# Computer Programming/Conditions/C++

## conditions.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.
//
// References:
//     https://www.mathsisfun.com/temperature-conversion.html
//     https://en.wikibooks.org/wiki/C%2B%2B_Programming

#include <iostream>

using namespace std;

void ifElse();
void switchCase();
void toCelsius();
void toFahrenheit();

int main()
{
ifElse();
switchCase();
}

void ifElse()
{
char choice;

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

void switchCase()
{
char choice;

cout << "Enter F to convert to Fahrenheit or C to convert to Celsius:" << endl;
cin >> choice;
switch(choice)
{
case 'C':
case 'c':
toCelsius();
break;
case 'F':
case 'f':
toFahrenheit();
break;
default:
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.