In C programming, functions are self-contained blocks of code that perform a specific task or operation. They allow you to break down a program into smaller, modular pieces, making the code more organized, reusable, and easier to understand.

There is no OOP in C hence there is very basic use of functions in C

 

 

Here is a code to find area of a circle using functions

 

#include <stdio.h>

float calculateArea(float radius)

{

    const float PI = 3.14159;    //decraring a constant

    return PI * radius * radius;

}

 

int main()

{

    float radius;

    printf("Enter the radius of the circle: ");

    scanf("%f", &radius);

 

    // Calculate the area by calling the function

    float area = calculateArea(radius);

 

    // Print the area

    printf("The area of the circle with radius %f is: %f\n", radius, area);

 

}


Output:

Enter the radius of the circle: 5

The area of the circle with radius 5.000000 is: 78.539749

 

In the above code a function with arguments and with a return value is used.

The concept of call by value is used where the value of the actual parameter is copied into the formal parameter and any change made in the formal parameter will not be reflected in the actual parameters.



Recursive Functions:

  

A function that calls itself is a recursive function.

 

Here is a program that finds the factorial of a number using a recursive function

 

#include <stdio.h>

 

int factorial(int n)

{

    if(n==0)

        return 1;

    else

        return n * factorial(n - 1);

}

 

int main()

{

    int num;

    printf("Enter a positive integer: ");

    scanf("%d", &num);

    int fact = factorial(num);

    printf("Factorial of %d = %d\n", num, fact);

}


Output:

Enter a positive integer: 5

Factorial of 5 = 120