Arizona State University (ASU) CSE100 Principles of Programming with C++ Midterm 1 Practice Exam

In C++, a prototype serves as a declaration for a function that specifies the function’s name, return type, and parameter types. This declaration allows the compiler to understand the function's interface before the actual implementation is encountered in the code. By having the prototype earlier in the code, the compiler can check for correct usage of the function in the main program or other functions, ensuring that calls to the function conform to the defined signature.

This is crucial for type safety, allowing the program to be structured with clear separations between the function declarations and definitions. It facilitates easier debugging and enhances code readability, particularly in large programs where functions may be defined after their first use.

The other options do not correctly characterize a prototype. Detailed comments (the first option) do not define a function's signature. A defined function (the third option) includes the implementation and isn't simply a prototype. Lastly, a block of code that represents a whole program (the fourth option) would encompass everything from function definitions to statements, rather than just the declaration of a specific function.