► #define and #undef - Used for defining and undefining MACROS.

► #error - Used for Debugging

► #include - Used for combining source code files

► #if, #else, #elseif, and #endif - Used for conditional compilation similar to if - else statment.

► #ifdef and #ifndef - Conditional Compilation on basis of #define and #undef

► #line - Controls the program line and file macros.

► #pragma - Used for giving compiler instruction. Highly specific to the compiler being used.

► # and ## - Operators used for stringize and concating operation respectively.