# Revision history [back]

From the man page:

man gcc
....
gnu89
GNU dialect of ISO C90 (including some C99 features). This is the default for C code.

gnu99
gnu9x
GNU dialect of ISO C99.  When ISO C99 is fully implemented in GCC, this will become the default.  The name gnu9x is deprecated.

gnu11
gnu1x
GNU dialect of ISO C11.  Support is incomplete and experimental.  The name gnu1x is deprecated.

c++98
The 1998 ISO C++ standard plus amendments. Same as -ansi for C++ code.

gnu++98
GNU dialect of -std=c++98.  This is the default for C++ code.
....


You really should read the man page. It has most of the answers.