C Standard Conformance
The Intel(R) C++ Compiler for Linux* or OS X* version 10.x, 11.x, 12.x, 13.x, 14.0 & 15.0 or Intel Parallel Composer 2011 conforms to the ANSI/ISO standard ISO/IEC 9899:1999 for C language.
The Intel(R) C++ Compiler for Windows version 10.x, 11.x, 12.x, 13.x, 14.0 & 15.0 or Intel Parallel Composer 2011 conforms to the ANSI/ISO standard ISO/IEC 9899:1990 for C language by default, but comforms to ANSI/ISO standard ISO/IEC 9899:1999 under /Qstd=c99 switch.
Please see "Language Conformance" section in the User's Guide for the list of C99 features supported by Intel C++ Compiler.
C++ Standard Conformance
The Intel® C++ Compiler 10.x, 11.x, 12.x, 13.0, 14.0 & 15.0 or Intel Parallel Composer 2011 conforms to the ANSI/ISO standard ISO/IEC 14882:1998 for C++ language, with the following exception:
The export keyword for templates is supported in Intel® C++ Compiler for Linux* 8.1 to 12.x with "-export" option. It is supported in the Intel® C++ Compiler for OS X* till 12.x with "-export" option. The support is deprecated in 13.0 and 14.0; it is removed in 15.0.
But the export keyword for templates is not supported in the Intel® C++ Compiler for Windows or the Intel Parallel Composer.
For more information on C/C++ conformance, refer to the User's Guide. For information about the ANSI/ISO C/C++ language standards, please visit http://www.ansi.org/.† 
† This link will take you off of the Intel Web site. Intel does not control the content of the destination Web Site
OpenMP* conformance
- The Intel(R) C++ Compiler 15.0 supports most features in OpenMP* 4.0 API specification. Please see Release Notes "Updated Support for Upcoming OpenMP* features added in Intel® C++ Compiler 15.0" for detail information.
- The Intel(R) C++ Compiler 14.0 adds support for some OpenMP* 4.0 Public Review Release Candidate 2 specifications. See Release Notes's section "Updated Support for Upcoming OpenMP* features added in Composer XE 2013 SP1" for detail information.
- The Intel(R) C++ Compiler 12.1 and 13.0 conform to the OpenMP* 3.1 standard.
- The Intel(R) C++ Compiler 11.x and 12.0 conform to the OpenMP* 3.0 standard.
- The Intel(R) C++ Compiler 10.x and 9.1 conform to the OpenMP* 2.5 standard.
References:
C99 Support in Intel(R) C++ Compiler
C++11 Features Supported by Intel(R) C++ Compiler