Rectangle.c

#include <stdio.h>

int rectangle(double w, double h, double* P, double* S){
   if (w <= 0 || h <= 0){
     return -1;
   }
   *P = 2 * (w + h);
   *S = w * h;
   return 0;
}

int main(){
   double a, b, P, S;
   while (scanf("%lf %lf", &a, &b) != EOF){
       if(!rectangle(a, b, &P, &S)){
        printf("P = %.2lf, S = %.2lf\n", P, S);
       } else {
        fprintf(stderr, "Invalid sizes!\n");
       }
   }
   return 0;
}