Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

IMPRECISE

This option determines the precision of floating-point results and the location at which floating-point interrupts are reported.

Read syntax diagramSkip visual syntax diagram   .-IMPRECISE---.
>>-+-NOIMPRECISE-+---------------------------------------------><
 

ABBREVIATIONS: IMP, NIMP

IMPRECISE
Precision of floating-point results might not be IEEE conforming and the location of floating-point interrupts might not be precise. The loss of precision is negligible for most applications. The location of interrupt might be close to the interruption point or might be far from the interruption point, perhaps in another block.

Use of this option produces smaller object code that runs faster. It is recommended for your production programs.

NOIMPRECISE
Precision of floating-point results is IEEE conforming and the precise location of floating-point interrupts is required. This option produces code that runs slower and is recommended only, if at all, during program development.

Although NOIMPRECISE does provide better floating-point error detection than IMPRECISE, the Windows operating system does not allow immediate detection of floating-point exceptions. If you have a statement in your program that is likely to raise a floating-point exception, you can avoid this detection problem by enclosing the statement, by itself, in a BEGIN block.

Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide