - NewSpace - GET ???
AX = 4413h
BX = FFFFh
Return: AX = code segment of NewRes (resident driver for NewSpace)
BX = offset of ???
SeeAlso: AX=4412h/BX=FFFFh
--------O-214414-----------------------------
INT 21 OU - DR-DOS 5.0-6.0 - SET GLOBAL PASSWORD
AX = 4414h
DS:DX -> password string (blank-padded to 8 characters)
Desc: Specify the master password for accessing files.
Note: this obsolete call, which is no longer supported in Novell DOS 7, is
identical to AX=4454h
SeeAlso: AX=4454h
--------d-214414BXFFFF-----------------------
INT 21 U - NewSpace - DEBUGGING DUMP
AX = 4414h
BX = FFFFh
Return: debugging dump written to X:\NEWSPACE.SMP
SeeAlso: AX=4413h/BX=FFFFh,AX=44FFh/BX=FFFFh
--------O-2144-------------------------------
INT 21 OU - DR-DOS 5.0-6.0 - HISTORY BUFFER, SHARE, AND HILOAD CONTROL
AH = 44h
AL = 16h to 18h
Note: these obsolete subfunctions (which are no longer supported in Novell
DOS 7) are identical to AX=4456h through 4458h
SeeAlso: AX=4456h,AX=4457h,AX=4458h
--------O-214451-----------------------------
INT 21 - Concurrent DOS v3.2+ - INSTALLATION CHECK
AX = 4451h
Return: CF set if not Concurrent DOS
AX = error code (see #0811 at AH=59h)
CF clear if successful
AH = single-user/multiuser nature
10h single-user
AL = operating system version ID (see #0719)
14h multiuser
AL = operating system version ID (see #0718)
Notes: as of Concurrent DOS/XM 5.0 (possibly earlier), the version is stored
in the environment variable VER
use this function if you are looking for multiuser capabilities,
AX=4452h for single-user
this function should never return the single-user values
SeeAlso: AX=4452h,AX=4459h

(Table 0718)
Values for Digital Research operating system version ID:
32h Concurrent PC DOS 3.2
41h Concurrent DOS 4.1
50h Concurrent DOS/XM 5.0 or Concurrent DOS/386 1.1
60h Concurrent DOS/XM 6.0 or Concurrent DOS/386 2.0
62h Concurrent DOS/XM 6.2 or Concurrent DOS/386 3.0
66h DR Multiuser DOS 5.1
67h Concurrent DOS 5.1
--------O-214452-----------------------------
INT 21 - DR-DOS 3.41+ - DETERMINE DOS TYPE/GET DR-DOS VERSION
AX = 4452h ("DR")
CF set
Return: CF set if not DR-DOS
AX = error code (see #0811 at AH=59h)
CF clear if DR-DOS
AX = version code
AH = single-user/multiuser nature
10h single-user
AL = operating system version ID (see #0719)
14h multiuser
AL = operating system version ID (see #0718)
DX modified (see note)
Notes: the DR-DOS version is stored in the environment variable VER
use this function if looking for single-user capabilities, AX=4451h
if looking for multiuser; this call should never return multiuser
values
in DR-DOS 3.41-6.0, DX=AX on return; for Novell DOS 7, DH=AH but DL=00h
(reportedly, DH=00h when booting NWDOS7 from installation disks)
Novell DOS 7 returns error code 0001h if SETVER 255.x is in effect for
the calling program
SeeAlso: AX=4412h,AX=4451h,AX=4459h

(Table 0719)
Values for Digital Research operating system version ID:
60h DOS Plus
63h DR-DOS 3.41
64h DR-DOS 3.42
65h DR-DOS 5.00
67h DR-DOS 6.00
70h PalmDOS
71h DR-DOS 6.0 March 1993 "business update"
72h Novell DOS 7.0
--------O-214454-----------------------------
INT 21 U - DR-DOS 3.41+ - SET GLOBAL PASSWORD
AX = 4454h
DS:DX -> password string (blank-padded to 8 characters)
Desc: Specify the master password for accessing files.
SeeAlso: AX=4303h,AX=4414h
--------O-214456-----------------------------
INT 21 U - DR-DOS 5.0+ - HISTORY BUFFER CONTROL
AX = 4456h
DL = control flags (see #0720)
Return: AL = previous value of state flags (see #0721)
Note: DR-DOS 6.0 only checks bit 0 and ignores the rest of DL
SeeAlso: #0722

Bitfields for control flags:
Bit(s) Description (Table 0720)
0 whose buffer: 0=application, 1=COMMAND.COM
---Novell DOS 7---
1 toggle HISTORY usage
2 toggle INSERT state
Note: only one bit at a time may be used

Bitfields for state flags:
Bit(s) Description (Table 0721)
0 HISTORY buffer enabled
1 INSERT enabled
2-5 unused
7 whose buffer: 0=application, 1=COMMAND.COM
--------O-214457-----------------------------
INT 21 U - DR-DOS 5.0+ - SHARE/HILOAD CONTROL
AX = 4457h
DH = subfunction
00h enable/disable SHARE
DL = 00h disable
= 01h enable
else Return: AX = ???
01h get HILOAD status
Return: AX = status
0000h off
0001h on
02h set HILOAD status
DL = new state (00h off, 01h on)
Return: AX = ???
other
Return: AX = ???
Note: This was seen called by COMMAND.COM of DR-DOS 6.0; it does not seem
to be supported by Novell DOS 7
SeeAlso: AX=4457h/DX=FFFFh
--------O-214457DXFFFF-----------------------
INT 21 U - DR-DOS 6.0 - GET SHARE STATUS
AX = 4457h
DX = FFFFh
Return: AX = SHARE status
SeeAlso: INT 2F/AX=1000h
--------O-214458-----------------------------
INT 21 U - DR-DOS 5.0+ internal - GET POINTER TO INTERNAL VARIABLE TABLE
AX = 4458h
Return: ES:BX -> internal variable table (see #0722,#0723)
AX = ??? (0B50h for DR-DOS 5.0, 0A56h for DR-DOS 6.0, 0FE4h for
Novell DOS 7)
SeeAlso: AX=4452h

