Question

What happens if I compare two characters in this way:

if ('a' == 'b')
    doSomething();

I’m really curious to know what the language (and the compiler) does when it finds a comparison like this. And, of course, if it is a correct way to do something, or if I have to use something like strcmp().

EDIT
Wait wait.
Since someone haven’t understood what I really mean, I decided to explain in another way.

char x, y;
cout << "Put a character: ";
cin >> x;
cout << "Put another character: ";
cin >> y;

if (x == y)
    doSomething();

Of course, in the if brackets you can replace == with any other comparison operator.
What really I want to know is: how the character are considered in C/C++? When the compiler compares two characters, how does it know that ‘a’ is different than ‘b’? It refers to the ASCII table?

Answer 1

In C and C++, single character constants (and char variables) are integer values (in the mathematical sense, not in the sense of int values). The compiler compares them as integers when you use ==. You can also use the other integer comparison operators (<, <=, etc.) You can also add and subtract them. (For instance, a common idiom to change a digit character into its numerical value is c - '0'.)