Science Fair Project Encyclopedia
DESQview was a text mode multitasking program 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 windows.
Quarterdeck originally developed a task switching product that allowed users to switch between tasks called DESQ. This product was not very popular, and the task switching market was primarily owned by Software Carousel. This product had limited windowing capabilities.
Quarterdeck revamped its product, bringing multitasking in, and adding TopView compatibility, this became DESQview.
DESQview was developed by Quarterdeck Office Systems which released it in July 1985, four months before Microsoft introduced the first version of Windows. DESQview 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 failed TopView, released in 1984, from which DESQview inherited the popup menu.
Under DESQview, well-behaved DOS programs could be run concurrently in resizable, overlapping windows (something the first version of Windows could not do). A simple hidable menu allowed cutting and pasting between programs. DESQview allowed simple editable macros as well. Quarterdeck also developed a set of optional utilties 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.
DESQview was not a full-fledged GUI operating system; it was a quasi-GUI shell that ran in real mode on top of DOS. Although it could be configured to run on an Intel 80286-based PC AT with two megabytes of memory, it really came into its own on Intel 80386 machines which were better at utilizing memory above DOS's limit of 640 KB. However, in either case, it ran in real mode rather than protected mode, meaning that a misbehaving program could still crash the system.
DESQview and QEMM
To make maximum use of extended memory on Intel 80386 processors, by transforming it into expanded memory and upper memory blocks (UMBs) accessible to DESQview and other real-mode programs, Quarterdeck developed a sophisticated memory manager. Owing to the foresight of its marketing manager, Quarterdeck marketed it as a separate product, QEMM-386 (Quarterdeck Expanded Memory Manager 386). It became more popular than DESQview itself, and sold steadily for many years, generating over $150 million in sales from 1987 through 1994. After the release of the Intel Pentium processor, the 386 in QEMM was dropped. The combination package of DESQview and QEMM-386 was called DESQview 386.
With the introduction of the 80386 the memory management features were enhanced again allowing the system to be shifted into protected mode but also allowing the addresses to be configured in a virtual 8086 mode so that the extended memory could be mapped into addressing frames and accessible to real-mode programs such as MS-DOS. This allowed a 386 to implement the LIM (Lotus, Intel, Microsoft) EMS (expanded memory specification).
DESQview was able to use QEMM's features far beyond just the LIM EMS API, mapping most of the "conventional" address space (below 640 KB) into multiple extended memory blocks such that each could execute transparently during its context. The main copy of DOS and any device and networking drivers had to be loaded before DESQview. The resulting space was the largest single program that could run, but DESQview under QEMM could run as many instances of those programs as the EMS would allow. So an 8-MB system could generally have a dozen full-sized MS-DOS programs running concurrently; a 16-MB system could run over twenty, and so on.
DESQview was noteworthy in that it supported all common DOS-compatible programs and achieved a degree of performance and stability that was remarkable, given the constraints of its host operating system. It also had a clever interface that was generally unobtrusive while being quickly available and very easy to learn.
All normal PCs include a keyboard with three "shift" or "modifier" keys: Control, Alt, and the normal Shift keys. These keys are normally held down in combination with other keys. DESQview, by default, monitored the Alt key for isolated presses (not in combination). Pressing the Alt key by itself would bring up the DESQview menu allowing access to the program's features: start new tasks, switch among them, mark text on the screen, paste text as input into the current task, resize or move the text windows, configure new menu items, etc. In addition a Shift+Alt combination would cause DESQview to learn a set of keys as a macro. This allowed DESQview to run other programs without interfering with any of the "keybindings" they might be using.
DESQview was critically acclaimed and won many fans, but it never met with mass appeal, despite Quarterdeck's sustained efforts to win people over. Reportedly it intrigued many people at Microsoft, including Bill Gates, who by some accounts based his first version of Windows on DESQview and two other early GUIs, Visi On and GEM.
In one area, however, DESQview was a lasting success: many multiuser bulletin board systems were based on it, thanks to its modest hardware requirements, robust multitasking, and superlative handling of multiple communication ports. Most free or inexpensive BBS software of the time ran as a single-node , single-tasking DOS program. Normally, only one copy of the BBS software could run at once, limiting the host PC to running one node. DESQview allowed multiple copies of these single-task programs to run at once on the same computer, allowing anyone with even unimpressive hardware to run a large, powerful, multiuser BBS out of their home.
Decline of DESQview
DESQview did not provide a graphical user interface (GUI). While Quarterdeck did provide suites of programming libraries and utilities to support the development of software to use its features these never became widely popular. (DESQview's ability to run most software with no modification and the cost of "run-time" licenses, combined with the costs of the development suites themselves made this an unreasonable combination for commercial shrink-wrapped software publishers and vendors).
Microsoft released Microsoft Windows version 3.0 with its own memory management and multitasking features. While DESQview was far faster, smaller, and more stable it was more expensive and didn't include support for the graphical features of MS Windows. Microsoft exerted considerable pressure on ISVs (independent software vendors) to release GUI software for Windows and hardware wholesalers (among others) to bundle MS Windows with MS-DOS on all systems that they sold (providing a broader market for the applications developed by the ISVs).
The decline of QEMM started with the bundling of a memory manager in Digital Research's DR-DOS 5.0, released in 1990. To catch on, Microsoft included its own EMM386 in MS-DOS 5.0, while previously the memory management functionality was only available with Windows. QEMM could still be used instead, notably with Windows 3.1, but it only provided incremental benefits. Sales of QEMM declined. In August 1994, after three quarters of losses, the company fired 25% of employees and the CEO, president, and founder Terry Myers resigned.
Quarterdeck eventually also released a product named DESQview/X, which was an X server running under MS-DOS and DESQview and thus provided a GUI to which X software (mostly UNIX) could be ported. However, by the time this was release there were far too many applications available for MS Windows, software for UNIX was generally free (non-commercial) or very expensive, and PCs in general were still under-powered compared to graphical UNIX workstations. Linux was also becoming available, and eventually provided a robust operating system, X server, and a UNIX-compatible API. In other words DESQview/X was in far too small a niche.
DVX itself could serve DOS and Windows 3.0 programs across the network as X programs, which made it useful for those who wished to run DOS and Windows programs from their Unix workstations.
DESQview after X
DESQview development continued in parallel with DESQview/X. After ceasing development on DESQview/X, another version of DESQview was released. QEMM was still developed after the discontinuation of DESQview, and a version compatible with Windows 98 was released.
Free public release
The DESQview packages have been available for download on the Internet for a few years on at least one stable site (listed below) with no trace of complaint, however neither the host site CharterSoft nor Symantec's corporate counsel will clarify copyright status on direct request. Claims that the software is "public domain" are unsubstantiated and appear to be based solely on an editor statement at Slashdot.
- DESQview download
- Slashdot article of public domain release of DESQview
- DESQview FAQ
- Screen snapshots of DESQview/X
- OpenDV/X: an OpenSource project to recreate DESQview/X for DOS
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details