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Uses of Header Files
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Uses
of header files
Header
files serve two kinds of purposes.
-
System header files declare
the interfaces to parts of the operating system. You include them in your
program to supply the definitions and declarations you need to invoke system
calls and libraries.
-
Your own header files contain
declarations for interfaces between the source files of your program. Each
time you have a group of related declarations and macro definitions all
or most of which are needed in several different source files, it is a
good idea to create a header file for them.
Including
a header file produces the same results in C compilation as copying the
header file into each source file that needs it. But such copying would
be time-consuming and error-prone. With a header file, the related declarations
appear in only one place. If they need to be changed, they can be changed
in one place, and programs that include the header file will automatically
use the new version when next recompiled. The header file eliminates the
labor of finding and changing all the copies as well as the risk that a
failure to find one copy will result in inconsistencies within a program.
The
usual convention is to give header files names that end with .h,
avoiding unusual characters in header file
names since they reduce portability.
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