Declaring and Defining Functions in C programming

Declaring and Defining Functions in C

In C programming, functions are used to perform specific tasks. Functions need to be declared before they are used, and then defined with their actual implementation. Here’s how you can do it:

Function Declaration (Prototype)

A function declaration, or prototype, tells the compiler about the function's name, return type, and parameters, but does not provide the body of the function.

return_type function_name(parameter_list);

Example:

int add(int a, int b); // Function prototype

This declaration tells the compiler that there is a function named add that takes two int parameters and returns an int.

Function Definition

A function definition provides the actual implementation of the function. It includes the function’s body, where the task is performed.

return_type function_name(parameter_list) {
    // Function body
}

Example:

int add(int a, int b) {
    return a + b; // Function body
}

This definition provides the actual code for the add function, which adds the two integer parameters and returns the result.

Example Program

#include <stdio.h>

// Function prototype (declaration)
int add(int a, int b);

int main() {
    int num1 = 5;
    int num2 = 7;
    int result;

    // Function call
    result = add(num1, num2);

    // Print the result
    printf("The sum of %d and %d is %d\\n", num1, num2, result);

    return 0;
}

// Function definition
int add(int a, int b) {
    return a + b;
}

This program demonstrates how to declare and define a function. It includes a function prototype, a function definition, and a function call from the main function.

Note:
Always declare functions before using them in your code to avoid compilation errors. The function prototype provides the necessary information to the compiler about the function's return type and parameters.