It's programming time!/C++/preprocessor directives

Here is the exciting list of preprocessor directives!

It does excite you, right? Yeah, me neither...but, well, they are used alot, so good for referencing.

Name	Action
#	Null directive specifying that no action be performed.
#define	Defines
#elif	Conditionally includes source text if the previous #if, #ifdef, #ifndef, or #elif test fails.
#else	Conditionally includes source text if the previous #if, #ifdef, #ifndef, or #elif test fails.
#endif	Ends conditional text.
#error	Defines text for a compile-time error message.
#if	Conditionally includes or suppresses portions of source code, depending on the result of a constant expression.
#ifdef	Conditionally includes source text if a macro name is defined.
#ifndef	Conditionally includes source text if a macro name is not defined.
#include	Inserts text from another source file.
#line	Supplies a line number for compiler messages.
#pragma	Specifies implementation-defined instructions to the compiler.
#undef	Removes a preprocessor macro definition.