C preprocessor

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C preprocessor
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The C preprocessor (cpp) is the preprocessor for the C programming language. In many C implementations, it is a separate program invoked by the compiler as the first part of translation. The preprocessor handles directives for source file inclusion (#include), macro definitions (#define), and conditional inclusion (#if). The language of preprocessor directives is agnostic to the grammar of C, so the C preprocessor can also be used independently to process other types of files.
The transformations it makes on its input form the first four of C's so-called Phases of Translation. Though an implementation may choose to perform some or all phases simultaneously, it must behave as if it performed them one-by-one in order.
Contents
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1 Phases
2 Including files
3 Conditional compilation
4 Macro definition and expansion
4.1 Standard predefined positioning macros
4.2 Precedence
4.3 Multiple lines
4.4 Multiple evaluation of side effects
4.5 Token concatenation
4.6 Semicolons
4.6.1 Multiple statements
4.7 Quoting macro arguments
4.7.1 Indirectly quoting macro arguments
4.8 Variadic macros
4.9 X-Macros
4.10 Compiler-specific predefined macros
5 User-defined compilation errors and warnings
6 Compiler-specific preprocessor features
7 As a general-purpose preprocessor
8 See also
9 References
10 External links
[edit] Phases
The following are the first four (of eight) phases of translation specified in the C Standard:
Trigraph Replacement - The preprocessor replaces trigraph sequences with the characters they represent.
Line Splicing - Physical source lines that are continued with escaped newline sequences are spliced to form logical lines.
Tokenization - The preprocessor breaks the result into preprocessing tokens and whitespace. It replaces comments with whitespace.
Macro Expansion and Directive