Function prototypes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a function prototype in C?

A function prototype is a declaration of a function that specifies its name, return type, and parameters without the function body. It tells the compiler what to expect when the function is called.

beginner

Why do we use function prototypes in C programs?

Function prototypes help the compiler check that functions are called with the correct number and types of arguments, preventing errors before the program runs.

beginner

How do you write a function prototype for a function named add that takes two integers and returns an integer?

The prototype is: <br>int add(int, int);

intermediate

What happens if you call a function without a prototype in C?

If a function is called without a prototype, the compiler assumes it returns an int and does not check the arguments, which can cause unexpected behavior or errors.

beginner

Where should function prototypes be placed in a C program?

Function prototypes are usually placed at the top of the file or in a header file so that all parts of the program know about the functions before they are used.

What does a function prototype in C specify?

A Function body and variables

B Function name, return type, and parameters

C Only the function name

D Only the return type

A function prototype tells the compiler the function's name, return type, and parameter types without the body.

Where is the best place to put function prototypes in a C program?

A At the top of the file or in a header file

B Inside the main function

C After the function definitions

D Anywhere in the middle of the code

Placing prototypes at the top or in header files ensures the compiler knows about functions before they are used.

What happens if you call a function without a prototype in C?

A Program runs perfectly without warnings

B Compiler throws an error immediately

C Compiler assumes it returns int and no argument checks

D Function is ignored

Without a prototype, the compiler assumes the function returns int and does not check arguments, which can cause bugs.

Which of these is a correct function prototype for a function that returns void and takes no parameters?

A void func(void);

B void func();

C func(void);

D void func[];

The correct prototype for a function with no parameters is void func(void); to explicitly specify no arguments.

Why is it important to match the function prototype with the function definition?

A It is not important

B To make the program run faster

C To reduce the size of the executable

D To avoid compiler errors and ensure correct function calls

Matching prototypes and definitions helps the compiler check calls and prevents errors.

Explain what a function prototype is and why it is useful in C programming.

Think about how the compiler knows what a function looks like before it is used.

Describe where and how you would declare function prototypes in a C program.

Consider program organization and compiler needs.