DOS command interpreter — which file executes user commands? Identify the DOS system file that functions as the command interpreter (shell) responsible for executing commands typed at the prompt and running batch files.

Introduction / Context:
Classic DOS relies on a command interpreter to process internal commands and dispatch external programs. Knowing the role of each system file helps in troubleshooting boot problems and customizing startup behavior.

Given Data / Assumptions:

• We are discussing MS-DOS/PC-DOS era systems.
• System files include IO.SYS (or IBMBIO.COM), MSDOS.SYS (or IBMDOS.COM), and COMMAND.COM.
• The question asks specifically for the component that executes commands.

Concept / Approach:

COMMAND.COM is the DOS shell. It implements internal commands (DIR, COPY, DEL, etc.), parses the command line, sets up environment variables, and launches external .COM/.EXE/.BAT files. CONFIG.SYS configures drivers and settings at boot; MSDOS.SYS is part of the DOS kernel; SYSTEM.INI is a Windows 3.x/9x configuration file, not a DOS shell.

Step-by-Step Solution:

Verification / Alternative check:

Typing VER or internal commands without any external programs loaded demonstrates the presence of COMMAND.COM. If missing or corrupted, DOS typically fails to provide a command prompt.

Why Other Options Are Wrong:

• MS-DOS.SYS: part of the DOS kernel, not the interpreter.
• CONFIG.SYS: boot-time configuration file, not an executable shell.
• SYSTEM.INI: Windows configuration file; irrelevant to DOS command execution.
• None of the above: incorrect because COMMAND.COM is correct.

Common Pitfalls:

Confusing CONFIG.SYS device directives with command execution; assuming Windows COMMAND.COM behavior is identical to NT's CMD.EXE.

Final Answer:

COMMAND.COM