1#include <iostream>
 2using namespace std;
 3
 4float c_to_f(float temperature) { return (temperature * (9.0 / 5.0)) + 32.0; }
 5
 6float f_to_c(float temperature) { return (((temperature - 32.0) * 5.0) / 9.0); }
 7
 8int main(void) {
 9  float temperature;
10  char unit;
11
12  cout << "What is the input temperature? ";
13  cin >> temperature;
14
15  cout << "What are the units of the input temperature (C for Celcius or F for "
16          "Fahrenheit)? ";
17  cin >> unit;
18
19  unit = toupper(unit);
20  switch (unit) {
21  case 'C':
22    cout << "Your input temperature is " << temperature << unit;
23
24    if (temperature < -273) {
25      cout << " which is out of range (less than -273C)." << endl;
26      return 1;
27    }
28
29    cout << " which is " << c_to_f(temperature) << "F" << "." << endl;
30    break;
31
32  case 'F':
33    cout << "Your input temperature is " << temperature << unit;
34
35    if (temperature < -416) {
36      cout << " which is out of range (less than -416F)." << endl;
37      return 2;
38    }
39
40    cout << " which is " << f_to_c(temperature) << "C" << "." << endl;
41    break;
42
43  default:
44    cout << "The units you have specified are not one of C (Celcius) or F "
45            "(Fahrenheit)"
46         << endl;
47    return 3;
48  }
49  return 0;
50}