#include
This is called File Inclusion Directive, it causes one file to be included in another. It simply causes the entire content of the filename to be inserted into the source code. It is common for the file included to have a .h exyension(header File)

Actually There are two ways to write #include statement. These are
  • #include "filename"
  • #include <filename>


#include "abc.h" This command would look for the file abc.h in the current directory as well as the specified list of directories as mentioned in the include search path that might have been set.

#include <abc.h> This Command would look for the file abc.h in the specified list of directories only ( include directory)