DOS (/dɒs/, /dɔːs/) is a family of disk operating systems.
DOS primarily consists of
MS-DOS and a rebranded version under the
IBM PC DOS, both of which were introduced in 1981. Other later
compatible systems from other manufacturers include
PTS-DOS (1993), and
IBM PC compatible
IBM PC compatible market between 1981 and 1995.
Dozens of other operating systems also use the acronym "DOS",
including the mainframe DOS/360 from 1966. Others are Apple DOS, Apple
ProDOS, Atari DOS, Commodore DOS, TRSDOS, and AmigaDOS.
1.3 Continued use
1.3.1 Embedded systems
2.1 Boot sequence
2.2.1 Drive naming scheme
2.2.2 Reserved device names
2.3 Memory management
OS/2 and Windows
3 User interface
3.1 Terminate and Stay Resident
5 See also
7 Further reading
8 External links
Comparison of DOS operating systems and Timeline
DOS operating systems
IBM PC DOS
IBM PC DOS (and the separately sold MS-DOS) and its predecessor,
86-DOS, resembled Digital Research's CP/M—the dominant disk
operating system for 8-bit
Intel 8080 and Zilog Z80
microcomputers—but instead ran on
When IBM introduced the IBM PC, built with the
microprocessor, they needed an operating system. Seeking an
8088-compatible build of CP/M, IBM initially approached
Bill Gates (possibly believing that
CP/M due to the
Microsoft Z-80 SoftCard, which allowed
CP/M to run on an Apple II).
IBM was sent to Digital Research, and a meeting was set up. However,
the initial negotiations for the use of
CP/M broke down; Digital
Research wished to sell
CP/M on a royalty basis, while IBM sought a
single license, and to change the name to "PC DOS". Digital Research
Gary Kildall refused, and IBM withdrew.
IBM again approached Bill Gates. Gates in turn approached Seattle
Computer Products. There, programmer
Tim Paterson had developed a
variant of CP/M-80, intended as an internal product for testing SCP's
CPU card for the S-100 bus. The system was
initially named Q
DOS (Quick and Dirty Operating System), before being
made commercially available as 86-DOS.
Microsoft purchased 86-DOS,
allegedly for $50,000. This became
Microsoft Disk Operating System,
MS-DOS, introduced in 1981.
Within a year
MS-DOS to over 70 other companies,
which supplied the operating system for their own hardware, sometimes
under their own names.
Microsoft later required the use of the MS-DOS
name, with the exception of the IBM variant. IBM continued to develop
their version, PC DOS, for the IBM PC.
Digital Research became
aware that an operating system similar to
CP/M was being sold by IBM
(under the same name that IBM insisted upon for CP/M), and threatened
legal action. IBM responded by offering an agreement: they would give
PC consumers a choice of
PC DOS or CP/M-86, Kildall's 8086 version.
CP/M cost almost $200 more than PC DOS, and sales were
CP/M faded, with
PC DOS becoming the marketed
operating system for PCs and PC compatibles.
Microsoft originally sold
MS-DOS only to original equipment
manufacturers (OEMs). One major reason for this was that not all early
PCs were 100%
IBM PC compatible.
DOS was structured such that there
was a separation between the system specific device driver code
(IO.SYS) and the D
OS kernel (MSDOS.SYS).
Microsoft provided an OEM
Adaptation Kit (OAK) which allowed OEMs to customize the device driver
code to their particular system. By the early 1990s, most PCs adhered
IBM PC standards so
Microsoft began selling
MS-DOS in retail with
In the mid-1980s
Microsoft developed a multitasking version of
DOS. This version of
DOS is generally referred to as "European
MS-DOS 4" because it was developed for ICL and licensed to several
European companies. This version of
DOS supports preemptive
multitasking, shared memory, device helper services and New Executable
("NE") format executables. None of these features were used in later
versions of DOS, but they were used to form the basis of the
kernel. This version of
DOS is distinct from the widely released
DOS 4.0 which was developed by IBM and based upon
Digital Research attempted to regain the market lost from CP/M-86,
initially with Concurrent DOS,
DOS Plus (both compatible
CP/M-86 software), later with Multiuser DOS
(compatible with both
CP/M-86 software) and DR DOS
Digital Research was bought by
Novell, and DR
DOS 7; later, it was part of
Caldera (under the names
DR-DOS 7.02/7.03), Lineo, and
Gordon Letwin wrote in 1995 that "
DOS was, when we first wrote it, a
one-time throw-away product intended to keep IBM happy so that they'd
buy our languages".
Microsoft expected that it would be an interim
solution before Xenix. 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 Z-8000, and
LSI-11; they would be upwardly compatible with Xenix, which
1983 described as "the multi-user
MS-DOS of the future".
IBM, however, did not want to replace DOS. After AT&T began
Microsoft and IBM began developing
OS/2 as an
alternative. The two companies later had a series of disagreements
over two successor operating systems to DOS,
OS/2 and Windows.
