Before the standad

1978
The C Programming Language 1st ed. (Kernigham & Ritchie) “K&R C”

Standard Revisions

Year C Standard Informal name
1989 ANSI X3.159-1989 ANSI C, C89
1990 ISO/IEC 9899:1990 C90
1995 ISO/IEC 9899/AMD1:1995 C95, Amendment 1
2000 ISO/IEC 9899/1999 C99
2011 ISO/IEC 9899:20001 C11 (C1X)

Note: C90 is equivalent to C89

Major features per revision

K&R C

  • long int
  • unsigned int
  • compound += operators instead of =+
  • I/O library

ANSI C

  • __STDC__
  • Function prototypes
  • preprocessor: token concatenation ##, string creation #elif, #pragma
  • trigraph sequences ??
  • new keyworkds: void, const, volatile, signed, enum
  • new escape sequences \
  • constant suffixes U L, F L
  • wide char strings
  • signed/unsigned
  • void * instead of char *`
  • enumerations
  • type qualifiers (const)
  • type properties in
  • assignment operators single token; old =+ operators gone
  • unary +
  • pointer to function use without *
  • structure copy (assignment, passed to or returned from functions)
  • address of array returns pointer to array
  • size_t, ptrdiff_t <stddef.h>
  • automatic structures, unions and arrays initialization
  • switch for any integral type
  • Standard Library

C95

  • __STDC_VERSION__ == 199409L
  • digraphs for []{}

  • extended character sets support

  • Standard Library:
    • <iso646.h>
    • EILSEQ in ‘'
    • changes in ‘ '

C99

  • __STDC_VERSION__ == 199901L
  • inline functions
  • intermingled declarations
  • long long int, boolean, complex
  • variable-length arrays
  • flexible array members
  • one-line comments //
  • improved IEEE floating point support
  • designated initializers
  • compound literals
  • variadic macros
  • restrict qualification

  • universal character names

  • Standar Library:std lib
    • snprintf
    • <stdbool.h> <complex.h> <tgmath.h> <inttypes.h>

C11

  • __STDC_VERSION__ == 201112L
  • alignment specification _Alignas, _Alignof, aligned_alloc
  • _Noreturn
  • _Generic
  • _Thread_local
  • Unicode support chart16_t, char32_t
  • anonymous structures and unions

  • static assertions

  • Standard Library
    • <stdalign.h> <threads.h> <uchar.h>
    • gets_s
    • bound-checking interfaces
    • exclusive create and open mode “x”
    • quick_exit
    • complex variable macros
    • floating point macros