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
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 processors, complete support for
long double is available.