# 4 : C Program to Calculate Area and Circumfrence of Circle

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This programs asks user to enter the radius of circle and displays the area and circumfrence of circle on the basis of entered radius.

You need to know the formula for Area and circumfrece of circle (included below)

Variables :

1. radius : (Datatype int) : to represent the radius of circle.

2. PI : (Datatype float) : static variable to represent constant PI value upto 3 decimal places i.e 3.142

3. area : (Datatype float) : to store the result of area of the circle being computed.

4. circumfrence : (Datatype float) : to store the result of circumfrence of circle being computed.

Functions :

printf() : is used to display something on the console/screen. Format specifier %d in printf function is used to display a int variable on screen and %f to display float value. \n is used to add a newline

scanf() : is used to fetch data inputted by the user on the console/screen using keyboard. %d in scanf is indicates that inputted text is of type int and %f for float value.

Formula :

Area of Circle : π x r2

Circumfrence of Circle : 2 x π x r

Program :

``````
/*
* This is a C program to Calculate
* the Area and Circumference of
* Circle
*
*
*
* 4_calculate_area_and_circumfrence_of_circle.c
*
*  Created on: Oct 20, 2014
*      Author: Code2care.org
*/

#include <stdio.h>
//#include <conio.h>

void main() {

int radius;
static float PI = 3.142;
float area;
float circumfrence;

//	clrscr();
printf("Program to calculate Area and Circumference of Circle :  \n\n");

printf("Enter the radius of Circle : ");
scanf("%d", &radius);

area = PI*radius*radius;

circumfrence = 2*PI*radius;

printf("\n\nArea of circle with radius %d = %f  \n\n",radius,area);

printf("Circumference of circle with radius %d = %f  \n\n",radius,circumfrence);

//	getch();

}
```
```

• Output :

Program to calculate Area and Circumference of Circle :

Enter the radius of Circle : 5

Area of circle with radius 5 = 78.550003

Circumference of circle with radius 5 = 31.420000

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