cppreference.com > C/C++ Pre-processor Commands C/C++ Pre-processor Commands Display all entries for C/C++ Pre-processor Commands on one page, or view entries individually:
#, ## | manipulate strings
#define | define variables
#error | display an error message
#if, #ifdef, #ifndef, #else, #elif, #endif | conditional operators
#include | insert the contents of another file
#line | set line and file information
#pragma | implementation specific command
#undef | used to undefine variables
Predefined preprocessor variables | miscellaneous preprocessor variables