Everything before standardization is generally called “K&R C”, after the famous book, with Dennis Ritchie, the inventor of the C language, as one of the authors. This was “the C language” from 1972-1989.The first C standard was released 1989 nationally in USA, by their national standard institute ANSI. This release is called C89 or ANSI-C. From 1989-1990 this was “the C language”.The year after, the American standard was accepted internationally and published by ISO (ISO 9899:1990). This release is called C90. Technically, it is the same standard as C89/ANSI-C. Formally, it replaced C89/ANSI-C, making them obsolete. From 1990-1999, C90 was “the C language”.Please note that since 1989, ANSI haven’t had anything to do with the C language. Programmers still speaking about “ANSI C” generally haven’t got a clue about what it means. ISO “owns” the C language, through the standard ISO 9899.In 1999, the C standard was revised, lots of things changed (ISO 9899:1999). This version of the standard is called C99. From 1999-2011, this was “the C language”. Most C compilers still follow this version.In 2011, the C standard was again changed (ISO 9899:2011). This version is called C11. It is currently the definition of “the C language”.
gcc – What is the difference between C, C99, ANSI C and GNU C? A general confusion regarding the various versions of C – Stack Overflow