The preprocessor directives are the lines that are included in a program which begins with the # and it is different from the typical source code.
They are invoked by the compiler to process the programs before compilation. The preprocessor directive is placed at the top of the source code in a separate line beginning with the character # and followed by a directive name.
The preprocessor directive statement cannot be with semi colon. Some of the examples of preprocessor directives are #define, #include, #indef, etc.
