C Language – The Preprocessor

 The Preprocessor, Preprocessor directives, Macros, #define identifier string, Simple macro substitution, Macros as arguments, Nesting of macros, Undefining a macro and File inclusion. The Preprocessor A unique feature of c language is the preprocessor. A program can use the tools provided by preprocessor to make his program easy to read, modify, portable and more efficient. Preprocessor is a program that processes the code before it passes through the compiler. It operates under the control of preprocessor command lines and directives. Preprocessor directives are placed in the source program before the main line before the source code passes through the compiler it is examined by the preprocessor for any preprocessor directives. If there is any appropriate actions are taken then the source program is handed over to the compiler. Preprocessor directives follow the special syntax rules and begin with the symbol #bin column1 and do not require any semicolon at the end. A set of commonly used preprocessor
The preprocessor directives can be divided into three categories 1. Macro substitution division 2. File inclusion division 3. Compiler control division