C/C++ fundamentals: At what stage do we 'mention' (provide) the prototype of a function—defining, declaring, prototyping, or calling?

Introduction / Context:A function prototype communicates a function's name, return type, and parameter types to the compiler before the function is used. This is critical for type checking, overload resolution (C++), and correct code generation. The question asks at which stage we provide that prototype in normal C/C++ development flow.

Given Data / Assumptions:

• A function's signature must be known to the compiler before it is called.
• Prototypes are typically placed in header files that are included where needed.
• We distinguish between declaration (prototype) and definition (body).

Concept / Approach:

• A declaration introduces an identifier and its type; for functions, that is the prototype.
• A definition provides the actual function body.
• Calling is the act of invoking a function; it requires that a declaration is already visible.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• Defining: Includes the body; the prototype exists even without the body.
• Prototyping: Not a standard stage name; the correct term is 'declaring'.
• Calling: Requires that the prototype (declaration) already be known.

Common Pitfalls:

• Confusing the term 'prototype' with the implementation; only the signature is needed to call.
• Omitting prototypes leads to implicit declarations (illegal in modern C) or compiler errors.

Final Answer: