Category : Pascal Source Code
Archive   : INFOS155.ZIP
Filename : PAGE_09.INF

On this page, you will get ALOT of general information about DOS.

DOS version: Your current version. If DR DOS is detected, you also see it's
version.

Infoplus will display the OS/2 version number if you are running
it in a Compatibility box.

Under DOS 5, if you have tried to use the SETVER command to
change the version of DOS that Infoplus normally looks for,
you will be told what it was changed to. (Infoplus knows how
to find the true DOS version, bypassing SETVER.)

OEM serial number: Some versions of DOS support a number.

System date/time: The current date and time as given by DOS. It is shown
in the format of your current country settings.

Command load paragraph: The memory segment where programs are loaded. The
lower this number is, the more memory you have
available.

Ctrl-C check: This is the setting of the BREAK command. When OFF, you can
stop a DOS command when it is print to the screen. When ON,
you can stop it during copies and disk reads.

Disk verify: This is the setting of the VERIFY command. When ON, DOS will
attempt to re-read any data written to disk. It only checks if
it can read it. It does NOT compare what it reads back with
what it wrote.

Switch prefix character: For DOS commands (and some programs) this is the
character you use to let a program know that it is
being given a command (like /H). Many programs are
hard coded to use the '/' character. Many Unix
users prefer using '-'. When the prefix is set to
'-', you can use '/' in paths, instead of '\'.
Starting with DOS 5, this character is set to '/',
and cannot be changed.

\DEV\ prefix: When you access devices such as PRN or LPT1, you can also use
\DEV\PRN. This was probably to make it work similar to Unix.

Reset boot: This is a flag in the BIOS data area that lets the computer
know what to do when you hit CTL-ALT-DEL.

Boot disk: The drive used to boot the computer. This is shown only for DOS
4 or newer.

DOS flags: This is the memory address for special flags that let TSR's and
similar know when it is safe to make a DOS call while another
program is active.

Printer echo: This is toggled by typing Ctl-P, or Ctl-PrtScr. When on, any
text output by DOS will be echoed to the printer.

PrtSc status: This lets you know if Shift-PrtScr is available, and if the
last attempt was successfull.

Memory allocation: When a program is loaded, it can request blocks of
memory from DOS.

There are 3 ways DOS will look for one:

First fit: Start at the bottom of memory, and search
forward until it finds one that is big enough
or larger that what's requested.
Best fit: Search through all available blocks, and find
the one closest to the size requested.
Last fit: Start at the top of memory, and search
backward until it finds one that is big
enough or larger than what's requested.

The default is First fit, and outside of a running
program, any other settings can confuse DOS.

WIth the introduction of DOS 5, there are several
additional ways DOS will look for free memory. The new
ways involve searching the Upper Memory Blocks in
addition to conventional memory.

Buffers: These are the amount of BUFFERS allocated in CONFIG.SYS (or

defaulted to by DOS.)

DOS 4+ also supports up to 8 read-ahead buffers. When a disk is
being read, and the sector being read is immediately after the
one previously read, DOS will read up to 8 sectors immediatlely.
That way, if they are needed, they will come from the read-ahead
buffer, instead of the disk.

DOS 4 also supports placing it's buffers in EMS memory. If so, it
will round the count UP to the next multiple of 30 (30 buffers
fit in each 16K EMS page.) If EMS is being used, INFOPLUS will
tell you which EMS handle is being used. DOS 5 does NOT support
the placing of buffers in EMS memory.

If DOS 5 is loaded high, then the buffers are placed in the HMA.

File handles: Most current programs access files using what's called
'handles'. This is set by the FILES statement in your
CONFIG.SYS. Every program will have 5 of them used. These
are for CON, error device (always the screen,) PRN, AUX
(COM1), and NUL. There is a second 'screen' that gives
detailed information about currently opened files.

File Control Blocks: An older method of access files used special blocks.
These methods were superceeded by handles, although a
few special functions still require using FCBs. The
default by DOS is FCBS=4,0, and typically never needs
changing.

Under DOS 4, FCBs can be dangerous. If a disk drive
partition is larger than 32 Megabytes, some of the
values in the block can 'roll over' at the 32M mark.
This can cause data to write in the wrong place! To
prevent disaster, DOS 4 will attempt to load
SHARE.EXE. SHARE translates FCBs into handles. It also
increases the number of FCBs to 16,8. You can regain
some memory by specifying FCBS=4,1 in your CONFIG.SYS.
This prevents SHARE from increasing the size.

DOS 5 has full support for large disks built-in. DOS 5
does NOT support the second parameter of FCBS= (the
protected FCB parameter.)

Stacks: When an interrupt occurrs, DOS will select a stack that is used to
temporarily store data. This can sometimes cause problems with
programs. There are two values, the number of stacks, and the size.
If no STACKS=x,y is found in CONFIG.SYS, DOS will use 0,0 for a
PC/XT, and 9,128 for all others. You can regain memory by
specifying 0,0. This tells DOS to use the current program stack to
hold data. Some disk caches recommend using STACKS=x,128, where x
is the number of sectors per track of your hard disk.

UMBs: Under DOS 5, Upper Memory Blocks (memory between 640K and 1M) can
be part of the memory allocation chain.

International information: This reports on various settings that programs
can use. This allows programs to display data
in a format that users in many countries are
used to seeing.

The second 'page' of page 9 displays the locations of your file handle
tables. Each table can hold information on several handles. The total
sizes of all tables should add up to the FILES= setting in your CONFIG.SYS.
If you don't specify one, DOS picks a default. Also, under Windows 3 in
enhanced mode, each window can have some private handles of it's own. The
amount is set using the PerVMFILES= entry in SYSTEM.INI, under the [386enh]
section. The default is 10. (If you have FILES=30, you will see 40 files
under Windows.)

Under each table entry is a listing of any open files in that table.
Information is displayed for each one giving which modes it was opened
with, date and time last modified, current size, and owners PSP. You can
use the PSP listing on page 4 to see which program has opened the file.

Most of the time, you will only see 3 files open (CON, AUX, and PRN).
These are the standard DOS devices. You will usually only see other files
if they are being held open by TSR's, or you have shelled out of another
program that didn't close it's files.

Under multitaskers such as Windows or Desqview, you can see most of the
open files. (Under Windows 3 enhanced, each window can have files that are
exclusive to it. You won't see those.) The owner PSP you see may not be
displayed on page 4 if the owner is running in another window.