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, letâ€™s begin this tutorial.

Contents

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;

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

// 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: ");
```

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>
return 2 * 3.14 * radius;
}

int main(){

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

// Finding circumference

// 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