In standard C programming, is the statement "A function cannot be defined inside another function" true or false with respect to nested function definitions?

Introduction / Context:
Nested functions, where one function is defined inside the body of another, are a feature in some languages. This question asks whether such nested function definitions are allowed in standard C. Understanding what the C standard permits helps you recognize compiler specific extensions versus portable, standard conforming code that will compile across different platforms.

Given Data / Assumptions:

• We are talking specifically about the C programming language as defined by the ISO C standard.

• The statement claims that a function cannot be defined inside another function.

• We treat nonstandard compiler extensions (such as nested functions in some GNU C compilers) as outside the standard.

• The question is effectively a true or false style conceptual check.

Concept / Approach:
In standard C, all function definitions must appear at file scope, not inside other function bodies. You can declare function prototypes inside blocks, but actual function definitions (with a full body) must not be nested. Some compilers offer nested functions as an extension, but such code is not portable and not allowed by the language standard. Therefore, the statement is correct when interpreted in the context of standard C.

Step-by-Step Solution:
Step 1: Recall that in standard C syntax, a function definition has the form return_type name(parameter_list) { /* body */ } and appears at file scope. Step 2: Inside a function body you can write declarations of variables and prototypes, but not another full function definition with its own body. Step 3: The C standard does not define semantics for a function defined inside another, so such constructs are disallowed. Step 4: Certain compilers may accept nested function definitions as nonstandard extensions, but that does not change the definition of standard C. Step 5: Therefore, the statement that a function cannot be defined inside another function is accurate for standard, portable C programs.

Verification / Alternative check:
If you attempt to write code like void outer() { void inner() { /* ... */ } } and compile it with a strictly conforming C compiler that does not enable extensions, you will receive a compilation error. On the other hand, moving inner() outside outer() at file scope makes the code valid. This simple experiment matches the language specification and confirms that nested function definitions are not part of standard C.

Why Other Options Are Wrong:
Option B is wrong because it claims the opposite of what the standard says; C does not "always allow" nested function definitions. Option C is wrong because C itself is not an object oriented language and the restriction on nested function definitions is part of C, not something specific to OO languages. Option D is wrong because no function in C is literally nested inside main; all top level functions, including main, are defined at file scope, and main is just another function from a syntactic viewpoint.

Common Pitfalls:
A common pitfall is using features from a particular compiler (such as nested functions in GNU C) and assuming they are portable C features. Another mistake is confusing nested function definitions with nested calls; functions can certainly call other functions, but that is different from defining one inside the lexical body of another. Always distinguish between declarations (which can appear in blocks) and definitions (which have stricter placement rules in C).

Final Answer:
In standard C, the statement is correct: you cannot define one function inside another function.