XL C/C++ supports single-precision floating-point numbers with an approximate range of 10-38 to 10+38, and about 7 decimal digits of precision; and double-precision floating-point numbers with an approximate range of 10-308 to 10+308 and precision of about 16 decimal digits.
The following sections provide reference information, portability considerations, and suggested procedures for using compiler options to manage floating-point operations: