1. [primarily MS-DOS] Said of software conforming to system interface guidelines and standards. Well-behaved software uses the operating system to do chores such as keyboard input, allocating memory and drawing graphics. Oppose ill-behaved. 2. Software that does its job quietly and without counterintuitive effects. Esp. said of software having an interface spec sufficiently simple and well-defined that it can be used as a tool by other software. See cat. 3. Said of an algorithm that doesn't crash or blow up, even when given pathological input. Implies that the stability of the algorithm is intrinsic, which makes this somewhat different from bulletproof.