Preprocessor     An Overview of Preprocessor Directives
 Predefined       Macros Built in to the Preprocessor
 #include         File Inclusion
 #define          Macro Definition
 #undef           Remove a Macro Definition
 #if              Conditional Compilation by Expression
 #ifdef           Conditional Compilation by Macro Definition
 #ifndef          Conditional Compilation by Lack of Macro Definition
 #elif            Abbreviation for #else and #if
 #else            False Path for Conditional Compilation Tests
 #endif           Marks the End of Conditional Compilation Scope
 #line            Line Control
 defined          defined Preprocessor Operator
 #pragma          Implementation-Defined Preprocessor Directive