How to Detect a DoubleSpace Drive from a Batch File (101884)
The information in this article applies to:
• Microsoft MS-DOS operating system 6.0
• Microsoft MS-DOS operating system 6.2
• Microsoft MS-DOS operating system 6.22
This article was previously published under Q101884
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:
• 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.
• 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
Modification Type: |
Major |
Last Reviewed: |
11/19/1999 |
Keywords: |
KB101884 |
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