MS-DOS 4.0 was a multitasking release of MS-DOS developed by Microsoft based on MS-DOS 2.0. Lack of interest from OEMs, particularly IBM (who previously gave Microsoft multitasking code on IBM PC DOS included with TopView), led to it being released only in a scaled-back form. It is sometimes referred to as European MS-DOS 4.0, as it was primarily used there. It should not be confused with PC DOS 4.00 or
MS-DOS 4.01
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
and later, which did not contain the multi-tasking features.
History
Apricot Computers pre-announced "MS-DOS 4.0" in early 1986, and Microsoft demonstrated it in September of that year at a Paris trade show. However, only a few European OEMs, such as SMT Goupil and
International Computers Limited
International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that operated from 1968 until 2002. It was formed through a merger of International Computers and Tabulators (ICT), English Ele ...
(ICL), actually licensed releases of the software. In particular, IBM declined the product, concentrating instead on improvements to MS-DOS 3.x and their new joint development with Microsoft to produce OS/2.
As a result, the project was scaled back, and only those features promised to particular OEMs were delivered. In September 1987, a version of multi-tasking MS-DOS 4.1 was reported to be developed for the ICL DRS Professional Workstation (PWS). No further releases were made once the contracts had been fulfilled.
In July 1988, IBM announced " IBM DOS 4.0", an unrelated product continuing from DOS 3.3 and 3.4, leading to initial conjecture that Microsoft might release it under a different version number. However, Microsoft eventually released it as "MS-DOS 4.0", with a
MS-DOS 4.01
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
following quickly to fix issues many had reported.
Features
As well as minor improvements such as support for the New Executable file format, the key feature of the release was its support for preemptive multitasking. This did not use the
protected mode
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as virtual memory, paging and safe multi-tasking d ...
available on
80386
The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsinterprocess communication via pipes and shared memory. This limited form of multitasking was considered to be more useful in a server rather than workstation environment, particularly coupled with MS-Net 2.0, which was released simultaneously.
Other limitations of MS-DOS 3.0 remained, including the inability to use memory above 640 KB, and this contributed to the product's lack of adoption, particularly in light of the need to write programs specifically targeted at the new environment.
INT 21h/AH=87h can be used to distinguish between the multitasking MS-DOS 4.x and the later MS-DOS/PC DOS 4.x issues.
Microsoft president Jon Shirley described it as a "specialized version" and went as far as saying "maybe we shouldn't have called it DOS 4.0", although it's not clear whether this was always the intention, or if a more enthusiastic response from OEMs would have resulted in it being the true successor to DOS 3.x. The marketing positioned it as an additional option between DOS 3.x for workstations, and Xenix for higher-end servers and multiuser systems.
BACKUP
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", w ...
DEBUG
In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems.
Debugging tactics can involve int ...
EXE2BIN
The command-line tool exe2bin is a post-compilation utility program available on MS-DOS and other operating systems.
Overview
Early compilers and linkers for the MS-DOS platform could not produce a COM file executable directly. Instead, the co ...
GRAFTABL
This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list.
In DOS, many standard system commands were ...
*
GRAPHICS
Graphics () are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone, to inform, illustrate, or entertain. In contemporary usage, it includes a pictorial representation of data, as in design and manufacture ...
*
GWBASIC
GW-BASIC is a dialect of the BASIC programming language developed by Microsoft from IBM BASICA. Functionally identical to BASICA, its BASIC interpreter is a fully self-contained executable and does not need the Cassette BASIC ROM found in the o ...
PRINT
Printing is the process for reproducing text and images using a master form or template
Print or printing may also refer to:
Publishing
* Canvas print, the result of an image printed onto canvas which is often stretched, or gallery-wrapped, o ...
RESTORE Restore may refer to:
* ReStore - Retail building supply stores run by local Habitat for Humanity affiliates
*"Restore", a single by Chris August
Christopher August Megert (born March 20, 1982) is an American Contemporary Christian musician who ...
Concurrent DOS
Multiuser DOS is a Real-time operating system, real-time multi-user multi-tasking operating system for IBM Personal Computer, IBM PC-compatible microcomputers.
An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 ...
Concurrent DOS 386
Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers.
An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...
- Concurrent CP/M-based multiuser multitasking OS with DOS emulator since 1983
* DOS Plus - Concurrent PC DOS-based multitasking OS with DOS emulator since 1985
* Novell DOS, OpenDOS,
DR-DOS
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
- successors of DOS Plus with preemptive multitasking in VDMs since 1993
* FlexOS - successor of Concurrent DOS 286 since 1986
*
4680 OS
FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business U ...
,
4690 OS
4690 Operating System (sometimes shortened to 4690 OS or 4690) is a specially designed point of sale (POS) operating system, originally sold by IBM. In 2012, IBM sold its retail business, including this product, to Toshiba, which assumed support. ...
- successors of FlexOS 286 and FlexOS 386 since 1986
* Multiuser DOS - successor of Concurrent DOS 386 since 1991
* REAL/32 - successor of Multiuser DOS since 1995
* PC-MOS/386 - multiuser multitasking DOS clone since 1987
* VM/386 - multiuser multitasking DOS environment since 1987
* TopView - DOS-based multitasking environment since 1985
* DESQview,
DESQview/X
DESQview (DV) is 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 allows users to run multiple programs concurrentl ...