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. Especially 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. [Jargon File]