#include <stdio.h>
int main()
{
   int circle_radius;
   float PI_VALUE=3.14, circle_area, circle_circumf;

   //Ask user to enter the radius of circle
   printf("\nEnter radius of circle: ");
   //Storing the user input into variable circle_radius
   scanf("%d",&circle_radius);

   //Calculate and display Area
   circle_area = PI_VALUE * circle_radius * circle_radius;
   printf("\nArea of circle is: %f",circle_area);

   //Caluclate and display Circumference
   circle_circumf = 2 * PI_VALUE * circle_radius;
   printf("\nCircumference of circle is: %f",circle_circumf);

   return(0);
}

Enter radius of circle: 2
Area of circle is: 12.560000
Circumference of circle is: 12.560000

/*##Circumference Of Circle*/
/*##Calculation Programs, Datatype Programs, Basic Programs*/

#include<stdio.h>

float PI = 3.14;

int main(){
   float radius, ci;

   printf("\nEnter the radius of Circle : ");
   scanf("%f", &radius);

   ci = 2 * PI * radius;
   
   printf("\nCircumference of Circle : %f", ci);

   return (0);
}

Enter the radius of Circle : 2

Circumference of Circle : 12.560000

#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();

}

enter value of radius=5
Area  = 78.50
circumference = 31.40