HOWTO: Get and Set Diskette Media ID in VB for MS-DOS

ID: Q115238

The information in this article applies to:

Standard and Professional Editions of Microsoft Visual Basic for MS-DOS, version 1.0

SUMMARY

This article shows by example how to call interrupts to get and set the media ID for a diskette. The example also gets and sets the volume serial number and the volume label.

WARNING: One or more of the following functions are discussed in this article; VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, ObjPtr. These functions are not supported by Microsoft Technical Support. They are not documented in the Visual Basic documentation and are provided in this Knowledge Base article "as is." Microsoft does not guarantee that they will be available in future releases of Visual Basic.

MORE INFORMATION

The following example uses MS-DOS interrupt (&h21), functions )&h440D), and minor code (&h46) to set the volume label and serial number for the specified drive.

This information can be found in any MS-DOS programmer's reference, for versions of MS-DOS beyond 5.0.

Code Example


' Note that you will want to load the VBDOS.QLB file when starting
' VBDOS to get this program to run.

' $INCLUDE: 'vbdos.bi'

TYPE midstruc

   midinfolevel AS INTEGER       ' Information level.
   midserialnum AS LONG          ' Serial number.
   midvollabel AS STRING * 11    ' ASCII volume label.
   MidFileSysType AS STRING * 8  ' File system type.

END TYPE

DIM regs AS regtypex
DIM ms AS midstruc

ms.midserialnum = &amp;HFFFFFFFF    ' Set the new volume serial number.
ms.midvollabel = "SIDEHACKERS"

regs.ax = &amp;H440D
regs.bx = 1                     ' Specifies drive A (2 for B, 3 for C..).
regs.cx = &amp;H846
' Remove the apostrophe from the following line to change it from a comment
' to an executed line if you want to retrieve the current values of the
' volume label and the serial number for the specified drive:
' regs.cx = &amp;H866
regs.ds = VARSEG(ms)
regs.dx = VARPTR(ms)

CALL INTERRUPTX(&amp;H21, regs, regs)

CLS

IF (regs.flags AND 1) THEN       ' Check for error.

   PRINT "problem : "; regs.ax   ' Print error number.

ELSE

   PRINT HEX$(ms.midSerialNum)   ' Print successful return values.
   PRINT ms.midVolLabel
   PRINT ms.midFileSysType

END IF

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