DESQview

DESQview was a text mode multitasking program 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. DESQview was released in July 1985, four months before Microsoft introduced the first version of Windows. It was widely thought to be the first program to bring multitasking and windowing capabilities to DOS, but in fact there was a predecessor, IBM's TopView, released in 1984, from which DESQview inherited the popup menu.