MS-DOS or Microsoft Disk Operating System is an operating system for x86-based personal computers, which was purchased by Microsoft. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for personal computers during the 1980s up to mid 1990s. It was preceded by M-DOS (also called MIDAS), designed and copyrighted by Microsoft in 1979. MSDOS was written for the Intel 8086 family of microprocessors, particularly the IBM PC and compatibles. It was gradually replaced on consumer desktop computers by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system. MS-DOS developed out of QDOS (Quick and Dirty Operating System), also known as 86-DOS. MS-DOS development originally started in 1981, and was first released in 1982 as MS-DOS 1.0. Several versions were released under different names for different hardware. MS-DOS had eight major versions released before Microsoft stopped development in 2000. 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.
As the name suggests, the operating System is used for operating the system or the computer. It is a set of computer programs and also known as DOS (Disk Operating System). The main functions of DOS are to manage disk files, allocate system resources according to the requirement. DOS provides features essential to control hardware devices such as Keyboard, Screen, Disk Devices, Printers, Modems and programs.
Basically, DOS is the medium through which the user and external devices attached to the system communicate with the system. DOS translates the command issued by the user in the format that is understandable by the computer and instructs computer to work accordingly. It also translates the result and any error message in the format for the user to understand.
Versions
Microsoft licensed or released versions of MS-DOS under different names like SB-DOS or Z-DOS. Competitors released DOS systems such as DR-DOS and PTS-DOS that could also run DOS applications. The following versions of MS-DOS were released to the public:
- MS-DOS 1.x
- Version 1.0 (Retail)
- Version 1.1 (Retail)
- Version 1.12 (Retail)
- Version 1.25 (Retail)
- MS-DOS 2.x - Support for 10 MB Hard Disk Drives and tree-structure filing system
- Version 2.0 (Retail)
- Version 2.1 (Retail)
- Version 2.11 (Retail)
- Version 2.2 (Retail)
- Version 2.21 (Retail)
- MS-DOS 3.x
- Version 3.0 (Retail) - Support for larger Hard Disk Drives
- Version 3.1 (Retail) - Support for Microsoft Networks
- Version 3.2 (Retail)
- Version 3.21 (Retail)
- Version 3.25 (Retail)
- Version 3.3 (Retail)
- Version 3.3a (Retail)
- Version 3.3r (Retail)
- Version 3.31 (Retail)
- Version 3.35 (Retail)
- MS-DOS 4.x - includes a graphical/mouse interface.
- Version 4.0 (Retail)
- Version 4.01 (Retail)
- MS-DOS 5.x
- Version 5.0 (Beta 1)
- Version 5.0 (Retail) - includes a full-screen editor
- Version 5.0a (Retail)
- MS-DOS 6.x
- Version 6.0 (Retail)
- Version 6.1 (Retail)
- Version 6.2b (RTM)
- Version 6.2 (Retail)
- Version 6.21 (Retail)
- Version 6.22 (Retail)
- MS-DOS 7.x
- Version 7.0 (Beta)
Version 7.1 (Retail)
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.
Several limitations plague the DOS architecture. The original 8088 microprocessor could only address 1 megabyte of physical RAM. With additional hardware devices being mapped into this range, the highest amount of available memory was 640 kilobytes, known as conventional memory. Due to DOS' structure, this was assumed to be the maximum, and DOS could not address more than this. An early workaround was expanded memory; later, extended memory was developed with the 80286. While these provided usable memory to applications, they still had to start in conventional memory, thereby using part of the existing 640 KB. With the 80386 microprocessor's redesigned protected mode, DOS extenders and the DOS Protected Mode Interface were able to provide additional memory to applications, as well as multitasking.
DOS also has an upper limit to the size of hard disk partitions. This has two causes. First, many DOS-type systems never had support for any file system newer than FAT16, which, by design, does not allow partitions larger than 2.1 gigabytes. Additionally, DOS accesses the hard disk by calling Interrupt 13, which utilizes the cylinder-head-sector system of mapping the disk. Under this system, only 8 gigabytes are visible to the operating system. Newer operating systems accomplished disk access via software means, e.g. 32-bit disk access.
Using FAT16 (and FAT12 for floppy disks) required use of the 8.3 filename. Filenames in DOS cannot be longer than eight characters, and the filename extension cannot be longer than three. Win95's patented VFAT hack worked around this in a unique way.
Windows XP contains a copy of the core MS-DOS 8 files from Windows Me, accessible only by formatting a floppy as an "MS-DOS startup disk". These core files are a stripped down bootstrap only, which does not include CD-ROM support. 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 (C) Copyright 1981-1999 Microsoft Corp" inside
COMMAND.COM.Today, 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.
Microsoft has introduced a new command-line called PowerShell. Powershell offers more functionality than MS-DOS.
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