1. Write a program in C to find area of circle using single-line comments.

#include<stdio.h>   // include standared header file
#define PI 3.14    // declare constant to store pi value
int main()
{
float r,Area;    // declaring variables
printf("\n Enter the radius of the circle");
scanf("%f", &r);    // read and stores the radius of circle in r variable
Area=PI*r*r;    //calculate the area of circle with given radius
printf("\n The area of the given circle is= %.2f",Area);
return 0;
}
Output:
Enter the radius of the circle: 5
The area of the circle is=78.539749