Name | MS-DOS |
---|---|
Logo | |
Screenshot | |
Developer | Microsoft Corporation |
Source model | Closed source |
Kernel type | Monolithic kernel |
Supported platforms | x86 |
Ui | Command-line interface, Text user interface |
Family | DOS |
Released | 1981 |
Latest release version | 8.0 |
Latest release date | |
Programmed in | Assembly language |
Prog language | C, Pascal, QBasic, Batch, etc. |
Language | Multilanguage |
Working state | Discontinued/Historic |
License | Proprietary |
Support status | Unsupported, starting from 31 December 2001 }} |
MS-DOS grew from a 1981 request by IBM for an operating system for its IBM PC range of personal computers. Microsoft quickly bought the rights to QDOS (Quick and Dirty Operating System), also known as 86-DOS, from Seattle Computer Products, and began work on modifying it to meet IBM's specification. The first edition, MS-DOS 1.0, was launched in 1982. The version shipped with IBM's PCs was called PC DOS. Although MS-DOS and PC-DOS were initially developed in parallel by Microsoft and IBM, the two products eventually went their separate ways.
During its life, several competing products were released for the x86 platform, and MS-DOS itself would go through eight versions, until development ceased in 2000. Ultimately it was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.
MS-DOS was a renamed form of 86-DOS – informally known as the Quick-and-Dirty Operating System or Q-DOS – owned by Seattle Computer Products, written by Tim Paterson. Microsoft needed an operating system for the then-new Intel 8086 but it had none available, so it bought 86-DOS for $75,000 and licensed it as its own then released a version of it as MS-DOS 1.0. Development started in 1981, and MS-DOS 1.0 was released with the IBM PC in 1982 (86-DOS, in turn, was written as a clone of CP/M, with the exception of how drives internal to the system were referenced. In CP/M the hard drive was referenced with A:, where as 86-DOS referred to the hard drive with C:.) Tim Paterson is considered the original author of DOS and he is called "The Father of DOS".
Originally MS-DOS was designed to be an operating system that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers, minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could only run software written exclusively for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture.
This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, and indeed the same design philosophy is embodied in Windows NT (see Hardware Abstraction Layer). However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance, especially for games, which often pushed the limits of their contemporary hardware. Very soon an IBM-compatible architecture became the goal, and before long all 8086-family computers closely emulated IBM's hardware, and only a single version of MS-DOS for a fixed hardware platform was needed for the market. This version is the version of MS-DOS that is discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, and in any case were very similar in function and capability to the same-numbered standard version for the IBM PC, with a few notable exceptions.
While MS-DOS appeared on PC clones, true IBM computers used PC DOS, a rebranded form of MS-DOS. Ironically, the dependence on IBM-compatible hardware caused major problems for the computer industry when the original design had to be changed. For example, the original design could support no more than 640 kilobytes of memory (the 640 kB barrier), because IBM's hardware design reserved the address space above this limit for peripheral devices and ROM. Manufacturers had to develop complicated schemes (EMS and XMS, and other minor proprietary ones) to access additional memory. This limitation would not have been a problem if the original idea of interfacing with hardware through MS-DOS had endured. (However, MS-DOS was also a real-mode operating system, and the Intel x86 architecture only supports up to 1 MB of memory address space in Real Mode, even on Pentium 4 and later x86 CPUs, so for simple access to megabytes of memory, MS-DOS would have had to be rewritten to run in 80286 or 80386 Protected Mode.) Also, Microsoft originally described MS-DOS as "an operating system for Intel 8086-based microcomputers", and the 8086 CPU (and its cousin the 8088) itself has only 1 MiB of total memory address space.
Microsoft DOS was released through the OEM channel, until DRI released DR-DOS 5.0 as a retail upgrade. With PC-DOS 5.00.1, the IBM-Microsoft agreement started to end, and IBM entered the retail DOS market with IBMDOS 5.00.1, 5.02, 6.00 and PC-DOS 6.10, 6.30, 7.00 and 2000.
A number of beta versions have surfaced on the Internet, such as 5.0 (a ten-diskette version in the same vein as 4.0), 7.00 beta 1 (based on 6.00), 7.00 beta 2 (based on 6.22). An OEM source package for 6.00, and a late release of 6.2(b) have also been seen. These are not retail versions.
On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether Q-DOS was more or less plagiarised from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft's licensing requirements, but at a higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; much applications software was sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS supported the simple .COM and the more advanced relocatable .EXE executable file formats; CP/M-86 a relocatable format using the file extension .CMD.
Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in. Users who began using MS-DOS with their machines were compelled to continue using the version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system.
In the business world the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix.
In the emerging world of home users, a variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II, early Apple Macintosh, the Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with the PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had a large share of the business computer market.
Microsoft and IBM together began what was intended as the follow-on to MS/PC DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead" and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking — an IBM speciality derived from deep experience with mainframe operating systems — and offered a number of advanced features that had been designed together with similar look and feel; it was seen as the legitimate heir to the "kludgy" DOS platform.
MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft's other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, Stacker disk compression, and others.
During the period when Digital Research was competing in the operating system market some computers, like Amstrad PC-1512, were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus, which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format.
While OS/2 was under protracted development, Digital Research released the MS-DOS compatible DR-DOS 5, which included features only available as third-party add-ons for MS-DOS (and still maintained considerable internal CP/M-86 compatibility). Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most DR-DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR-DOS 6, which sold well until the "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR-DOS.
Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty, and doubt) regarding DR-DOS. For example, in October 1990, shortly after the release of DR-DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in ''InfoWorld'' and ''PC Week''. Brad Silverberg, Vice President of Systems Software at Microsoft and General Manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to ''PC Week'' (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copied features from DR-DOS:
"The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR-DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of the same requests from customers that we have." – (Schulman et al. 1994).
The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft's further contributions to OS/2 also went in to creating a third GUI replacement for DOS, Windows NT.
IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows.
MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk-compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code.
Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR-DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages. It was believed that the settlement ran in the order of $150m, but was revealed in November 2009 with the release of the Settlement Agreement to be $280m.
Microsoft's QuickPascal released in early 1989 was the first MS product that checked for MS-DOS by modifying the program's Program Segment Prefix using undocumented DOS functions, and then checked whether or not the associated value changed in a fixed position within the DOS data segment (also undocumented). This check also made it into later MS products, including Microsoft QuickC v2.5, Programmer's Workbench and Microsoft C v6.0. The (once infamous) AARD code, a block of code in the Windows 3.1 beta installer. It was XOR encrypted, self-modifying, and deliberately obfuscated, using various undocumented DOS structures and functions to determine whether or not Windows really was running on MS-DOS.
Today, MS-DOS is rarely used for desktop computing. Since the release of Windows 95, it was integrated as a full product used for bootstrapping and troubleshooting, and no longer released as a standalone product.
Windows XP contains a copy of the Windows Me boot disk, stripped down to bootstrap only. This is accessible only by formatting a floppy as an "MS-DOS startup disk". Files like the driver for the CD-ROM support were deleted from the Windows ME bootdisk and the startup files (AUTOEXEC.BAT and CONFIG.SYS) no longer had a content. This modified disk was the base for creating the MS-DOS image for Windows XP. Some of the deleted files can be recovered with an undelete tool. With Windows Vista the files on the startup disk are dated 18 April 2005 but are otherwise unchanged, including the string "MS-DOS Version 8 © Copyright 1981-1999 Microsoft Corp" inside COMMAND.COM
.
However the only versions of DOS currently recognized as stand-alone OSs, and supported as such by the Microsoft Corporation are DOS 6.0 and 6.22, both of which remain available for download via their MSDN, volume license, and OEM license partner websites, for customers with valid login credentials.
MS-DOS is still used in embedded x86 systems due to its simple architecture, and minimal memory and processor requirements. The command line interpreter of NT-based versions of Windows, cmd.exe, maintains most of the same commands and some compatibility with DOS batch files.
Consumer Windows (up to 3.11, Win9x, WinME) ran as a Graphical User Interface (GUI) running on top of MS-DOS. With Windows 95, 98, and ME the MS-DOS part was integrated to give the illusion of a new operating system. The command line accessed the DOS command line (usually command.com), through a Windows module (winoldap.mod).
A new line of Windows, (Windows NT), boot through a kernel whose sole purpose is to load Windows: there is no character-mode boot similar to Consumer Windows, OS/2 or UNIX). The console runs as a Win32 session, with the default processor cmd.exe
being a feature-reduced version of OS/2's version. The command session permits running of various supported command line utilities from Win32, MS-DOS, OS/2 1.x and POSIX.
