Microsoft KB Archive/58252

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INT 2FH Service 15 MSCDEX and GRAPHICS.COM Conflict PSS ID Number: Q58252 Article last modified on 07-14-1993 PSS database name: O_MSDOS

4.00 4.01


The information in this article applies to:
- Microsoft MS-DOS operating system versions 4.0 and 4.01


The Microsoft CD-ROM Extensions (MSCDEX) version 2.1 and the GRAPHICS.COM utility that is included with MS-DOS versions 4.0 and 4.01 conflict in their usage of INT 2FH, service 15.

GRAPHICS.COM uses this interrupt to check to see if it has been loaded. MSCDEX uses this same interrupt as part of its API to inform an application how many CD-ROM drives are connected (in BX) and which drive letter is being used for the first CD-ROM (in CX).

More Information:

If GRAPHICS.COM is executed before the MSCDEX extensions in the AUTOEXEC.BAT file, MSCDEX hooks in and replaces the GRAPHICS hook. If you press SHIFT+PRINT SCREEN, graphics are printed in landscape mode as they should be.

If you run GRAPHICS.COM again, it checks to see if it is already loaded (via INT 2FH, service 15). GRAPHICS.COM does not understand the information returned by MSCDEX and consequently reloads itself into memory, causing it to hook over MSCDEX. When you run programs that check to see if the MSCDEX extensions have been loaded, they do not get the correct information from INT 2FH, and usually generate an error message.

For example, if you compile and run the *.JRNL files that come with the Programmer’s Library version 1.0, the Programmer’s Library checks for the MSCDEX extensions and terminates with an error message if it does not find the extensions.

Microsoft has confirmed this to be a problem in MS-DOS versions 4.0 and 4.01. This problem does not occur in later versions of MS-DOS.

GRAPHICS.COM is available as an application note titled “MS-DOS 4.0x Patch Disk” (PD0255). Application notes can be obtained by calling Microsoft Product Support Services at (206) 454-2030. This application note is also available from Microsoft OnLine, CompuServe, and GEnie. PD0255 can be found in the Software/Data Library by searching on the keyword PD0255 or S12494. PD0255 was archived using the PKware file-compression utility.

Additional reference words: 4.01 CDROM WINMM appnote pd0255 noupd

Copyright Microsoft Corporation 1993.