Q253678: HOWTO: Detect 16-Bit CD-ROM Drives in Windows 95 and Windows 98

Article: Q253678
Product(s): Microsoft Windows 95.x Retail Product
Version(s): WINDOWS:95,98,98 Second Edition
Operating System(s): 
Keyword(s): kbFileIO kbKernBase kbOSWin95 kbOSWin98 kbDSupport kbGrpDSKernBase
Last Modified: 13-MAY-2002

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The information in this article applies to:

- Microsoft Windows 95 
- Microsoft Windows 98 
- Microsoft Windows 98 Second Edition 
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SUMMARY
=======

An application may need to detect whether the CD-ROM driver employs a 16-bit or
32-bit driver. Because 16-bit CD-ROM drivers do not multitask well, a multimedia
application may choose not to stream information directly from the CD-ROM if a
16-bit driver is being used. This article explains how to detect this system
configuration.

MORE INFORMATION
================

An application can detect whether MSCDEX (the 16-bit driver) or CDFS (the 32-bit
driver) is being used to access the CD-ROM drive by inspecting the number of
sectors per cluster. MSCDEX reports one sector per cluster, whereas CDFS reports
sixteen sectors per cluster. Microsoft Windows NT always uses a 32-bit driver.

The following sample code demonstrates how to use the GetVersion and
GetDiskFreeSpace functions to detect whether the CD-ROM driver is 16-bit or
32-bit:

  #include <windows.h>
  #include <stdio.h>

  /*
   * pszDriveRoot is a string value such as "D:\".
   * It is assumed that the caller has
   * already verified that it refers to a CD-ROM drive.
   */ 
  BOOL IsCDROM16Bit(char *pszDriveRoot)
  {
      DWORD dwSectorsPerCluster, dwDummy;

      /* If Windows NT, then driver is always 32-bit. */ 
      if (!(GetVersion() & 0x80000000))
      {
          return FALSE;
      }

      /* Get the sectors per cluster. */ 
      if (!GetDiskFreeSpace(pszDriveRoot, 
              &dwSectorsPerCluster,
              &dwDummy, 
              &dwDummy,
              &dwDummy))
      {
          return FALSE;
      }

      /* If sectors per cluster is 1, then we are using MSCDEX. */ 
      return dwSectorsPerCluster == 1;
  }

  int main(int argc, char *argv[])
  {
      LPSTR lpstrCDROMDrive = "D:\\";

      if(argc > 1)
          lpstrCDROMDrive = argv[1];

      if (GetDriveType(lpstrCDROMDrive) == DRIVE_CDROM)
      {
          printf("Drive %s is using %d-bit CDROM drivers", lpstrCDROMDrive, IsCDROM16Bit(lpstrCDROMDrive) ? 16 : 32);
      }
      else 
      {
          printf("Drive %s is not a CDROM", lpstrCDROMDrive);
      }
      return 0;
  }

Microsoft provides programming examples for illustration only, without warranty
either expressed or implied, including, but not limited to, the implied
warranties of merchantability and/or fitness for a particular purpose. This
article assumes that you are familiar with the programming language being
demonstrated and the tools used to create and debug procedures. Microsoft
support professionals can help explain the functionality of a particular
procedure, but they will not modify these examples to provide added
functionality or construct procedures to meet your specific needs. If you have
limited programming experience, you may want to contact a Microsoft Certified
Partner or the Microsoft fee-based consulting line at (800) 936-5200. For more
information about Microsoft Certified Partners, please visit the following
Microsoft Web site:

  http://www.microsoft.com/partner/referral/

For more information about the support options that are available and about how
to contact Microsoft, visit the following Microsoft Web site:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

Additional query words:

======================================================================
Keywords          : kbFileIO kbKernBase kbOSWin95 kbOSWin98 kbDSupport kbGrpDSKernBase 
Technology        : kbWin95search kbWin98search kbWin98SEsearch kbZNotKeyword3 kbWin98 kbWin98SE
Version           : WINDOWS:95,98,98 Second Edition
Issue type        : kbhowto

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