In this article, you will learn and get code about calculating area and circumference of a circle.
To calculate area or circumference of any circle in C programming, you have to ask from user to enter the radius of circle say r. Using this radius, to find area, use 3.14*r*r. And to find circumference, use 2*3.14*r. Here 3.14 is the value of π (Pi)
List of programs, available here in this article:
As area of any circle can be calculated using the formula πr2. Here r represents radius of circle, and the value of π (Pi) is equal to 3.14. So the formula can be written as 3.14r2 or 3.14*r*r. Let's take a look at the program:
// Calculate area of a Circle in C
// ------codescracker.com-------
#include<stdio.h>
#include<conio.h>
int main()
{
float rad, area;
printf("Enter Radius Value of Circle: ");
scanf("%f", &rad);
area = 3.14*rad*rad;
printf("\nArea = %0.2f", area);
getch();
return 0;
}
This program was written under Code::Blocks IDE. Here is the first snapshot of sample run:
Now supply any number as radius value of circle say 5 and press ENTER key to see the output as shown in the second snapshot of sample run:
The format specifier, %0.2f is used to print the value of area upto only two decimal place.
Let's create another program that does the same job but using function as shown here:
// Calculate area of a Circle using Function in C
// ------codescracker.com-------
#include<stdio.h>
#include<conio.h>
float findArea(float);
int main()
{
float rad, area;
printf("Enter Radius Value of Circle: ");
scanf("%f", &rad);
area = findArea(rad);
printf("\nArea = %0.2f", area);
getch();
return 0;
}
float findArea(float rad)
{
return 3.14*rad*rad;
}
After compiling and executing the above program, you will get the same output as seen from the first program's output. To learn more about function, refer to Function in C tutorial.
As circumference of a circle can be calculated using the formula 2πr. Here the value of π is 3.14, and r represents radius of circle. Therefore, after putting the value of π, the formula becomes 2*3.14*r. Here is the program to find circumference of circle:
// Calculate Circumference of Circle in C
// ------codescracker.com-------
#include<stdio.h>
#include<conio.h>
int main()
{
float r, circumf;
printf("Enter Radius Value of Circle: ");
scanf("%f", &r);
circumf = 2*3.14*r;
printf("\nCircumference = %0.2f", circumf);
getch();
return 0;
}
Here is the sample run of above program:
Now let's create another program that does the same job as of previous program, but this time using function.
// Calculate Circumference of Circle using Function in C
// ------codescracker.com-------
#include<stdio.h>
#include<conio.h>
float findCircumf(float);
int main()
{
float r, circumf;
printf("Enter Radius Value of Circle: ");
scanf("%f", &r);
circumf = findCircumf(r);
printf("\nCircumference = %0.2f", circumf);
getch();
return 0;
}
float findCircumf(float r)
{
return 2*3.14*r;
}
This program produce the same output as seen from previous program's output.