The C-preprocessors are specified with # symbol.

The #include directive tells the preprocessor to grab the text of a file and place it directly into the current file and are statements are typically placed at the top of a program.

The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control.

With the #include, if the filename is enclosed within angle brackets, the file is searched for in the standard compiler include paths.