DESQview

DESQview (DV) 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, and was a direct precursor to the graphical user interface of the Microsoft Windows line which was introduced in 1985.

Desq

Quarterdeck's predecessor to DESQview was a task switching product called Desq (shipped late April or May 1984) which allowed users to switch between running programs. Quarterdeck revamped its package, bringing multitasking in, and adding TopView compatibility.

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, shipped March 1985, from which DESQview inherited the pop-up menu.

Under DESQview, well-behaved DOS programs could be run concurrently in resizable, overlapping windows (something the first version of MS Windows could not do). A simple hidable menu allowed cutting and pasting between programs. DESQview provided support for simple editable macros as well. Quarterdeck also developed a set of optional utilities for DESQview, including a notepad and dialer. Later versions allowed graphics mode programs to be loaded as well, but only run in full screen mode.