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- C program to swap two numbers
- C program to find LCM of two numbers
- C program to find GCD of two numbers
- C program to find LCM and GCD using recursion
- C program to display prime numbers between two numbers using function and without using function
- C program to check whether a string is palindrome or not
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- C program to check whether a number is prime or not
- C program to check whether a number is positive, negative or zero
- C program to check whether a number is palindrome or not
- C program to check leap year
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- C program to calculate the area of square with and without using function
- C program to calculate mean using arrays
- C program to calculate area of circle

In this article, we will illustrate **c program to calculate area of circle**. The formula for the area of the circle is :

Area_circle = Π * r * r

**where,**

mathematical value of Π is 3.14159.

Please go through following articles of c programming, if you do not already know about these topics :

```
#include <stdio.h>
int main() {
float radius, area_circle;
// take radius as input
printf("Enter the radius of circle : ");
scanf("%f", &radius);
area_circle = 3.14 * radius * radius;
printf("Area of circle : %f", area_circle);
return 0;
}
```

**Output**

```
Enter the radius of circle : 10.0
Area of circle : 314
```

In this program first, a user is asked to enter the value of the radius of the circle. After that area is calculated and then displayed.

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```
#include <stdio.h>
//Function declaration
float areaOfcircle(float radius_circle);
int main() {
float radius;
// take radius as input
printf("Enter the radius of circle : ");
scanf("%f", &radius);
printf("Area of circle : %.2f", areaOfcircle(radius));
printf("\n");
return 0;
}
// function definition to calculate area of circle
float areaOfcircle(float radius_circle){
float area_circle;
area_circle = 3.14 * radius_circle * radius_circle;
return area_circle;
}
```

**Output**

```
Enter the radius of circle : 10.0
Area of circle : 314.00
```

This program also calculates and display the area of the circle but only difference is a function name `areaOfcirlce()`

is used to calculate area of circle and return it.