C program to find circumference and area of a circle from given radius

Here is a simple C program to find circumference and area of a circle from given radius –

main(){

       float r, pi = 3.1416, c, area;

       printf("\nEnter value of radius>> ");
       scanf("%f", &r);
       while (r > = 0.0){

              c = 2*pi*r;

              area = pi*r*;

              printf("\nCircumference = %f", c);

              printf("\nArea = %f", area);

              scanf("%f", &r)

       }

}