Function Prototypes in C

In C programming language, a function prototype is a declaration of a function that tells the compiler about the name of the function, the arguments it takes, and the type of the value it returns (if any). A function prototype is typically placed at the beginning of a program or in a header file to allow the compiler to check the syntax of the function call and avoid errors.

The syntax of a function prototype is as follows:

return_type function_name(argument1_type argument1_name, argument2_type argument2_name, ...);

Here’s an example of how to declare a function prototype in C:

int add(int a, int b);

In this example, we declare a function prototype for a function named “add” that takes two integer arguments “a” and “b” and returns an integer value.

Function prototypes are useful when a function is defined later in the program, or in another source file. By declaring the function prototype, the compiler can check the syntax of the function call and ensure that the function is defined correctly.

Here’s an example of how to use a function prototype in C:

#include 

int add(int a, int b);

int main() {
    int a = 5, b = 10, c;

    c = add(a, b);

    printf("The sum of %d and %d is %d\n", a, b, c);

    return 0;
}

int add(int a, int b) {
    int result = a + b;
    return result;
}

In this example, we declare the function prototype for the “add” function at the beginning of the program. We then call the “add” function in the main function, and define the “add” function later in the program.

Function prototypes are also useful for ensuring that the correct types of arguments are passed to a function. If the function prototype and the function definition do not match in terms of the number or types of arguments, the compiler will generate an error, making it easier to catch and fix errors in the program.