Loading CD-ROM support in DOS In classic DOS setups, where is the device driver for the CD-ROM (for example, OAKCDROM.SYS) typically loaded so that MSCDEX can attach the drive?

Introduction / Context:
Enabling CD-ROM access in DOS requires a device driver and an extension. The low-level hardware driver is loaded early during boot so that higher-level services can bind to it.

Given Data / Assumptions:

• Hardware driver file such as OAKCDROM.SYS is available.
• MSCDEX.EXE (CD-ROM Extensions) provides drive letter and file system integration.
• We are working with DOS 5/6 or Windows 9x DOS mode.

Concept / Approach:

The device driver must be loaded in CONFIG.SYS using a DEVICE= or DEVICEHIGH= line. Afterward, AUTOEXEC.BAT loads MSCDEX.EXE to assign a drive letter and complete access to ISO 9660 file systems.

Step-by-Step Solution:

Verification / Alternative check:

If the driver is missing from CONFIG.SYS, MSCDEX will report no device driver found, confirming that CONFIG.SYS is the correct location for the driver itself.

Why Other Options Are Wrong:

a: AUTOEXEC.BAT loads MSCDEX.EXE (the extension), not the low-level device driver.

b: Control Panel applies to Windows; pure DOS uses text configuration files.

c: “Into Upper Memory” describes placement, not the file to edit. DEVICEHIGH in CONFIG.SYS achieves this.

e: Not applicable because CONFIG.SYS is correct.

Common Pitfalls:

Mismatching the /D: identifier between OAKCDROM.SYS and MSCDEX; forgetting to load HIMEM/EMM386 to create UMBs for DEVICEHIGH.

Final Answer:

CONFIG.SYS