Q.What is C processor?

The C preprocessor is a program that runs before the compiler. It scans the source file for lines that begin with a hash symbol #, called preprocessor directives, and carries out the instructions they contain, producing an expanded source file that is then compiled.

The two most important directives are:

• #include - inserts the contents of another file into the program. It has two forms: #include <file name> searches the standard system directories (used for library headers such as stdio.h), while #include "file name" also searches the current directory (used for the programmer's own files). One included file may include others, but a file cannot include itself. …