Format of DR-DOS 5.0-6.0 internal variable table:
Offset Size Description (Table 0722)
00h WORD ???
02h WORD segment of ???
04h WORD offset within DOS data segment of history control structure
for COMMAND.COM history buffer (see #0724)
06h WORD offset within DOS data segment of history control structure
for application history buffer (see #0724)
08h BYTE initial history state flags (see #0721)
09h 2 BYTEs ???
0Bh WORD KB of extended memory at startup
0Dh BYTE number of far jump entry points
0Eh WORD segment containing far jumps to DR-DOS entry points (see #0725)
10h WORD (only if kernel loaded in HMA) offset in HMA of first free HMA
memory block (see #0726) or 0000h if none; segment is FFFFh
12h WORD pointer to segment of environment variables set in CONFIG,
or 0000h if already used
---DR-DOS 6.0---
14h WORD (only if kernel loaded in HMA) offset in HMA of first used HMA
memory block (see #0726) or 0000h if none; segment is FFFFh
16h 8 BYTEs ???
1Eh WORD offset in DOS data segment of full COUNTRY.SYS filename
20h 8 BYTEs ???
28h WORD offset in DOS data segment of SHARE hook table
2Ah 2 BYTEs ???
2Ch WORD offset in DOS data segment of far pointer to INT 2F/AX=1000h
handler
Note: the segment used for the DR-DOS 6.0 CONFIG environment variables
(excluding COMSPEC, VER and OS) is only useful for programs/drivers
called from CONFIG.SYS. The word is set to zero later when the area
is copied to the COMMAND.COM environment space. This allows
CONFIG.SYS to pass information to AUTOEXEC.BAT.

Format of Novell DOS 7 internal variable table:
Offset Size Description (Table 0723)
00h ???
1Eh WORD offset of COUNTRY.SYS filename
42h 16 DWORDs pointers to ??? entry points
???

Format of history control structure:
Offset Size Description (Table 0724)
00h WORD segment of buffer
02h WORD size of buffer in bytes
04h WORD ???

Format of kernel entry jump table for DR-DOS 5.0-6.0:
Offset Size Description (Table 0725)
00h 5 BYTEs far jump to kernel entry point for CP/M CALL 5
05h 5 BYTEs far jump to kernel entry point for INT 20
0Ah 5 BYTEs far jump to kernel entry point for INT 21
0Fh 5 BYTEs far jump to kernel entry point for INT 22 (RETF)
14h 5 BYTEs far jump to kernel entry point for INT 23 (RETF)
19h 5 BYTEs far jump to kernel entry point for INT 24
1Eh 5 BYTEs far jump to kernel entry point for INT 25
23h 5 BYTEs far jump to kernel entry point for INT 26
28h 5 BYTEs far jump to kernel entry point for INT 27
2Dh 5 BYTEs far jump to kernel entry point for INT 28
32h 5 BYTEs far jump to kernel entry point for INT 2A (IRET)
37h 5 BYTEs far jump to kernel entry point for INT 2B (IRET)
3Ch 5 BYTEs far jump to kernel entry point for INT 2C (IRET)
41h 5 BYTEs far jump to kernel entry point for INT 2D (IRET)
46h 5 BYTEs far jump to kernel entry point for INT 2E (IRET)
4Bh 5 BYTEs far jump to kernel entry point for INT 2F
Notes: all of these entry points are indirected through this jump table
to allow the kernel to be relocated into high memory while leaving
the actual entry addresses in low memory for maximum compatibility
some of these entry points (22h,23h,24h,2Eh,2Fh) are replaced as soon
as COMMAND.COM is loaded, and return immediately to the caller, some
returning an error code (the original handler for INT 2F returns
AL=03h [fail]).

Format of HMA Memory Block (DR-DOS 6.0 kernel loaded in HMA):
Offset Size Description (Table 0726)
00h WORD offset of next HMA Memory Block (0000h if last block)
02h WORD size of this block in bytes (at least 10h)
04h BYTE type of HMA Memory Block (interpreted by MEM)
00h system
01h KEYB
02h NLSFUNC
03h SHARE
04h TaskMAX
05h COMMAND
05h var TSR (or system) code and data. DR-DOS TSR's, such as KEYB,
hooks interrupts using segment FFFEh instead FFFFh.
--------O-214459-----------------------------
INT 21 - DR MultiUser DOS 5.0 - API
AX = 4459h
CL = function (see INT E0"CP/M")
DS,DX = parameters
Notes: DR-DOS 5.0 and Novell DOS 7 return CF set and AX=0001h
this API is also available on INT E0
SeeAlso: AX=4452h,INT E0"CP/M"
--------N-2144E0-----------------------------
INT 21 U - Sun PC-NFS - API???
AX = 44E0h
DS:DX -> ???
SS:BP -> stack frame (see #0727)
Return: ???
Note: this function is also supported by Beame&Whiteside's BWPCNFS shim; the
description presented here was derived from that shim

Format of PC-NFS stack frame:
Offset Size Description (Table 0727)
00h WORD -> previous stack frame
02h DWORD return address
--------d-2144FFBXFFFF-----------------------
INT 21 U - NewSpace - ???
AX = 44FFh
BX = FFFFh
DX = ???
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
SeeAlso: AX=4414h/BX=FFFFh
--------!---Section--------------------------