Contents of the MAPDISK.DOC file
MAPDISK Release 3.00 by M. T. Callahan
Copyright (c) 1987, 1988 -- All rights reserved
Purpose This program maps all allocated, and unallocated, extents
for a disk (either floppy or hard). The resulting report
shows ownership of each extent and its starting and ending
position on the disk. The report is written to a user
MAPDSK3x d:  [/F nnnn] [/L nnnn] [/E nnnn]
where x is D for the DOS version
and O for the OS/2 version
d: is the drive to be mapped; there is no
default for drive
is a file specification for the
output report; default is MAPDSK_d, where
d is the drive being mapped. When specified
this MUST be the second parameter.
/F nnnn used to override the default maximum
for the number of files that may be processed.
Default is 5000.
/E nnnn used to override the default maximum
for the number of disk extents that may be
processed. Default is 8192.
/L nnnn used to override the default maximum
for the number of file/extent connections
that may be processed. Default is 10000.
Although a number of other programs have the capability
of mapping a disk, few, if any, show detail down to the
single cluster level.
This release consists of two (2) programs, and this
documentation file. MAPDSK3D.EXE is intended for use
in the PC-DOS environment, and MAPDSK3O.EXE is intended
for use in the OS/2 (protected mode) environment.
This program is intended to be run on an IBM (or very near
clone) PC. To date it has been tested on the IBM XT, AT,
and PS/2 model 60. It has been tested using both PC-DOS
2.x and 3.x operating systems, and the OS/2 1.0 operating
The DOS version of this program uses INT 25 to do absolute
sector READS. As a result it will not work in the OS/2
compatability box, however, since a protected mode OS/2
version of the program is included, this should not be
Both programs are capable of mapping both floppy disks
and hard disks equally well, however, they are most useful
for mapping hard disks.
At this time, neither program supports single disk partitions
of more than 32 Megs. I will release a version that can
handle DOS 4.0's large disk partitions as soon as possible.
Since these programs obtain all of their disk information
from the boot record, they will not work on versions of DOS
or OS/2 that use non-standard boot records.
45K + D + F + E + L + O
D is Directory buffers
- must be large enough to hold all
directories in longest path
- each 512 directory entries requires
16K of memory
- minimum directory size is one
F is 29K per 1000 files
E is 12K per 1000 extents
L is 10K per 1000 file/extent connections
O the OS/2 version is about 2K larger
and will need additional space for the
API functions used
Disk statistics for files and directories will differ from
those returned by CHKDSK in the following ways:
- MAPDISK does not consider the Volume id to be a
file since it only uses a directory entry and not
- The number of directories reported by MAPDISK will
usually be one more than CHKDSK since MAPDISK
reports the root directory as a directory, CHKDSK
- MAPDISK reports all files (SYSTEM, HIDDEN, etc)
in one category, CHKDSK differentiates between
Hidden and non-Hidden files.
This program is supplied AS IS. The author does not
warranty that the program will work as designed on your
particular system. The author will not be liable for any
damages of any kind sustained though the use of this
program on your system. Your use of this program
constitues acceptance of these terms.
This program is intended for the user's personal use.
You may make copies of the program and documentation
for yourself and others, provided no fee is charged.
An exception is made for PC USER'S GROUPS which may
charge a small amount (not to exceed $6) for handling
Although, the author does allow the user to copy this
program and documentation to pass on to others. It is
hoped, that if the user does find this program usefull,
the user will be willing to send the author $10 for the
program to help will future development of this product.
Comments and suggestions are always welcome.
M. T. Callahan
1565 Holly Ave
Rohnert Park, Ca 94928
1.0 1 Oct 1987 - Internal version - proof of concepts
2.0 20 Dec 1987 - First version released to users
3.0 30 Sep 1988 - Corrected minor bug that caused program to loop
- Recoded a number of alogrithms in effort to
- OS/2 protected mode version added
- Added cmd line switches: /F, /E, /L
- Detects more disk and FAT problems than 2.0