Rational Developer for System z
Enterprise PL/I for z/OS, Version 3.8, Language Reference Manual

UNDERFLOW condition

Status
UNDERFLOW is enabled throughout the program, except within the scope of the NOUNDERFLOW condition prefix.
Result
The invalid floating-point value is set to 0 except for IEEE floating-point on z/OS when the result is undefined.
Cause and syntax
The UNDERFLOW computational condition is raised when the magnitude of a floating-point number is smaller than the minimum allowed. save UNDERFLOW is not raised when equal numbers are subtracted (often called significance error).

The expression X(-Y) (where Y>0) can be evaluated by taking the reciprocal of XY; hence, the OVERFLOW condition might be raised instead of the UNDERFLOW condition.

Read syntax diagramSkip visual syntax diagram>>-UNDERFLOW---------------------------------------------------><
 
Abbreviation
UFL
Implicit action
Unless the exception is raised while evaluating an IEEE floating-point expression (in either binary or decimal) on z/OS, a message is printed, and execution continues from the point at which the condition was raised; if raised while evaluating an IEEE floating-point exception on z/OS, a message is printed and the ERROR condition is raised.
Normal return
Unless the exception is raised while evaluating an IEEE floating-point expression (in either binary or decimal) on z/OS, control returns to the point immediately following the point at which the condition was raised; if raised while evaluating an IEEE floating-point exception on z/OS, the ERROR condition is raised.
Condition code
330

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