History of Microsoft MS-DOS CD-ROM Extensions (MSCDEX) (123408)
The information in this article applies to:
• Microsoft CD-ROM Extensions (MSCDEX) for MS-DOS 2.23
• Microsoft CD-ROM Extensions (MSCDEX) for MS-DOS 2.1
• Microsoft CD-ROM Extensions (MSCDEX) for MS-DOS 2.2
• Microsoft CD-ROM Extensions (MSCDEX) for MS-DOS 2.21
• Microsoft CD-ROM Extensions (MSCDEX) for MS-DOS 2.22
This article was previously published under Q123408
This article documents the changes in the Microsoft MS-DOS
CD-ROM Extensions (MSCDEX) from version 2.1 to version 2.23.
MSCDEX version Microsoft product that MSCDEX ships with
2.21 Windows for Workgroups 3.1
2.22 MS-DOS 6.0
2.23 MS-DOS 6.2, 6.21, 6.22, Windows for Workgroups 3.11
Changes from Version 2.1 to 2.2
• Approximately 12K of conventional memory is freed by moving
the dynamic buffers to EMS (expanded memory specification) memory.
• SETUP.EXE now detects EMS memory and automatically uses the
/E option for installation when EMS memory is available.
• A set "Owner ID" bit in the directory entry is now
• The expanded memory interface now avoids writing extraneous
data into the expanded memory buffers of an application.
• Function request #8, Absolute Disk Read, no longer returns
an error when 0 (zero) sectors are requested.
• The MS-DOS version 4.0 interface now returns the "Access
denied" or "File Not Found" error message, as it should, when appropriate.
• The return value of the READ Device Status command now
indicates whether reading of the R-W subchannels is supported. The
corresponding description for obtaining the audio subchannel information has
been expanded to cover the need for obtaining this information concurrently
with audio data.
Changes from Version 2.2 to 2.21
• Version 2.21 corrects the problem that can occur when you
use the /S switch to share a CD-ROM drive on a network and hang the computer.
• Version 2.21 changes the MS-DOS version check to allow
MS-DOS version 5.0, so a SETVER entry is no longer needed.
Changes from Version 2.21 to 2.22
• MSCDEX now loads into UMA. If there is enough memory
available, MSCDEX version 2.21 and earlier can load into upper memory. MSCDEX
version 2.21 and earlier require the load size of MSCDEX (which varies for
different configurations) plus 48K of memory to load. The extra 48K of memory
is added to ensure there is enough memory to load COMMAND.COM.
MSCDEX version 2.22 checks to see if the driver is being loaded above 640K. If
it is, MSCDEX does not add 48K to the initialization load size because it does
not need to be concerned with the transient portion of COMMAND.COM.
• MSCDEX is no longer version dependent. If you are using
MS-DOS 5.0 or 6.0, earlier version of MSCDEX require that you use SETVER.EXE to
tell MSCDEX the MS-DOS version is 4.0.
• The /V switch now reports accurate memory statistics.
Earlier versions of MSCDEX were not accurate.
Changes from Version 2.22 to 2.23
• MSCDEX version 2.22 erroneously assumes that files in a
directory on a CD-ROM are sorted (collated by ASCII code value). Performing a
file search could result in missed files if the files on the CD-ROM are not
sorted. MSCDEX version 2.23 does not assume that the files are sorted but
instead searches the entire directory and does not return a "File not found"
error message unless the file does not actually exist.
• MSCDEX version 2.23 allows files and directory names to
begin with an exclamation point (!), allowing EISA configuration files to be
shipped on CD-ROMs.
NOTE: MSCDEX.EXE version 2.23 has been made available for
customers. Only the English language version of this file is available.
MSCDEX.EXE version 2.23 is available as a self-extracting file named
The following file is available for download from the Microsoft
additional information about how to download Microsoft Support files, click the
following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most
current virus-detection software that was available on the date that the file
was posted. The file is stored on security-enhanced servers that help to
prevent any unauthorized changes to the file.
| Modification Type:
|| Last Reviewed:
||kbgraphxlinkcritical KB123408 kbAudDeveloper|