C Program to Find Circumference of Circle

In this post, we will learn how to find the circumference of a circle using C Programming language.

The circumference of a circle is its boundary or the length of the complete arc of the circle.

The circumference of the circle can be calculated using the formula 2Ï€r, where ‘r‘ is the radius of the circle and Ï€ = 3.14.

We will be finding the circumference of the circle by using the following methods:

  1. Using Standard Method
  2. Using User-defined Function

So, without further ado, let’s begin this tutorial.

C Program to Find Circumference of Circle

// C Program to Find Circumference of Circle
#include <stdio.h>
int main(){
    float radius, PI = 3.14, cf;
    
    // Asking for input
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);
    
    // Circumference
    cf = 2 * PI * radius;
    
    // Display output
    printf("Circumference of Circle: %.2f", cf);
    return 0;
}

Output

Enter the radius of the circle: 21
Circumference of Circle: 131.88

How Does This Program Work ?

    float radius, PI = 3.14, cf;

In this program, we have declared three float data type variables named radius, Pi and cf.

    // Asking for input
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);

Then, the user is asked to enter the radius of the circle.

    // Circumference
    cf = 2 * PI * radius;

We calculate the circumference of the circle using the formula 2Ï€r. The value of circumference gets stored in the cf named variable.

    // Display output
    printf("Circumference of Circle: %.2f", cf);

Finally, the result is displayed on the screen using printf() function. Here, we have used %.2f format specifier because we want to display the result only till 2 decimal places.

C Program to Find Circumference of Circle Using Function

// C Program to Find Circumference of Circle Using Function
#include <stdio.h>
float circumference(int radius){
    return 2 * 3.14 * radius;
}

int main(){
    float radius, cf;
    
    // Asking for input
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);
    
    // Finding circumference
    cf = circumference(radius);
    
    // Displaying output
    printf("Circumference of the Circle: %.2f", cf);
    return 0;
}

Output

Enter the radius of the circle: 7
Circumference of the Circle: 43.96
float circumference(int radius){
    return 2 * 3.14 * radius;
}

In this program, we have defined a custom function named circumference which returns the circumference of the circle.

    // Finding circumference
    cf = circumference(radius);

Then, we call our custom function in the main function to display the circumference of the circle.

Conclusion

I hope after going through this post, you understand how to find the circumference of a circle using C Programming language.

If you have any doubt regarding the program, feel free to contact us in the comment section. We will be delighted to solve your query.

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