Guarding Header Files
The C Preprocessor
- removes whitespace
- removes comments
- processes #defines
- includes the files that are #included
- guards header files -
keeps header files from being placed
into a program's code multiple times.
Preprocessor Directives Used for Guarding a Header File
In our fraction.h example, notice that the file was guarded. The two
preprocesssor directives (#ifndef & #define) occur near the beginning
of the file and the preprocessor directive, #endif, occurs at the end
of the file.
#ifndef _fraction_h /* if fraction.h hasn't already been defined */
#define _fraction_h /* then define it as the following ... */
/* everything between the #define and the
#endif will be considered _fraction_h The
<code of the underscore which replaces the dot, is
header file> necessary since the preprocessor can't
handle dots well. The underscore before
the filename is traditional */
#endif
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Sunday, 20-Nov-2005 18:07:37 EST