# C Exercises: Compute the perimeter and area of a circle

## C Basic Declarations and Expressions: Exercise-6 with Solution

Write a C program to compute the perimeter and area of a circle with a given radius.

C programming: Area and circumference of a circle

In geometry, the area enclosed by a circle of radius r is πr2. Here the Greek letter π represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter.

The circumference of a circle is the linear distance around its edge.

**Pictorial Presentation:**

Why is the area of a circle of a circle pi times the square of the radius?

**C Code:**

```
#include <stdio.h>
int main() {
int radius; /* Variable to store the radius of the circle */
float area, perimeter; /* Variables to store the area and perimeter of the circle */
radius = 6; /* Assigning a value to the radius */
/* Calculating the perimeter of the circle */
perimeter = 2 * 3.14 * radius;
printf("Perimeter of the Circle = %f inches\n", perimeter);
/* Calculating the area of the circle */
area = 3.14 * radius * radius;
printf("Area of the Circle = %f square inches\n", area);
return(0);
}
```

**Explanation:**

In the exercise above -

- The program includes the standard input/output library <stdio.h>.
- It declares several variables:
- int radius: Represents the circle radius.
- float area and float perimeter: Will store the calculated area and perimeter of the circle.
- In the "main()" function:
- It assigns the value 6 to the 'radius' variable, representing the circle radius.
- The program then calculates the circle's perimeter and area:
- Perimeter: It uses the formula 2*3.14* radius to calculate the circle perimeter and stores the result in the 'perimeter' variable. Here, 3.14 is an approximation of the mathematical constant π (pi).
- Area: It calculates the area using the formula 3.14*radius*radius (π * r^2) and stores the result in the 'area' variable.
- Finally, the program uses the "printf()" function to display the calculated values:
- It prints the calculated perimeter with a message: "Perimeter of the Circle = [perimeter] inches."
- It prints the calculated area with a message: "Area of the Circle = [area] square inches."
- The program returns 0 to indicate successful execution.

Sample Output:

Perimeter of the Circle = 37.680000 inches Area of the Circle = 113.040001 square inches

**Flowchart:**

**C Programming Code Editor:**

**Previous:** Write a C program to compute the perimeter and area of a rectangle with a height of 7 inches. and width of 5 inches.

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