Within the set of numbers REXX understands, it is useful to distinguish the subset defined as whole numbers. A whole number in REXX is a number that has a decimal part that is all zeros (or that has no decimal part). In addition, it must be possible to express its integer part simply as digits within the precision set by the NUMERIC DIGITS instruction. REXX would express larger numbers in exponential notation, after rounding, and, therefore, these could no longer be safely described or used as whole numbers.