=====Preprocessor=====

The preprocessor runs before the compilation begins. The result of preprocessing is single file which is then passed to the actual compiler.

====Directives====

The preprocessing directives control the behavior of the preprocessor. Each directive occupies one line and has the following things included in it:

  * ''#'' character
  * preprocessing instruction (one of ''define'', ''undef'', ''include'', ''if'', ''ifdef'', ''ifndef'', ''else'', ''elif'', ''endif'', ''line'', ''error'', ''pragma'')
  * arguments (depends on the instruction)

====Capabilities====

The preprocessor has the source file translation capabilities:

  * [[conditional | conditionally]] include of parts of source file (controlled by directives ''#if'', ''#ifdef'', ''#ifndef'', ''#else'', ''#elif'' and ''#endif'')
  * [[replace]] text macros while possibly concatenating or quoting identifiers (controlled by directives ''#define'' and ''#undef'', and operators ''#'' and ''##'')
  * [[include]] other files (controlled by directive ''#include'')
  * cause a [[warning]] (controlled by directive ''#warning'')
  * cause an [[error]] (controlled by directive ''#error'')

The following aspects of the preprocessor can be controlled:
  * [[impl | implementation defined]] behavior (controlled by directives ''#pragma'')
  * [[line | file name and line information]] available to the preprocessor (controlled by directives ''#line'')