Shoutbox

A quick explanation of why it works:

In C, as in many programming languages, the char datatype is basically a number. Therefore, integer comparisons are possible, even without typecasts, and using %d in a printf is also perfectly valid.
As an example, take getchar(). It's signature is

code:

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int getchar(void);

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It gets a character from the keyboard (stdin), and returns it as unsigned. This leaves the negative values of int free for error codes.
Put simply:
0-255 is a valid character
<0 is an error.

Edit: Of course, once you've checked it's positive, you will need to typecast into a char. char is typically 8 bits, int 16/32 bits.