The 32-bit Windows can run MS-DOS programs through the use of the NTVDM (NT Virtual DOS Machine). This launches a stubbed version of MS-DOS 5.0. Launching any DOS application such as the DOS command processor command.com
creates a 16-bit sub-system providing most of the higher level DOS APIs for DOS programs to run and even communicate with each other.
The 32-bit CLI is usually referred to as the MS-DOS prompt. Although the binary interface is no longer that found in PC-DOS etc., it is an 'interface', and not an API. The commands typed here, the batches etc., all resemble those of MS/PC-DOS in much the same way that the Linux/UNIX commands resemble each other without underlying binary compatibility.
All versions of Windows for x86-64 and Itanium architectures no longer include the NTVDM and can therefore no longer natively run MS-DOS or 16-bit Windows applications. There are alternatives in the form of Virtual machine emulators such as Microsoft's own Virtual PC, as well as VMware, DOSBox, and others.
Later, in 1985, Microsoft Windows was released as Microsoft's first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS and its clones. At first Windows met with little success, but this was also true for most other companies' efforts as well, for example GEM. After version 3.0 (1990), Windows gained market acceptance.
Later versions (Windows 95, Windows 98 and Windows Me) used the DOS boot process to launch itself into protected mode. Basic features related to the file system, such as long file names, were only available to DOS when running as a subsystem of Windows. Windows NT ran independently of DOS but included a DOS subsystem so applications could run in a virtual machine under the new OS. With the latest Windows releases, even dual-booting MS-DOS is problematic as DOS may not be able to read the basic file system.
These products are collectively referred to as DOS. However, MS-DOS can be a generic reference to DOS on IBM-PC compatible computers.
Category:Article Feedback Pilot Category:1981 software Category:Discontinued Microsoft operating systems Category:DOS on IBM PC compatibles Category:Floppy disk-based operating systems
af:MS-DOS ar:إم إس-دوس az:MS-DOS bn:এমএস-ডস zh-min-nan:MS-DOS be:MS-DOS bg:MS-DOS ca:MS-DOS cs:MS-DOS da:MS-DOS de:MS-DOS et:MS-DOS el:MS-DOS es:MS-DOS eo:MS-DOS eu:MS-DOS fa:اماس-داس fo:MS-DOS fr:MS-DOS fy:MS-DOS ga:MS-DOS gl:MS-DOS ko:MS-DOS hr:MS-DOS id:MS-DOS it:MS-DOS he:MS-DOS jv:MS-DOS kk:MS-DOS ku:MS-DOS lv:MS-DOS lt:MS-DOS hu:MS-DOS ml:എം.എസ്-ഡോസ് mr:एमएस-डॉस ms:MS-DOS nl:MS-DOS ja:MS-DOS no:MS-DOS nn:MS-DOS uz:MS-DOS nds:MS-DOS pl:MS-DOS kaa:MS-DOS ro:MS-DOS ru:MS-DOS simple:MS-DOS sk:MS-DOS sr:MS-DOS sh:MS-DOS fi:MS-DOS sv:MS-DOS tl:MS-DOS tr:MS-DOS uk:MS-DOS vi:MS-DOS fiu-vro:MS-DOS yi:MS-DOS zh:MS-DOSThis text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
A repair technician might work in a corporate information technology department, a central service center, or a retail computer sales environment. A public sector technician might work in the military, national security or law enforcement communities, health or public safety field, or an educational institution. Despite the vast variety of work environments, all computer technicians perform similar physical and investigative processes, including technical support. Experienced technicians might specialize in fields such as data recovery, system administration, or information systems. Some technicians are self-employed or own a firm that provides services in a regional area. Some are subcontracted as freelancers or consultants. This type of technician ranges from hobbyists and enthusiasts that volunteer or make a little side money, to those who work professionally in the field.
The repair of problems can range from a minor setting that is incorrect, to spyware, viruses, and as far as replacing hardware or an entire operating system. Some technicians provide on-site services usually at an hourly rate. Others can provide services off-site, where the client can drop off at the repair shop. Some have pickup and drop off services for convenience. Some may also take back old equipment for recycling (In the EU, this is required under WEEE rules).
Category:Computer occupations Computer repair technician Category:Technicians
he:טכנאי מחשביםThis text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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