# C Program to Find Circle's Area and Circumference

This tutorial will provide the source code of C Program to find the area and circumference of a circle provided we know the diameter or radius of a circle. If we are given Diameter of a circle, then we need to divide it by 2 so that we get the value of radius of circle as most of the calculations we do require radius.

The Formula for calculation of Area of Circle is :

Area of Circle = PI * R * R

While Formula for calculation of Circumference of Circle is :

Circumference of Circle = 2 * PI * R

We have already defined Pi as Floating type variable whose value is fixed as 3.14 for the calculation purposes.

## C Program Source Code to Find Area and Circumference of a Circle

#include<stdio.h> int main() { int radius; float PI=3.14,area,cirf; printf("nEnter the radius of circle: "); scanf("%d",&radius); area = PI * radius * radius; printf("nArea of circle : %f ",area); cirf = 2 * PI * radius; printf("nCircumference : %f ",cirf); return(0); }

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## Output of Program :

Enter radius of a circle : 1 Area of circle : 3.14 Circumference : 6.28

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## What will be the area of circle of radius = 5.5 ?

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