| a computer program with any of several ancillary functions, usu. held resident in RAM for instant activation while one is using another program. |
TSR  (tē'ěs-är')  n. A program, such as a spell checker or calendar, that remains loaded in memory so that it may be quickly recalled while another program is running, as found in operating systems which do not allow multitasking. [t(erminate and) s(tay) r(esident).] |