Code

 Header...
// Demonstrate a simple input check

 int main(){
   ... 

»  double minMass, maxMass;

»  while (1) {
»    printf("Please enter the minimum and maximum mass\n");
»    scanf("%lg %lg", &minMass, &maxMass);

»    if (minMass<=0||maxMass<=0) 
      printf("Sorry, the masses must be greater than zero\n");
    else if (minMass>maxMass) 
      printf("Sorry, the maximum must not be less than the minimum\n");
    else 
      break;
  }
  // NB: the above has some non-obvious limitations
  // which we will address later in the course

»  printf("Mass range is %g to %g\n", minMass, maxMass);
  
}

Data