CHAPTER 13

770 Chapter 13 Optical Storage
DEVICE=C:\DRIVERS\MYCDROM.SYS /D:mscd001
C:\DRIVERS is the subdirectory that contains the driver MYCDROM.SYS, the driver for your specific
CD-ROM drive.
Note the /D:mscd001 option after the preceding statement. This designation, called the device signature,
identifies this CD-ROM driver as controlling the first (001), and only, CD-ROM drive on the system.
This portion of the device driver statement is for the Microsoft DOS Extensions driver, which
designates CD-ROM drives in this fashion. In fact, you could use any designation here, as long as the
MSCDEX command line uses the same one.
MSCDEX: Adding CDs to DOS/Win3.x
The Microsoft CD Extensions for DOS enable the DOS operating system (and by extension, Windows
3.x) to identify and use data from CD-ROMs attached to the system. The original DOS operating system
had no provisions for this technology, so “hooks” or handling of this unique media are not part
of the basic operating environment. Using these extensions is convenient for all involved, however.
As CD-ROM technology changes, the MSCDEX can be changed, independently of DOS. For example,
most PhotoCD, multiple-session CD-ROM drives require MSCDEX.EXE version 2.21 or higher, which
has been modified from earlier versions to accommodate the newer CD-ROM format.
MSCDEX.EXE should be in your software kit with your drive. If not, you can obtain the latest copy
directly from Microsoft. If you are a registered user of DOS or Windows 3.1, MSCDEX.EXE is free.
Read the licensing agreement that appears on the disc or in your manual concerning the proper
licensing of the MSCDEX files.
Your installation software should add a line similar to the following to your AUTOEXEC.BAT file:
C:\WINDOWS\COMMAND\MSCDEX.EXE /d:mscd001
C:\WINDOWS\COMMAND is the directory in which the MSCDEX.EXE file is located by default with Windows
9x and later; with MS-DOS and Windows 3.1, it could be located in the \DOS directory or in the directory
containing the CD-ROM drivers. The /d:mscd001 portion of the command line supplies the
MSCDEX extension with the device signature defined in the CD-ROM device driver of your
CONFIG.SYS file.
Note
The MSCDEX and CD-ROM device signatures must match. The defaults that most installations provide are used in this
example. As long as the two names are the same, the drivers can find one another.
As long as you have these three drivers—the SCSI adapter driver, the CD-ROM driver, and the DOS
CD extensions—loaded properly in your system, the CD-ROM drive will operate as transparently as
any other drive in your system.
Table 13.30 lists the options you can add to the MSCDEX.EXE command line.
Table 13.30 MSCDEX Command-Line Options
Switch Function
/V Called Verbose; when this option is added to the command line, it displays information
about memory allocation, buffers, drive letter assignments, and device driver names on your
screen at boot time.