1. [numerical analysis] Said of an algorithm or
computational method that tends to blow up because of
accumulated roundoff error or poor convergence properties.

2. Software that bypasses the defined operating system
interfaces to do things (like screen, keyboard, and disk I/O)
itself, often in a way that depends on the hardware of the
machine it is running on or which is nonportable or
incompatible with other pieces of software.

In the IBM PC/mess-dos world, there is a folk theorem
(nearly true) to the effect that (owing to gross inadequacies
and performance penalties in the OS interface) all interesting
applications are ill-behaved.

See also bare metal. Opposite: well-behaved, compare
PC-ism.

[Jargon File]