THEORY
The stdio.h denotes the C library that we have connected this program to, which contains the code to execute printf command and display results. The printf keyword is used to display content on the screen. It can be used to display strings, numbers as well as values of variables, etc. The scanf command is used to read user input and is used to accept the value of the circle radius from the user. We also know that area of a circle= pi*radius*radius.
FLOWCHART
Algorithm
Step 1: Start
Step 2: Read radius
Step 3: pi=3.14
Step 4: area=pi*radius*radius
Step 5: Print area
Step 6: Stop
C Source Code
#include<stdio.h>
void main()
{
int a,r,pi=3.14;
printf("\n Enter Radius:");
scanf("%d",&r);
a=pi*r*r; //area of circle=pi*radius*radius
printf("\n The area is %d",a);
}