defining a function in C

Defining a function in C involves specifying the return type, function name, parameters (if any), and the body of the function. Let’s walk through an example of defining a simple function that calculates the square of a number:

#include <stdio.h>

// Function declaration or prototype

int square(int num);

// Function definition

int square(int num) {

    int result = num * num;

    return result;

}

int main() {

    int number = 5;

    int squaredNumber = square(number); // Calling the square function

    printf(“The square of %d is %d\n”, number, squaredNumber);

    return 0;

}

In this example:

1. Function Declaration:
   • Before the main() function, we declare the square() function using a function prototype. This tells the compiler about the function’s existence, its return type (int), and the type of its parameter (int).
2. Function Definition:
   • The square() function is defined after the main() function. It specifies the return type (int), function name (square), and the parameter (int num) within parentheses.
   • Inside the function body, we calculate the square of the num parameter and assign it to a variable result.
   • Finally, we return the result using the return statement.
3. Function Call:
   • Inside the main() function, we call the square() function with an argument (number), which is passed to the num parameter of the square() function.
   • The result returned by the square() function is stored in the variable squaredNumber.
4. Output:
   • The printf() function is used to print the result, displaying the original number and its square.

Defining functions in C allows for code reuse and modularization. Once defined, functions can be called multiple times from different parts of the program, making the code more organized, readable, and easier to maintain.