C program to find the area of a circle; Through this tutorial, we will learn how to find or calculate the area of a circle using formula, function, and poiter in c programs.

## Programs and Algorithm to Find the Area of a Circle

- Algorithm To Find Area Of a Circle
- C Programs to Find the Area of a Circle using Formula
- C Programs to Find the Area of a Circle using Function
- C Programs to Find the Area of a Circle using Pointer

### Algorithm To Find Area Of a Circle

Use the following algorithm to write a program to find area of a circle; as follows:

- START PROGRAM.
- TAKE RADIUS AS INPUT FROM USER.
- FIND AREA OF A CIRLCE USING THIS FORMULA AREA=3.14*RADIUS*RADIUS.
- PRINT “AREA OF CIRCLE = “
- END PROGRAM.

### C Programs to Find the Area of a Circle using Formula

```
#include<stdio.h>
int main()
{
int r;
float area;
printf("Please enter radius of the circle: ");
scanf("%d",&r);
area=(22*r*r)/7;
printf("The area of circle is: %f\n",area);
return 0;
}
```

The output of the above c program; as follows:

Please enter radius of the circle: 15 The area of circle is: 707.000000

### C Programs to Find the Area of a Circle using Function

```
#include<stdio.h>
float area(int r)
{
return (22*r*r)/7;
}
int main()
{
int r;
float a;
printf("Please enter radius of the circle: ");
scanf("%d",&r);
a=area(r);
printf("area of the circle: %f\n",a);
return 0;
}
```

The output of the above c program; as follows:

Please enter radius of the circle: 5 area of the circle: 78.000000

### C Programs to Find the Area of a Circle using Pointer

```
#include<stdio.h>
void area(int *r,float *a)
{
*a=(22*(*r)*(*r))/7;
}
int main()
{
int r;
float a=1;
printf("Please enter radius of the circle: ");
scanf("%d",&r);
area(&r,&a);
printf("The area of circle is: %f\n",a);
return 0;
}
```

The output of the above c program; as follows:

Please enter radius of the circle: 7 The area of circle is: 154.000000