Macros in C refers to the C preprocessor . cpp runs over your source code when you compile it, and feeds its output directly to the input of the actual C compiler.
cpp processes all of the #define and #undef, etc. constructs in your program. Macros, specifically, are defined using the syntax:
The #define directive has the following syntax:
#define identifier replacement-list newline
#define identifier ( identifier-list(opt) )
The #undef directive has the following syntax:
#undef identifier newline
macro is an identifier.