DESQview was a text mode multitasking operating environment developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. Running on top of DOS, it allowed users to run multiple DOS programs concurrently in multiple windows.
Read more about DESQview: Desq, DESQview, DESQview and QEMM, DESQview Usage, Decline of DESQview, Public Release Questions