C source code to find the area and circumference of a circle

<source lang="c">

1. include <stdio.h>

int main(void) {

   float radius, area, circum;

   printf("Enter radius: ");
   scanf("%f", &radius);
   area   = radius * radius * 22 / 7; /* πr² */
   circum = 2 * radius * 22 / 7;      /* 2πr */
   printf("Area = %f\nCircumference = %f\n", area, circum);

   /* indicate success */
   return 0;

} </source>