You must know C++11, but have you noticed C11?

Previous C++ standard is C++03 (2003); previous C std is C99.They are not released together, but they did this time as  a combo of C11 and C++11.

__STDC_VERSION__ == 201112L

C11 (formerly C1X) is an informal name for ISO/IEC 9899:2011  (see wiki)

http://en.wikipedia.org/wiki/C11_%28C_standard_revision%29

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Changes from C99

The standard includes several changes to the C99 language and library specifications, such as:^[8]

• Alignment specification (_Alignas specifier, alignof operator, aligned_alloc function, <stdalign.h> header file)
• The _Noreturn function specifier
• Type-generic expressions using the _Generic keyword. For example, the following macro cbrt(x) translates to cbrtl(x), cbrt(x) or cbrtf(x) depending on the type of x:

#define cbrt(X) _Generic((X), long double: cbrtl, \
                              default: cbrt, \
                              float: cbrtf)(X)

• Multithreading support (_Thread_local storage-class specifier, <threads.h> header including thread creation/management functions, mutex, condition variable and thread-specific storage functionality, as well as the _Atomic type qualifier and <stdatomic.h> for uninterruptible object access).
• Improved Unicode support based on the C Unicode Technical Report ISO/IEC TR 19769:2004 (char16_t and char32_t types for storing UTF-16/UTF-32 encoded data, including conversion functions in <uchar.h> and the corresponding u and U string literal prefixes, as well as the u8 prefix for UTF-8 encoded literals).^[9]
• Removal of the gets() function, deprecated in the previous C language standard revision, ISO/IEC 9899:1999/Cor.3:2007(E), in favor of a new safe alternative, gets_s.
• Bounds-checking interfaces (Annex K).^[10]
• Analyzability features (Annex L).
• More macros for querying the characteristics of floating point types, concerning subnormal floating point numbers and the number of decimal digits the type is able to store.
• Anonymous structures and unions, useful when unions and structures are nested, e.g. in struct T { int tag; union { float x; int n; }; };.
• Static assertions, which are evaluated during translation at a later phase than #if and #error, when types are understood by the translator.
• An exclusive create-and-open mode ("…x") for fopen. This behaves like O_CREAT|O_EXCL in POSIX, which is commonly used for lock files.
• The quick_exit function as a third way to terminate a program, intended to do at least minimal deinitialization if termination with exit fails.^[11]
• Macros for the construction of complex values (partly because real + imaginary*I might not yield the expected value if imaginary is infinite or NaN).^[12]

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There is little new features compared with C99, that is why it is less reported than C++11.

C99, new features including:

• Variable length arrays
• Designated initializers
• Type-generic math library
• New datatypes: long long, _Complex, _Bool
• restrict pointers
• Intermingled declarations of variables
• Inline functions
• One-line comments that begin with //

Introduction of new features of C11 can be found here:

http://blog.smartbear.com/software-quality/bid/173187/C11-A-New-C-Standard-Aiming-at-Safer-Programming

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GCC 4.7 is a milestone for C++11 and  C11 support,  you can use

gcc -std=c11

g++ -std=c++11

C11 support status by GNU GCC can be found here.

http://gcc.gnu.org/wiki/C11Status

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#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <stddef.h> //size_t
#include <locale.h>
#include <limits.h>  // double is not supported
#include <float.h>  // isnan()  isinf()
// for a full list of std c headers:

// C99
#include <stdarg.h>  //va_list
#include <stdinttypes.h>
#include <complex.h>  //complex number
#include <tgmath.h>  //type generic math
#include <fenv.h>   // float exception
//C99 adopted into C++11
#include <stdbool.h>  // standarization into C++11
#include <stdint.h>  // standarization into C++11
#include <wctype.h>

//new headers from C11
//#include <uchar.h>  // not supported yet by mingw32 4.7
//#include <stdatomic.h>
//#include <stdalign.h>
//#include <stdnoreturn.h>
//#include <threads.h>