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Question

Hey guys I'm brand new to C++ and I'm having trouble with an equation to change degrees Fahrenheit to degrees Celsius.

// Fahrenheit -> Celcius
if (c==1) {
    cout << "\nPlease give the temperature in degrees Fahrenheit: ";

    cin >> fah;

    cel=(5/9)*(fah-32);

    cout << "\n" << fah << " degrees Fahrenheit corresponds to " << cel << " degrees Celcius.";
}

When I put in a value for fah below 32, my answer in degrees celcius comes back as -0. How can I get a value below 0 for my answer? Btw I used float for all of my variables.

Answer 1

5/9 is integer arithmetic and, therefore, equals 0.

Try (5.0/9) instead to encourage the compiler to use floating point. Alternatively, use (5.f/9) .

Answer 2

The problem is that you're inadvertantly converting to integer - so your fractions will get truncated.

SUGGESTED CHANGE:

if (c==1) {
    cout << "\nPlease give the temperature in degrees Fahrenheit: ";
    cin >> fah;
    cel=(5.0/9.0)*(fah-32.0);
    cout << "\n" << fah << " degrees Fahrenheit corresponds to " << cel << " degrees Celcius.";
}

Answer 3

Try using double instead of int to allow good decimal results not every conversion is one for one

edit: Try changing your 5/9 to a decimal but, copy this code over for referance I set your variable "C" to 1 just so I didnt have to change your original code too much. These arent the most accepted coding practices but its an answer to your question.

// test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <iomanip>

using namespace std;

int main()
{
double c=1;
double fah=0;
double cel=0;

// Fahrenheit -> Celcius
if (c==1) {
cout << "\nPlease give the temperature in degrees Fahrenheit: ";

cin >> fah;

cel=(.5556)*(fah-32);

cout << setprecision(3)<<"\n" << fah << " degrees Fahrenheit corresponds to " << cel << "    degrees Celcius.";
}//endif
system ("pause");
return 0;

}

Answer 4

You could also type-cast (5/9) to a float operation. It can be written as ((float)5/9). That should solve your problem.