Topic       : C-Language Documentation
Author      : John Kormylo
Version     : C.HYP 1.0
Subject     : Documentation/C-Language
Nodes       : 233
Index Size  : 6362
HCP-Version : 3
Compiled on : Atari
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@lang       : en
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View Ref-File[ Preprocessor ]

The preprocessor (CPP.TTP) performs symbolic substitution and editing
on the C source code before it is turned over to the compiler
(creating file *.I which is subsequently deleted).

Preprocessor directives are line oriented, and always start with '#'
in the first column.  The backslash '\' character can be used as the
last character in a line to continue on the next line.

The most common directives are:

#include - insert code from a header file.
#define  - create a macro.
#undef   - remove a macro.
#pragma  - see #pragma warn.

Condition compilation is often used in header files to prevent
duplicate definitions.  It is also used to make source code portable
between different compilers, or to create a special DEBUG version of
the program, or to deactivate obsolete code.

#if  #ifdef  #ifndef  #else  #elif  #endif

#line    - resume compilation at a specific line number.
#error   - stop compilation and display message.

Note: One can insert blanks between the '#' and the directive name in
      order to achieve a more structured appearance.

See also Predefined Macros.