They split development of their
DOS systems as a result. The last
retail version of
MS-DOS 6.22, after this
part of Windows 95, 98 and Me. The last retail version of
PC DOS was
PC DOS 2000 (a.k.a.
PC DOS 7 revision 1) though IBM did later develop
PC DOS 7.10 for OEMs and internal use.
FreeDOS project began 26 June 1994, when
Microsoft announced it
would no longer sell or support MS-DOS. Jim Hall then posted a
manifesto proposing the development of an open-source replacement.
Within a few weeks, other programmers including
Pat Villani and Tim
Norman joined the project. A kernel, the
COMMAND.COM command line
interpreter (shell) and core utilities were created by pooling code
they had written or found available. There were several official
pre-release distributions of
FreeDOS before the
distribution was released on 3 September 2006. Made available under
GNU General Public License
GNU General Public License (GPL),
FreeDOS does not require license
fees or royalties.
Main article: History of
Early versions of
Microsoft Windows ran on a separate version of
DOS. By the early 1990s, the Windows graphical shell saw heavy use
DOS systems. In 1995,
Windows 95 was bundled as a standalone
operating system that did not require a separate
DOS license. Windows
95 (and Windows 98 and ME, that followed it) took over as the default
OS kernel, though the
MS-DOS component remained for compatibility.
Windows 95 and 98, but not ME, the
MS-DOS component could be run
without starting Windows. With
DOS no longer required to
use Windows, the majority of PC users stopped using it directly.
DOS systems in 2012 are FreeDOS, DR-DOS, ROM-DOS, PTS-DOS,
DOS and REAL/32. Some computer manufacturers, including
Dell and HP,
sell computers with
FreeDOS as the OEM operating system.
DOS's structure of accessing hardware directly makes it ideal for use
in embedded devices. The final versions of
DR-DOS are still aimed at
ROM-DOS was used as the embedded system on the Canon
PowerShot Pro 70.
On Linux, it is possible to run copies of
DOS and many of its clones
on DOSEMU, a Linux-native virtual machine for running
DOS programs at
near native speed. There are a number of other emulators for running
DOS on various versions of
Microsoft Windows such as
DOSBox is designed for legacy gaming (e.g. King's
Quest, Doom) on modern operating systems.
All MS-DOS-type operating systems run on machines with the
or compatible CPUs, mainly the
IBM PC and compatibles.
Machine-dependent versions of
MS-DOS were produced for many
non-IBM-compatible x86-based machines, with variations from
relabelling of the
Microsoft distribution under the manufacturer's
name, to versions specifically designed to work with
non-IBM-PC-compatible hardware. For as long as application programs
DOS APIs instead of direct hardware access, they could thereby
also run on non-IBM-PC compatible machines. In 1985, Digital Research
also had a version of
Concurrent DOS 68K for use on Motorola 68000
CPUs, and the original
DOS-C derived from DOS/NT, also
for Motorola CPUs, in the early 1990s. While these systems resembled
DOS architecture, applications were not binary compatible due to
the incompatible instruction sets of these non-x86-CPUs. However,
applications written in high-level languages could be ported easily.
DOS is a single-user, single-tasking operating system with basic
kernel functions that are non-reentrant: only one program at a time
can use them and
DOS itself has no functionality to allow more than
one program to execute at a time. The D
OS kernel provides various
functions for programs (an application program interface), like
character I/O, file management, memory management, program loading and
DOS by default provides a primitive ability for shell scripting, via
batch files (with the filename extension .BAT). These are text files
that can be created in any text editor. They are executed in the same
fashion as compiled programs, and run each line of the batch file as a
command. Batch files can also make use of several internal commands,
GOTO and conditional statements.
GOSUB and simple
arithmetic is supported with the DR
COMMAND.COM as well as
some with third-party shells like 4DOS; however, no real form of
programming is usually enabled.
The operating system offers an application programming interface that
allows development of character-based applications, but not for
accessing most of the hardware, such as graphics cards, printers, or
mice. This required programmers to access the hardware directly,
usually resulting in each application having its own set of device
drivers for each hardware peripheral. Hardware manufacturers would
release specifications to ensure device drivers for popular
applications were available.
The bootstrap loader on PC-compatible computers (MBR or boot sector)
is located at track zero, the first sector on a disk. The ROM BIOS
will load this sector into memory at address 0000h:7C00h, and
typically check for a signature "55h AAh" at offset +1FEh. If the
sector is not considered to be valid, the ROM
BIOS will try the next
physical disk in the row, otherwise it will jump to the load address
with certain registers set up.
