Monday, May 16, 2011

Initializing CD-ROM drive under DOS

Initializing CD-ROM drive under DOS

The CD-ROM drive is a block device that is usually recognized automatically under Windows 95/98. Under DOS, to access the CD-ROM drive you must load a device driver in CONFIG.SYS and issue an initialization command in AUTOEXEC.BAT. This is an important thing to know, because there may be times in your trouble-shooting experience with Windows when the graphic interface won't load. You may be forced to boot your computer to a real-mode DOS prompt, and you may need access to the CD-ROM drive to run system diagnostics or reinstall the Windows operating system.

Under Windows 98, if you use the option to create an emergency startup diskette, the drivers to initialize the CD-ROM are automatically copied to the CONFIG.SYS and AUTOEXEC.BAT on the floppy disk This is not done on the emergency boot disk for Windows 95. For the record, the format for these commands is as follows:

The DOS device driver file for the CD-ROM will generally have a name like TEAC_CD.SYS, ATAPI.SYS, SONY55U.SYS, etc. Under Windows 98, Microsoft provides a generic driver called CDROM.SYS that will work with most major brands.

The DOS initialization file for CD-ROM drives is called MSCDEX.EXE. It will generally be located in the DOS directory on your hard disk. (For Windows 95/98, it's stored in the \WINDOWS\COMMAND subdirectory.

To initialize your CD-ROM drive under DOS, place the following statements in your CONFIG.SYS and AUTOEXEC.BAT


DEVICE=[path]\CDROM.SYS /d:mscd0000


[path]\MSCDEX /d:mscd0000

If you are booting from a floppy drive, or if the files are located in the root directory of drive C, you can omit the path information.

the "/d:mscd0000" part of each statement is an arbitrary but necessary designation that identifies the CD-ROM device to the MSCDEX initialization command.