Operating systems — command interpreters: What is the primary advantage when a command processor executes only built-in (internal) commands, instead of launching external user-defined commands?

Introduction / Context:
Many operating systems include a command processor (also called a shell) that accepts user commands. Some commands are implemented internally (built-ins) while others are external programs. This question focuses on the performance implications of using only built-in commands versus invoking external executables.

Given Data / Assumptions:

• The command processor can execute built-in commands directly without loading a separate process.
• External commands require locating a program file, loading it from storage, and creating a new process context.
• We are comparing overall execution speed and overhead.

Concept / Approach:

Built-in commands run within the shell process itself. This avoids disk I/O, executable image loading, dynamic linking, and process creation. Eliminating these steps reduces latency for short utility operations such as directory navigation, variable manipulation, or quick configuration changes.

Step-by-Step Solution:

Verification / Alternative check:

Empirical shell timing (for example, time of a built-in echo or cd) is consistently faster than launching an external program of similar function because of the avoided process creation and I/O.

Why Other Options Are Wrong:

• Flexibility via batch files: Batch scripts work with both built-ins and externals; not unique to built-ins.
• Common command set across hardware: Standardization depends on the OS distribution, not on being built-in.
• Users can create system programs: That relates to external commands, not built-ins only.
• None of the above: Incorrect because the speed benefit is real and primary.

Common Pitfalls:

Assuming built-ins are always preferable; sometimes external tools are richer in features. Also, security policies and maintainability may favor external tools despite overhead.

Final Answer:

the processing is much faster than would otherwise be the case when user-defined commands are used