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.
[glossary]