Q101884: How to Detect a DoubleSpace Drive from a Batch File
Article: Q101884
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:6.0,6.2,6.22
Operating System(s):
Keyword(s):
Last Modified: 19-NOV-1999
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The information in this article applies to:
- Microsoft MS-DOS operating system versions 6.0, 6.2, 6.22
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This information applies to both Microsoft DoubleSpace and Microsoft
DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands
and filenames.
SUMMARY
=======
MS-DOS batch files cannot distinguish between compressed drives and uncompressed
drives. However, you can use the MS-DOS Debug utility to create a program that
sets an errorlevel depending on whether a drive is compressed with DoubleSpace.
An MS-DOS batch file can then test this errorlevel to determine whether the
drive is a DoubleSpace- compressed drive.
NOTE: Microsoft Product Support Services does not provide support for writing the
Debug script or batch file discussed in this article, or troubleshoot problems
related to compiling, running or using this program or batch file.
MORE INFORMATION
================
This following is an example of how to use the MS-DOS Debug utility to create a
program file called ISDBL.COM. ISDBL.COM determines the following:
- Whether DoubleSpace is loaded in memory
-and-
- Whether a specified drive is a DoubleSpace-compressed drive
ISDBL.COM returns the following errorlevels:
Results Errorlevel
------------------------------------------
DoubleSpace compressed drive 1
DBLSPACE.BIN is not loaded 0
Invalid drive 0
Other errors 0
NOTE: ISDBL.COM tests the current drive if no drive is specified on the command
line.
Creating ISDBL.COM
------------------
ISDBL.COM is created using a Debug script file, which contains all the commands
you would enter from within DEBUG to create ISDBL.COM.
To create ISDBL.COM, follow these steps exactly:
1. Create a text file called C:\ISDBL.SRC using a text editor (such as Windows
Notepad or MS-DOS Editor). This is the Debug script file. C:\ISDBL.SRC should
contain the following lines exactly as they appear.
NOTE: Press the ENTER key at the end of each line below.
A 100
MOV AX,2901
MOV SI,81
MOV DI,012D
INT 21
MOV DL,[012D]
DEC DL
JGE 0119
MOV AH,19
INT 21
MOV DL,AL
MOV AX,4A11
MOV BX,1
INT 2F
MOV AX,4C00
AND BL,80
JZ 012B
INC AL
INT 21
RCX
AE
N ISDBL.COM
W
Q
NOTE: You MUST press the ENTER key twice after the last "INT 21" line and once
after the "Q" at the end of the Debug script.
2. From the MS-DOS command prompt on drive C, enter the following command to
create the ISDBL.COM program:
DEBUG < ISDBL.SRC
Debug reads and follows the instructions in the ISDBL.SRC file. It is
recommended that you do not use this command from within Windows or when
other programs are running. If ISDBL.SRC contains an error, Debug probably is
not told when to quit; therefore, you will have to restart your system. Debug
may even be instructed to cause your system to stop responding (hang). If
this happens, restart your system and examine ISDBL.SRC for accuracy.
If there are no errors in ISDBL.SCR, a few screens of information are
displayed, ending with
<nnnn>:012B INT 21
<nnnn>:012D
-RCX
CX 0000
:AE
-N ISDBL.COM
-W
Writing 000AE bytes
-Q
where <nnnn> is a combination of letters and numbers, the exact
combination of which varies. The remaining information should be exactly as
above if ISDBL.COM was compiled correctly.
Debug places the ISDBL.COM file in the current directory, which in the example
above is C:\. It should be 174 bytes in size.
Using ISDBL.COM
---------------
You can now run the ISDBL.COM program from within a batch file to get information
about a specific drive. Below is an example batch file:
DBLTEST.BAT
-----------
@ECHO OFF
REM This batch file uses ISDB.COM to test a drive to see if it
REM was compressed with DoubleSpace.
REM
REM DBLTEST.BAT assumes that ISDBL.COM in in the current
REM directory or a directory on the MS-DOS Path.
REM
REM The syntax for running this batch file is:
REM DBLTEST <drive>:
REM
REM where <drive>: is the name of the drive to test, for example C:
REM If no drive is specified, the current drive is tested.
REM
ISDBL %1
IF NOT ERRORLEVEL 1 GOTO FAILURE
ECHO The drive %1 is a DoubleSpace compressed drive.
GOTO END
:FAILURE
ECHO The drive %1 is not a DoubleSpace compressed drive.
:END
How ISDBL Works
---------------
In determining whether the drive is compressed, ISDBL assumes that DoubleSpace is
running.
ISDBL checks the specified drive by using Interrupt 2F, function 4A11. This
function is the DSGetDriveMapping application programming interface (API) call
for DoubleSpace. If the drive is compressed, then Bit 7 of BL will be set.
Otherwise, it is zero. This result is simply returned at the end of ISDBL.
REFERENCES
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Additional query words: 6.00 6.20
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Keywords :
Technology : kbMSDOSSearch kbMSDOS622 kbMSDOS620 kbMSDOS600
Version : MS-DOS:6.0,6.2,6.22
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