Learning MS-DOS Basics - A Tutorial

MS-DOS was a renamed form of 86-DOS[12] – owned by Seattle Computer Products, written by Tim Paterson. Development of 86-DOS took only six weeks, as it was basically a clone of Digital Research s CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M; an improved disk sector buffering logic and the introduction of FAT12 instead of the CP/M filesystem. This first version was shipped in August 1980.[5] Microsoft, which needed an operating system for the IBM Personal Computer[7][8] hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for $75,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS. They also licensed MS-DOS 1.10/1.14 to IBM, who, in August 1981, offered it as PC DOS 1.0 as one of three operating systems[13] for the IBM 5150, or the IBM PC.[5]

Within a year Microsoft licensed MS-DOS to over 70 other companies.[14] It was designed to be an OS 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 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 some standard version for the IBM PC—often the same-numbered version, but not always, since some OEMs used their own proprietary version numbering schemes (e.g. labeling later releases of MS-DOS 1.x as 2.0 or vice versa)—with a few notable exceptions.

Microsoft omitted multi-user support from MS-DOS because Microsoft s Unix-based operating system, Xenix, was fully multi-user.[15] The company planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the Motorola 68000, Zilog Z8000, and the LSI-11; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future".[16][17] Microsoft advertised MS-DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", and promising easy porting between them.[18] After the breakup of the Bell System, however, AT&T Computer Systems started selling UNIX System V. Believing that it could not compete with AT&T in the Unix market, Microsoft abandoned Xenix, and in 1987 transferred ownership of Xenix to the Santa Cruz Operation (SCO).

On March 25, 2014, Microsoft made the code to SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11 available to the public under the Microsoft Research License Agreement, which makes the code source-available, but not open source as defined by Open Source Initiative or Free Software Foundation standards.[2][3][4][19]

As an April Fools joke in 2015, Microsoft Mobile launched a Windows Phone application called MS-DOS Mobile which was presented as a new mobile operating system and worked similar to MS-DOS.[20]


Versions
Main articles: Comparison of DOS operating systems and Timeline of DOS operating systems
Microsoft licensed or released versions of MS-DOS under different names like Lifeboat Associates "Software Bus 86"[21] aka SB-DOS,[10] COMPAQ-DOS,[21] NCR-DOS or Z-DOS[10] before it eventually enforced the MS-DOS name for all versions but the IBM one, which was originally called "IBM Personal Computer DOS", later shortened to IBM PC DOS. (Competitors released compatible 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:[22][23]

MS-DOS 1.x
Version 1.10 (OEM) – possible basis for IBM s Personal Computer DOS 1.0
Version 1.11 (OEM) – possible basis for IBM s Personal Computer DOS 1.0
Version 1.14 (OEM) – possible basis for IBM s Personal Computer DOS 1.0
Version 1.24 (OEM) – basis for IBM s Personal Computer DOS 1.1
Version 1.25 (OEM) – basis for non-IBM OEM versions of MS-DOS, including SCP MS-DOS 1.25
Compaq-DOS 1.12, a Compaq OEM version of MS-DOS (1.25 or higher)
Zenith Z-DOS 1.19, a Zenith OEM version of MS-DOS (1.25 or higher)[24]
MS-DOS 2.x – Support for IBM’s 10 MB hard disk drives, support up to 15 MB hard disk drives max[25], FAT12, user installable device drivers and tree-structure filing system
Version 2.0 (OEM), First version to support 5.25-inch, 360 kB floppy drives and diskettes.[26]
Version 2.1 (OEM)
Version 2.11 (OEM)
Altos MS-DOS 2.11, an Altos OEM version of MS-DOS 2.11 for the ACT-86C
TeleVideo PC DOS 2.11, an TeleVideo OEM version of MS-DOS 2.11
MS-DOS 3.x
Version 3.0 (OEM) – First version to support 5.25-inch, 1.2 MB floppy drives and diskettes, FAT16.
Version 3.1 (OEM) – Support for Microsoft Networks
Version 3.2 (OEM) – First version to support 3.5-inch, 720 kB floppy drives and diskettes.[26]
Version 3.21 (OEM)
Version 3.22 (OEM) – (HP 95LX)
Version 3.25 (OEM)
Version 3.3 (OEM) – First version to support 3.5-inch, 1.44 MB floppy drives and diskettes.
Version 3.3a (OEM)
Version 3.31 (OEM)[nb 1] – supports FAT16B and larger drives.[nb 2]
MS-DOS 4.0 (multitasking) and MS-DOS 4.1 – A separate branch of development with additional multitasking features, released between 3.2 and 3.3, and later abandoned. It is unrelated to any later versions, including versions 4.00 and 4.01 listed below
MS-DOS 4.x (IBM-developed) – includes a graphical/mouse interface. It had many bugs and compatibility issues.[27]
Version 4.00 (OEM) – First version to support a single hard disk partition that is greater than 32 MiB and up to a maximum size of 2 GiB.[28]
Version 4.01 (OEM) – Microsoft rewritten Version 4.00 released under MS-DOS label but not IBM PC DOS. First version to introduce volume serial number when formatting hard disks and floppy disks (Disk duplication also[nb 3] and when using SYS to make a floppy disk or a partition of a hard drive bootable).[29]
Version 4.01a (OEM)
MS-DOS 5.x
Version 5.0 (Retail) – includes a full-screen editor. A number of bugs required reissue. First version to support 3.5-inch, 2.88 MB floppy drives and diskettes. Hard disk partitions greater than 32 MiB and up to a maximum size of 2 GiB was now provided by the MS-DOS kernel.[28] First version to load portions of the operating system into the high memory area.
AST Premium Exec DOS 5.0 (OEM) – a version for the AST Premium Exec series of notebooks with various extensions, including improved load-high and extended codepage support[30][31]
Version 5.0a (Retail) – With this release, IBM and Microsoft versions diverge.
Version 5.50 (Windows NTVDM) – All Windows NT 32-bit versions ship with files from DOS 5.0

