Programming Fundamentals/Conditions/C++

subroutines.cpp

// This program asks the user to select Fahrenheit or Celsius conversion
// and input a given temperature. Then the program converts the given 
// temperature and displays the result.

#include <iostream>

using namespace std;

void toCelsius();
void toFahrenheit();

int main()
{
    string choice;
    
    cout << "Enter F to convert to Fahrenheit or C to convert to Celsius:" << endl;
    cin >> choice;
    if (choice == string("C") || choice == string("c"))
    {
        toCelsius();
    }
    else if (choice == string("F") || choice == string("f"))
    {
        toFahrenheit();
    }
    else
    {
        cout << "You must enter C to convert to Celsius or F to convert to Fahrenheit!" << endl;
    }
}

void toCelsius()
{
    double f;
    double c;
    
    cout << "Enter Fahrenheit temperature:" << endl;
    cin >> f;
    c = (f - 32) * 5 / 9;
    cout << f << "° Fahrenheit is " << c << "° Celsius" << endl;
}

void toFahrenheit()
{
    double c;
    double f;
    
    cout << "Enter Celsius temperature:" << endl;
    cin >> c;
    f = c * 9 / 5 + 32;
    cout << c << "° Celsius is " << f << "° Fahrenheit" << endl;
}

Try It

Copy and paste the code above into one of the following free online development environments or use your own C++ compiler / interpreter / IDE.

• CodeChef
• GDB Online
• Ideone
• paiza.IO
• PythonTutor
• repl.it
• TutorialsPoint

See Also

• Wikibooks: C++ Programming