An algorithm for an IPO chart

#include<stdio.h>
#include<math.h>

void display_sphere(double radius,double volume) {
  int c;
  puts("       -------");
  puts("    --/       \\--");
  puts("   /             \\");
  puts("  /               \\");
  puts("  |               |");
  puts("  \\               /");
  puts("   \\             /");
  puts("    --\\       /--");
  puts("       -------");
  puts("");
  printf("Volume is %g cubic lengths\n",volume);
  puts("Use the arrow keys or mouse to rotate the sphere about any axis.");
  puts("Press enter to terminate.");
  while ((EOF != (c = getchar())) && ('\n' != c))
    ;
}

#define TAU (2*M_PI)  /* http://www.youtube.com/watch?v=jG7vhMMXagQ */

double compute_sphere_volume(double radius) {
  /* Skip the triple integral and use the formula */
  return (2*TAU/3)*radius*radius*radius;
}

int main() {
  double radius;
  char buffer[30];
  puts("Enter sphere radius:");
  fgets(buffer,26,stdin);
  sscanf(buffer,"%lf ",&radius);
  display_sphere(radius,compute_sphere_volume(radius));
  return 0;
}