Question

Exercise 5.4

The following program is supposed to convert a temperature in degree Fahrenheit to degree Celsius, but it will not produce the correct result. Use type casting to fix the problem and run the program for the test values. Call your new program ex54.cpp.

Test cases:

32 F is 0 C
212 F is 100 C

PROGRAM:

#include
using namespace std;
int main( )
{
      int t_in_fah, t_in_cel;  //Notice that we declared these two as integers, not the best choice
      cout << "Enter a temperature in Fahrenheit \n";
      cin >> t_in_fah;

      t_in_cel = 5/9*(t_in_fah - 32);
      cout << "The temperature in Celsius is: " << t_in_cel << endl;

     return 0;
}

Answer 1

ERROR: In cpp, *,/ have equal precedence and have left to right associativity so in given expression 5/9*(t_in_fah - 32). 5/9 is calculated to 0 first and everything multiplies by 0 results to 0. To avoid this first do multiplication and then division.

//CODE

#include<iostream>
using namespace std;
int main( )
{
int t_in_fah, t_in_cel; //Notice that we declared these two as integers, not the best choice
cout << "Enter a temperature in Fahrenheit \n";
cin >> t_in_fah;

t_in_cel = 5*(t_in_fah - 32)/9;
cout << "The temperature in Celsius is: " << t_in_cel << endl;

return 0;
}

//OUTPUT