The GNU C Reference Manual
www.gnu.org › software › gnu-c-manualCompiler Collection (GCC). Specifically, this manual aims to document: The 1989 ANSI C standard, commonly known as “C89” The 1999 ISO C standard, commonly known as “C99”, to the extent that C99 is implemented by GCC The current state of GNU extensions to standard C This manual describes C89 as its baseline.