test for C95 compatibility #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199409L /* C95 compatible source code. */ #elif defined() /* C89 compatible source code. */ #endif C99 In March 2000, ANSI adopted the ISO/IEC 9899:1999 standard. This standard is commonly referred to as C99. Some notable additions to the previous standard include: New built-in data types: long long, _Bool, _Complex, and _Imaginary Several new core language features, including static array indices, designated initializers, compound literals, variable-length arrays, flexible array members, variadic macros, and restrict keyword Several new library headers, including stdint.h, <tgmath.h>, fenv.h, <complex.h> Improved compatibility with several C++ features, including inline functions, single-line comments with //, mixing declarations and code, and universal character names in identifiers Removed several dangerous C89 language features such as implicit function declarations and implicit int Three technical corrigenda were published by ISO for C99: ISO/IEC 9899:1999/Cor 1:2001(E) ISO/IEC 9899:1999/Cor 2:2004(E) ISO/IEC 9899:1999/Cor 3:2007(E), notable for deprecating the standard library function gets This standard has been withdrawn by both ANSI/INCITS and ISO/IEC in favour of C11. C11 C11 was officially ratified and published on December 8, 2011. Notable features include improved Unicode support, type-generic expressions using the new _Generic keyword, a cross-platform multi-threading API (threads.h), and atomic types support in both core language and the library (stdatomic.h). One technical corrigendum has been published by ISO for C11: ISO/IEC 9899:2011/Cor 1:2012 C17 , "C17" is the current standard for the C programming language. C17 addresses defects in C11 without introducing new language features. C2x C2x is an informal name for the next (after C17) major C language standard revision. Other related ISO publications As part of the standardization process, ISO/IEC also publishes technical reports and specifications related to the C language: ISO/IEC TR 19769:2004, on library extensions to support Unicode transformation formats, integrated into C11 ISO/IEC TR 24731-1:2007, on library extensions to support bounds-checked interfaces, integrated into C11 ISO/IEC TR 18037:2008, on embedded C extensions ISO/IEC TR 24732:2009, on decimal floating point arithmetic, superseded by ISO/IEC TS 18661-2:2015 ISO/IEC TR 24747:2009, on special mathematical functions, ISO/IEC TR 24731-2:2010, on library extensions to support dynamic allocation functions ISO/IEC TS 17961:2013, on secure coding in C ISO/IEC TS 18661-1:2014, on IEC 60559:2011-compatible binary floating-point arithmetic ISO/IEC TS 18661-2:2015, on IEC 60559:2011-compatible decimal floating point arithmetic ISO/IEC TS 18661-3:2015, on IEC 60559:2011-compatible interchange and extended floating-point types ISO/IEC TS 18661-4:2015, on IEC 60559:2011-compatible supplementary functions More technical specifications are in