When a PC boots, which command category is resident and loaded into main memory so that it is immediately available without loading external files?

Introduction / Context:
DOS-like systems distinguish between internal (resident) and external (on-disk) commands. Understanding which commands are present in memory immediately after boot clarifies why some commands work even when path/drive access is unavailable, while others require loading executable files from disk first.

Given Data / Assumptions:

• System boots successfully to a command interpreter (for example, COMMAND.COM).
• Internal commands are built into the command interpreter image.
• External commands are separate .COM or .EXE files on storage.

Concept / Approach:
Internal commands (for example, DIR, COPY in some versions, CD, CLS, TYPE, REN) are part of the command interpreter and thus reside in memory immediately after boot. External commands (for example, FORMAT, DISKCOPY, CHKDSK in many versions) are separate files and are loaded on demand. Utilities and applications (for example, a word processor) are not resident by default.

Step-by-Step Solution:

Verification / Alternative check:
Attempting to run an external command after removing or unmounting the system disk will fail, while internal commands still function, confirming residency.

Why Other Options Are Wrong:

• External command instructions: Stored on disk; not loaded until invoked.
• Utility programs: Typically external executables; not resident by default.
• Word processing instructions: Application software; not part of boot-resident set.
• None of the above: Incorrect because internal commands are resident.

Common Pitfalls:
Assuming specific commands are always internal across all DOS versions; the internal/external list can vary, but the residency concept remains the same.

Final Answer:
Internal command instructions