C Program to Calculate the Area and Circumference of a Circle

These are the different ways to calculate the area and circumference of the circle in C programming.
#include<stdio.h>
#include<conio.h>
#define pi 3.14
void main()
{
int r;
float a, c;
printf("ntenter value of radius=");
scanf("%d",&r);
a= pi*r*r;
c=2*pi*r;
printf("tArea = %.2fn",a);
printf("tCircumference = %.2fn",c);
getch();
}
Output

You can also perform this calculate by defining pi as float value.
C Code
#include<stdio.h>
#include<conio.h>
void main()
{
int r;
float a, c;
float pi=3.14;
printf("ntenter value of radius=");
scanf("%d",&r);
a= pi*r*r;
c=2*pi*r;
printf("tArea = %.2fn",a);
printf("tCircumference = %.2fn",c);
getch();
}
Output

You can also perform this calculation by putting value
C Code
#include<stdio.h>
#include<conio.h>
void main()
{
int r;
float a, c;
printf("ntenter value of radius=");
scanf("%d",&r);
a= 3.14*r*r;
c=2*3.14*r;
printf("tArea = %.2fn",a);
printf("tCircumference = %.2fn",c);
getch();
}