Double-extended-precision

The C compiler produces code that uses IEEE double-extended-precision arithmetic. On implementations that do not produce IEEE double-extended-precision arithmetic, either for intermediate or final results, all results are computed with the precision implicit in their type.

ANSI C includes a new data type called long double, which maps to the IEEE extended-precision format. Extended-precision is a wider type than double. Doubles on the Intel386^(TM) microprocessor are 64 bits, long doubles are 80 bits. All arithmetic operations (+,-,*,/) work analogously. However, ANSI C does not require a long double to be wider than a double. On Intel^(TM) processors, complete support for long double is available.