Handling Input to Avoid Program Crashes

Instead of doing what the original author does (which is read a string and convert it manually into a number) why not use streams properly?

When a program wants a number, read a number and then check the stream state is still good. If it's not you know the user has entered something that's not a number. If the stream's in an error state you can clear the error, bin the rest of the input and ask them to start again...

#include <iostream>
#include <string>

int main()
try
{
    while( std::cin )
    {
        std::cout << "I convert temperatures from centigrade to fahrenheit\n"
                     "Please enter a temperature in centigrade for me"
                     " to convert(CTRL+Z to exit): ";

        double centigrade = 0.0;
        std::cin >> centigrade;
        if( std::cin.good() )
        {
            std::cout << "You entered " << centigrade << "C\n"
                      << "That's equivalent to "
                      << centigrade * 9.0 / 5.0  + 32 << "F" << std::endl;
        }
        else if( !std::cin.eof() )
        {
            std::cout << "You're such a kidder!" << std::endl;
            std::cin.clear();
            std::string junk;
            std::getline( std::cin, junk );
        }
    }
}
catch( std::exception &e )
{
    std::cout << "Something went wrong: " << e.what() << std::endl;
}
catch( ... )
{
    std::cout << "Something went wrong, no idea what!" << std::endl;
}

While it's still possible to stuff up the input to the program you won't get anything that causes it to crash. (Please treat this assertion as a challenge and if you manage it I can improve the code).

Oh, and if you're on Linux/UNIX you want to press CTRL+D to exit the program.

Cheers,

Ash

PS: Edited to add the include directives, the compiler considers it a bit rude to leave them out.

PPS: Edited again so the angle brackets showed up... grrr...