Before going to the program first let us see how to calculate Area and Circumference of a Circle?

To calculate Area and Circumference of a Circle we should know the formulas for Area of a Circle and Circumference of a Circle.

**So the formulas are:**

**Area of a Circle = π × Radius × Radius **

**Circumference of a Circle = 2 × π × Radius**

**Note: The value of π(pi) is 3.14.**

**Example: **Let the value of **radius **be** 5**, then

*Area of a Circle = 3.14 × 5 × 5 = 78.5*

*Circumference of a Circle = 2 × 3.14 × 5 = 31.4*

## Program code to calculate Area and Circumference of a Circle in C:

#include<stdio.h> #include<conio.h> void main() { int r; float area, cir; clrscr(); printf("Enter radius of circle: "); scanf("%d", &r); area = 3.14 * r * r; cir = 2 * 3.14 * r; printf("n Area of a Circle : %.2f ", area); printf("n Circumference of a Circle: %.2f ", cir); getch(); }

## Explanation:

- First the computer reads the value of radius from the user and stores it in the “r” variable using the following lines:

printf("Enter radius of circle: "); scanf("%d", &r);

**Note:** **%d** is used to read the **Integer value.**

- Then using the formulas the Area and Circumference of a Circle is calculated and stored in the “area” and “cir” variables respectively using the following lines:

area = 3.14 * r * r; cir = 2 * 3.14 * r;

- Finally the Area and Circumference of a Circle is printed on the screen using the following lines:

printf("n Area of a Circle : %.2f ", area); printf("n Circumference of a Circle: %.2f ", cir);

**Note:** **%.2f** is used to print the floating-point value with only **2 decimal places.**