ill-behaved

adj. 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. [obs.] Software that bypasses the defined OS
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
MS-DOS world, there was a folk theorem (nearly true) to the effect that
(owing to gross inadequacies and performance penalties in the OS interface)
all interesting applications were ill-behaved. See also bare metal. Oppose
well-behaved. See also mess-dos. 3. In modern usage, a program is called
ill-behaved if it uses interfaces to the OS or other programs that are
private, undocumented, or grossly non-portable. Another way to be
ill-behaved is to use headers or files that are theoretically private to
another application.

