Which is a correct function prototype before main for a function that returns int?

• A. void myFunction(int a);
• B. myFunction(int a);
• C. int myFunction(int a);
• D. int myFunction(a);

Answer: (C)

In C, a function prototype before main declares the function’s return type, name, and the types of its parameters so the compiler knows how to call it. For a function that returns an int and takes a single int parameter, the prototype should start with int, then the function name, then a parameter list showing the type int for that parameter, and end with a semicolon. The best form is int myFunction(int a); This clearly communicates that the function returns an int and accepts one int argument.

The other forms don’t fit because they don’t correctly specify the return type or parameter types. One tries to declare a function returning void, which contradicts a function that should return an int. Another omits the return type entirely, which isn’t valid in modern C prototypes. The last one names a parameter but omits its type, which is required in a prototype.