MS-DOS startup troubleshooting During a DOS boot, which single function key allows you to step through CONFIG.SYS and AUTOEXEC.BAT line-by-line with confirmation for each command?

Introduction / Context:
When diagnosing startup issues in classic MS-DOS systems, the ability to execute boot files line-by-line is extremely valuable. DOS provides special function keys at boot to bypass or step through CONFIG.SYS and AUTOEXEC.BAT. Knowing the correct key improves troubleshooting speed and safety.

Given Data / Assumptions:

• The environment is MS-DOS (or DOS mode in Windows 9x).
• CONFIG.SYS and AUTOEXEC.BAT contain device drivers and TSR (terminate-and-stay-resident) utilities.
• We want to confirm or skip each line interactively.

Concept / Approach:

At boot, DOS watches for specific keys. F5 bypasses startup files entirely, while F8 triggers step-by-step confirmation. This lets you execute, skip, or modify behavior interactively to isolate failing lines.

Step-by-Step Solution:

Verification / Alternative check:

Compare F8 with F5 on the same machine: F5 loads DOS without processing the files, whereas F8 prompts before each line. This validates the step-through functionality of F8.

Why Other Options Are Wrong:

a: F1 repeats last command in the DOS command processor, not a boot-time step function.

b: F3 recalls previous command line in the shell; unrelated to boot stepping.

c: F5 bypasses startup files completely; it does not step through them.

e: Not applicable because F8 is correct.

Common Pitfalls:

Pressing the key too late; you must hit F8 when the “Starting MS-DOS…” prompt appears. Also, confusing F5 (bypass) with F8 (step).

Final Answer:

F8