Function Prototype (declaration)

Every function in C programming should be declared before they are used. This type of declaration are also called function prototype. Function prototype gives compiler information about function name, type of arguments to be passed and return type.

Syntax of Function Prototype:

return_type function_name(type(1) argument(1),….., type(n) argument(n));

Here, in the above example, function prototype is “int add(int a, int b);” which provides following information to the compiler:

1.      Name of the function is “add”

2.      Return type of the function is int.

3.      Two arguments of type int are passed to function.

Function prototype is not needed, if you write function definition above the main function. In this program if the code from line 12 to line 19 is written above main(), there is no need of function prototype.