Writen by : Maya Zurida, M2 TE-TMJK, PNL.
MS-DOS (/ˌɛmɛsˈdɒs/ em-es-doss; short
for Microsoft Disk Operating System) is an operating
system for x86-based personal computers. It was the
most commonly used member of the DOS family
of operating systems, and was the main operating system for IBM
PC compatible personal
computers during the 1980s to the mid-1990s, until it was gradually superseded
by operating systems offering a graphical user interface (GUI),
in particular by various generations of the Microsoft
Windowsoperating system.
MS-DOS
grew out of a request placed by IBM in 1981 for an operating system to use in
its IBM
PCrange of personal computers. Microsoft quickly
bought the rights to QDOS (Quick
and Dirty Operating System), also known as 86-DOS, fromSeattle Computer Products, and
began work on modifying it to meet IBM's specification, who licensed and
released it as PC DOS 1.0
to be used with their PCs in August 1981. Although MS-DOS and PC DOS were
initially developed in parallel by Microsoft and IBM, years later 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 languagescompany
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. It is a flexible
operating system, and consumes only 8 MB of installation space.
History
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. 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. Microsoft,
which needed an operating system for the then-new Intel 8086 but
had none available, 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 the default operating system for the IBM PC.
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 (EMSand 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, 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 MB of total memory address space.
Versions
Microsoft licensed or released
versions of MS-DOS under different names like Lifeboat Associates "Software Bus 86" aka SB-DOS, COMPAQ-DOS, NCR-DOS or Z-DOS 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:
·
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
·
Compaq-DOS
1.12, a Compaq OEM version of MS-DOS (1.25 or higher)
·
MS-DOS 2.x –
Support for 10 MB hard disk drives and tree-structure filing system
·
Version 2.0
(OEM)
·
Version 2.1
(OEM)
·
Version 2.11
(OEM)
·
MS-DOS 3.x
·
Version 3.0 (OEM)
– Support for FAT16. First version to support 5.25 inch, 1.2 MB floppy
drives and diskettes.
·
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.
·
Version 3.21
(OEM)
·
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)
·
MS-DOS 4.x –
includes a graphical/mouse interface. It had many bugs and compatibility
issues.
·
Version 4.00
(OEM)
·
Version 4.01
(OEM) – IBM patched Version 4.00 before Microsoft released it. First version to
introduce volume serial number when formatting hard disks and floppy disks
(Disk duplication also).
·
Version 4.01a
(OEM)
·
MS-DOS 5.x
·
Version 5.0
(Retail) – includes a full-screen editor. A number of bugs required re issue.
First version to support 3.5 inch, 2.88 MB floppy drives and diskettes. First
version to support partition of hard drives up to 2 GiB.
·
Version 5.0a
(Retail) – With this release, IBM and Microsoft versions diverge.
·
Version 5.0.500
(WinNT) – All Windows NT 32-bit versions ship with files from DOS 5.0
·
MS-DOS 6.x
·
Version 6.0
(Retail) – Online help through QBASIC. Disk compression and antivirus included.
·
Version 6.1
(none) – IBM and Microsoft alternate DOS 6 versions. IBM released 6.3 also.
·
Version 6.2 (Retail)
– 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
(Win95, 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 CD-ROM to hard disk.
·
Version 7.1
(Win95B – Win98SE) – Support for FAT32 file system. Last general purpose DOS to load
Windows.
·
MS-DOS 8.0
·
Version 8.0
(WinME) – Integrated drivers for faster Windows loading. Four different kernels
(IO.SYS) observed.
·
Version 8.0
(WinXP) – DOS boot disks created by XP and later contain files from WinME. The
internal command prompt still reports version 5.0
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.
How to Create an MS-DOS Boot Disk
For many years PC users felt as though the days of
DOS were behind them.In recent years, particularly after the release of Windows
Vista, computer enthusiasts have been making multiple boot machines to run
older software. In same cases it is much easier to boot your computer using a
boot disk than going through the hassle of the boot menu.
Instructions
1
Go to a DOS prompt. You
can be at any prompt, although if you have a pre-existing DOS installation
going to your DOS directory (usually c:\DOS) is often the best choice.
2
Insert a blank disk into
your floppy drive.
3
Type "format a:
/s" at the prompt. This will format the disk (even if it is already
formatted for your computer), erase everything on it, and copy your computers
system files to it.
4
Decide if you need any
other utility or driver files. The most common files that are user added to a
boot disk are utilities such as chkdsk or dosshell, or drivers for CD Drives or
a mouse. The utilities are in your DOS directory but the drivers can be in
several places depending on their manufacturer. Check you documentation for
more information.
5
Add an autoexec.bat and
a config.sys file. These files will automate the booting process by loading
drivers and software. By doing this you will be able to make separate disks for
individual programs.
MS-DOS Characteristics
Command
Line Interface
MS-DOS uses a command line interface, forcing the user to input
commands at a prompt. The command set for DOS is limited. It consists mainly of
navigation and file manipulation commands. Most complex operations are handled
by the programs themselves. Since users have to enter commands in sequence,
they could create batch files, which are text files listing a series of
commands that the OS would execute in order. One common example of this is AUTOEXEC.BAT,
a batch file that the OS runs on first boot and contains commands to set up the
computing environment.
Single
Tasks
Because Microsoft intended MS-DOS to run on early PCs without much
in the way of RAM, MS-DOS features no ability for programs to multitask. When
the user runs a program, that program consumes system resources until it stops,
and then another program may access memory. Certain types of programs called
TSRs, for Terminate and Stay Resident, can park themselves in memory, but these
programs are vulnerable to memory overlap and frequently crashed. The first
versions of Windows introduced true multitasking to PCs.
Filenames
One distinctive characteristic of MS-DOS is its “8+3” file naming
system. File names are limited to eight characters, with a three-character
suffix denoting the type of file. For instance, TXT and DOC denote text files,
while COM and EXE indicate executables and SYS is reserved for system files.
Windows has since done away with the eight-character limit, although file
suffixes still indicate to the OS how to handle each type of file, and many of
the original suffixes from the early days of MS-DOS still exist.
Drive
Letters
Another prominent characteristic of MS-DOS is its use of letters
to refer to drives. Typically, A and B designate floppy drives, while C and
anything later in the alphabet refers to hard drives or optical drives. Users
have the ability to map any drive letter they wish, although typically they
would assign them in alphabetical order. Today, Windows still uses drive
letters, and still reserves A and B by default, despite the fact that modern
PCs typically do not contain floppy drives.
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