DESQview

DESQview (DV) is a text modemultitaskingoperating environment released by Quarterdeck Office Systems in 1985 which enjoyed modest popularity in the late 1980s and early 1990s. Running on top of DOS, it allows users to run multiple programs concurrently in multiple windows.

DESQview/X (DVX), released in 1992, had a graphical user interface.