Skills

TS Rs

Field	Programming
Went Obsolete	mid 90s
Made Obsolete By	Windows 95
Knowledge Assumed	DOS internals (if you wanted to call int 21h)
When useful	DOS like systems

TSR (terminate and stay resident) was a technique that allowed computer programs of the DOS era to be loaded into memory and be used later when some other DOS program was used. The typical TSR would take over some interrupt (e.g. keyboard) and perform its action (e.g. grab the screen and save it to some file) when an interrupt call met some predefined condition.