The #error and #pragma Preprecessor directives

I read what's written about then in my C++ text book ( Deitel # Deitel 3rd edition ), but still I couldn't understand them...
Can explane them for me, please... Or give me an example...
Thanks in advace...

what's there not to understand? #error halts compilation. the end. as for #pragma, it does nothing in vanilla ansi C/C++, but various compilers use it as a way to add various features. consult your compiler's documentation for info about #pragmas you can use.

#error ends compilation to report an error.
#pragma performs compiler specific tasks.

Thanks alot, I'll check the help file in my compiler...