In classic MS-DOS troubleshooting, which built-in diagnostic utility would you run to view detected serial (COM) ports and other system details?

Introduction / Context:
When diagnosing legacy PCs running MS-DOS, technicians often need to verify which serial (COM) ports the system hardware and BIOS report. MS-DOS provided a small diagnostic program that enumerates hardware, memory, IRQs, and ports, which is especially useful before installing serial-dependent devices like modems or mice.

Given Data / Assumptions:

• Environment: MS-DOS (for example, MS-DOS 5.x or 6.x).
• Goal: Identify detected serial ports (COM1, COM2, etc.).
• Preference: A native DOS utility requiring no third-party tools.

Concept / Approach:
The Microsoft Diagnostics utility, invoked as MSD, displays a menu-driven report including CPU details, memory map, video, IRQ/DMA assignments, and I/O ports. Under the I/O or System Information sections, it lists COM and LPT ports detected via BIOS data structures and direct probing, making it the correct built-in choice for serial port discovery.

Step-by-Step Solution:

Verification / Alternative check:
Cross-check MSD’s report with CONFIG.SYS, AUTOEXEC.BAT, or device manager utilities to confirm consistency. Testing a serial mouse or modem on the listed port further verifies functionality.

Why Other Options Are Wrong:

• command.com: The command interpreter, not a diagnostic tool.
• SDET / serial.chk / comdiag: Not standard MS-DOS utilities for port enumeration.

Common Pitfalls:
Assuming the presence of a COM port guarantees a working device; cabling, IRQ conflicts, or disabled BIOS ports can still block operation.

Final Answer:
MSD