Intel® C++ Compiler XE 13.1 User and Reference Guides
The IEEE Standard 754 specifies values and requirements for floating-point representation (such as base 2). The standard outlines requirements for two formats: basic and extended, and for two word-lengths within each format: single and double.
The Intel C/C++ Compiler supports the GCC decimal floating point feature and the following decimal floating types: _Decimal32, _Decimal64, and _Decimal128. This feature is supported for applications written in C only. These three decimal formats are defined in IEEE 754-2008 standard. See http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1312.pdf.