Q62214: Calling API Function to Get All Available Drives
Article: Q62214
Product(s): See article
Version(s): 6.00 6.00b 7.00
Operating System(s): OS/2
Keyword(s): ENDUSER | SR# S900517-71 | mspl13_basic
Last Modified: 7-JUN-1990
Microsoft BASIC Compiler versions 6.00 and 6.00b and Microsoft BASIC
Professional Development System (PDS) version 7.00 protected mode
programs can call the OS/2 API function DosQCurDisk() to get all the
available logical drives. DosQCurDisk() requires the following
parameters:
Parameter Description
--------- -----------
PTR WORD Receives current drive code (1 = A, 2 = B, etc.)
PTR DWORD Receives logical drive bitmap (logical drives A-Z
correspond to bits 0-25; a bit is set if a
logical drive exists)
The first parameter is not important in getting the available drives,
but it is worthy to note that for API functions, a WORD (2 bytes) has
a BASIC type of INTEGER. Likewise, a DWORD (4 bytes) has a BASIC type
of LONG. Since the specification requires pointers to these data
items, the DECLARE statement for DosQCurDisk() uses the SEG keyword for
each of the parameters. This causes 4-byte addresses of the parameters
to be passed instead of 2-byte addresses, which is the default because
BASIC uses the medium-memory model. Also, API functions return an
error code, so for BASIC to retrieve this code, you must declare
DosQCurDisk() as a FUNCTION.
This information applies to Microsoft BASIC Compiler versions 6.00 and
6.00b for MS OS/2 and Microsoft BASIC (PDS) version 7.00 for MS OS/2.
For more information on calling OS/2 API functions from Microsoft
BASIC Compiler versions 6.00 and 6.00b, see Page 21 of the "Microsoft
BASIC Compiler 6.0: User's Guide" included with the product.
For more information on calling OS/2 API functions from Microsoft
BASIC PDS version 7.00, see Page 523 of the "Microsoft BASIC 7.0:
Programmer's Guide" included with the product.
For more information on DosQCurDisk(), see Page 547 of "Advanced OS/2
Programming," by Ray Duncan (Microsoft Press, 1989).
To see a BASIC PDS 7.00 sample program that finds all the available
drives in DOS or OS/2 real mode, query in this Knowledge Base on the
word "chdrive".
The following sample program (LOGICAL.BAS) reports all the available
logical drives.
To compile the program, use the following:
bc logical /lp;
To link the program for BASIC 6.00 and 6.00b, use the following:
link /nop logical,,,doscalls;
To link the program for BASIC 7.00, use the following:
link /nop logical,,,os2;
Code Example
------------
' This declaration was taken from the include file
BSEDOSFL.BI.
DECLARE FUNCTION DosQCurDisk% (SEG CurrentDrive AS INTEGER,_
SEG DriveBitmap AS LONG)
' CurrentDrive% receives the current drive code (A=1, B=2,
' etc.). DriveBitmap& receives a bitmap of each logical
' drive's availability.
ErrorCode% = DosQCurDisk% (CurrentDrive%, DriveBitmap&)
IF ErrorCode% THEN
PRINT "An error occurred, the code is";ErrorCode%
ELSE
PRINT "The following drives are available:";
' Bit% is used to circulate through bits 0-25 (drives A-Z)
' of DriveBitmap&. If (DriveBitmap& AND 2^Bit%) = 2^Bit%,
' then bit Bit% of DriveBitmap& is set and the
' corresponding logical drive is available.
FOR Bit% = 0 to 25
IF (DriveBitmap& AND 2^Bit%) = 2^Bit% THEN
PRINT " ";CHR$(Bit% + 65);
END IF
NEXT Bit%
END IF
END
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