When writing your C program, you can include
files in two ways.
The first way is to surround the file you want to include with the
angled brackets < and >.
This method of inclusion tells the preprocessor to look for the file
in the predefined default location.
This predefined default location is often an INCLUDE environment
variable that denotes the path to your include files.
For instance, given the INCLUDE variable
using the #include version of file inclusion, the compiler first
directory for the specified file. If the file is not found there,
the compiler then checks the
S:\SOURCE\HEADERS directory. If the file is still not found, the
preprocessor checks the current directory.
The second way to include files is to surround the file you want to
include with double quotation marks. This method of inclusion tells
the preprocessor to look for the file in the current directory
first, then look for it in the predefined locations you have set up.
Using the #include file version of file inclusion and applying it to
the preceding example, the preprocessor first checks the current
directory for the specified file. If the file is not found in the
current directory, the C:COMPILERINCLUDE directory is searched. If
the file is still not found, the preprocessor checks the
The #include method of file inclusion is often used to include
standard headers such as stdio.h or
This is because these headers are rarely (if ever) modified, and
they should always be read from your compilerís standard include
The #include file method of file inclusion is often used to include
nonstandard header files that you have created for use in your
program. This is because these headers are often modified in the
current directory, and you will want the preprocessor to use your
newly modified version of the header rather than the older,