ill-behaved

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. 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 IBM PC/MS-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}. Oppose {well-behaved},
   compare {PC-ism}.  See {mess-dos}.