C examples for Preprocessor:Macro
C specifies five built-in predefined macro names. They are
__LINE__ __FILE__ __DATE__ __TIME__ __STDC__
The __LINE__ and __FILE__ macros contain the current line number and filename of the program when it is being compiled.
The __DATE__ macro contains a string of the form month/day/year when the source file is compiled into object code.
The __TIME__ macro contains the time in form of hour:minute:second at which the program was compiled.
If __STDC__ is defined as 1, then the compiler conforms to Standard C.
C99 also defines these two macros:
__STDC_HOSTED__ __STDC_VERSION__
__STDC_HOSTED__ is 1 for environments in which an operating system is present and 0 otherwise.
__STDC_VERSION__ will be at least 199901 and will be increased with each new version of C.