Preprocessor Directives

Preprocessor directives must be the first non-whitespace text specified on a line. All directives are prefixed with the pound or number-sign character ('#'). For example:

#pragma PRINT
#include <stdio.h>
#define DEBUG 1

Whitespace is allowed before and after the number-sign ('#'). A number-sign ('#') that appears alone on a line is interpreted as a null preprocessor directive. For example:

# define myfavnum 45
#
   #    include <stdio.h>

The entire proprocessor directive must be contained in a single source line. Line continuations, backslash ('\') followed by a new-line character, may be used in preprocessor directives since these are removed by the preprocessor. For example:

#define mycode                      \ 
        {                           \ 
        volatile unsigned char i;   \ 
        for (i=0; i<100; i++);      \ 
        }

The number-sign ('#') and the preprocessor directive must be explicitly specified and may not come from a macro expansion. For example:

#define mydef #define otherdef 16

mydef

In this case, mydef is expanded to define otherdef 16 since # is interpreted as a stringize operator. This expansion is processed by the compiler and a syntax error is generated.

The following table lists the preprocessor directives and gives a brief description of each.