Microsoft MS-DOS 6.22
MS-DOS 6.x
Version 6.0 (Retail) – Online help through QBASIC. Disk compression, upper memory optimization and antivirus included.
Version 6.2 – Scandisk as replacement for CHKDSK. Fix serious bugs in DBLSPACE.
Version 6.21 (Retail) – Stacker-infringing DBLSPACE removed.
Version 6.22 (Retail) – New DRVSPACE compression.
MS-DOS 7.x
Version 7.0 (Windows 95, Windows 95A) – Support for VFAT long file names and 32-bits signed integer errorlevel. New editor. JO.SYS is an alternative filename of the IO.SYS kernel file and used as such for "special purposes". JO.SYS allows booting from either CD-ROM drive or hard disk. Last version to recognize only the first 8.4 GB of a hard disk. The "VER" internal command prompt reports the Windows version 4.00.950.
Version 7.1 (Windows 95B – Windows 98 – Windows 98SE) – Support for FAT32 file system. Last general purpose DOS to load Windows. The "VER" internal command prompt reports the Windows version 4.00.1111, 4.10.1998 or 4.10.2222.
MS-DOS 8.0
Version 8.0 (Windows ME) – Integrated drivers for faster Windows loading. Four different kernels (IO.SYS) observed.[nb 4] The "VER" internal command prompt reports the Windows version 4.90.3000.
Version 8.0 (Windows XP) – DOS boot disks created by XP and later contain files from Windows ME. The "VER" internal command prompt reports the Windows version 5.1.
MS-DOS Mobile 1.0 (Windows Phone) – This version was an April Fools Day joke in 2015 by Microsoft. It is available on the Microsoft Store.
Microsoft DOS was released through the OEM channel, until Digital Research 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 IBM DOS 5.00.1, 5.02, 6.00 and PC DOS 6.1, 6.3, 7, 2000 and 7.1.

Localized versions of MS-DOS existed for different markets.[32] While Western issues of MS-DOS evolved around the same set of tools and drivers just with localized message languages and differing sets of supported codepages and keyboard layouts, some language versions were considerably different from Western issues and were adapted to run on localized PC hardware with additional BIOS services not available in Western PCs, support multiple hardware codepages for displays and printers, support DBCS, alternative input methods and graphics output. Affected issues include Japanese (DOS/V), Korean, Arabic (ADOS 3.3/5.0), Hebrew (HDOS 3.3/5.0), Russian (RDOS 4.01/5.0) as well as some other Eastern European versions of DOS.