If the loaded boot sector happens to be a
Master Boot Record
Master Boot Record (MBR), as
found on partitioned media, it will relocate itself to 0000h:0600h in
memory, otherwise this step is skipped. The MBR code will scan the
partition table, which is located within this sector, for an active
partition (modern MBRs check if bit 7 is set at offset +1BEh+10h*n,
whereas old MBRs simply check for a value of 80h), and, if found, load
the first sector of the corresponding partition, which holds the
Volume Boot Record
Volume Boot Record (VBR) of that volume, into memory at 0000h:7C00h in
the similar fashion as it had been loaded by the ROM
BIOS itself. The
MBR will then pass execution to the loaded portion with certain
registers set up.
The sector content loaded at 0000h:7C00h constitutes a VBR now. VBRs
are operating system specific and cannot be exchanged between
DOS versions in general, as the exact behaviour differs
DOS versions. In very old versions of
DOS such as
DOS 1.x, the VBR would load the whole IO.SYS/
IBMBIO.COM file into
memory at 0000h:0600h. For this to work, these sectors had to be
stored in consecutive order on disk by SYS. In later issues, it would
locate and store the contents of the first two entries in the root
directory at 0000h:0500h and if they happen to reflect the correct
boot files as recorded in the VBR, the VBR would load the first 3
consecutive sectors of the IO.SYS/
IBMBIO.COM file into memory at
0070h:0000h. The VBR also has to take care to preserve the contents of
the Disk Parameter Table (DPT). Finally, it passes control to the
loaded portion by jumping to its entry point with certain registers
set up (with considerable differences between different
DOS versions, where the VBR has loaded only the first 3
sectors of the IO.SYS/
IBMBIO.COM file into memory, the loaded portion
contains another boot loader, which will then load the remainder of
itself into memory, using the root directory information stored at
0000h:0500h. For most versions, the file contents still need to be
stored in consecutive order on disk. In older versions of DOS, which
were still loaded as a whole, this step is skipped.
DOS system initialization code will initial its builtin device
drivers and then load the
DOS kernel, located in
MSDOS.SYS on MS-DOS
systems, into memory as well. In Windows 9x, the
initialization code and builtin device drivers and the D
OS kernel are
combined into a single
IO.SYS file while
MSDOS.SYS is used as a text
CONFIG.SYS file is then read to parse configuration parameters.
The SHELL variable specifies the location of the shell which defaults
The shell is loaded and executed.
The startup batch file
AUTOEXEC.BAT is then run by the shell.
DOS system files loaded by the boot sector must be contiguous and
be the first two directory entries. As such, removing and adding
this file is likely to render the media unbootable. It is, however,
possible to replace the shell at will, a method that can be used to
start the execution of dedicated applications faster. This limitation
does not apply to any version of DR DOS, where the system files
can be located anywhere in the root directory and do not need to be
contiguous. Therefore, system files can be simply copied to a disk
provided that the boot sector is DR
DOS compatible already.
DOS and DR
DOS 5.0 and above, the
DOS system files are
IBMBIO.COM instead of
IBMDOS.COM instead of
MSDOS.SYS. Older versions of DR
DOS used DRBIOS.SYS and
MS-DOS 7.0 the binary system files
IO.SYS and MSDOS.SYS
were combined into a single file
MSDOS.SYS became a
configuration file similar to
CONFIG.SYS and AUTOEXEC.BAT. If the
MSDOS.SYS BootGUI directive is set to 0, the boot process will stop
with the command processor (typically COMMAND.COM) loaded, instead of
executing WIN.COM automatically.
DOS uses a filesystem which supports 8.3 filenames: 8 characters for
the filename and 3 characters for the extension. Starting with
hierarchical directories are supported. Each directory name is also
8.3 format but the maximum directory path length is 64 characters due
to the internal current directory structure (CDS) tables that DOS
maintains. Including the drive name, the maximum length of a fully
qualified filename that
DOS supports is 80 characters using the format
drive:pathfilename.ext followed by a null byte.
DOS uses the
File Allocation Table (FAT) filesystem. This was
FAT12 which supported up to 4078 clusters per drive. DOS
3.0 added support for
FAT16 which used
16-bit allocation entries and
supported up to 65518 clusters per drive. Compaq
MS-DOS 3.31 added
FAT16B which removed the 32 MB drive limit and could
support up to 512 MB. Finally
MS-DOS 7.1 (the
DOS component of
Windows 9x) added support for
FAT32 which used 32-bit allocation
entries and could support hard drives up to 137 GB and beyond.
DOS 3.1, file redirector support was added to DOS. This
was initially used to support networking but was later used to support
CD-ROM drives with MSCDEX. IBM PC
DOS 4.0 also had preliminary
installable file system (IFS) support but this was unused and removed
Drive naming scheme
Main article: Drive letter assignment
In DOS, drives are referred to by identifying letters. Standard
practice is to reserve "A" and "B" for floppy drives. On systems with
only one floppy drive
DOS assigns both letters to the drive, prompting
the user to swap disks as programs alternate access between them. This
facilitates copying from floppy to floppy or having a program run from
one floppy while accessing its data on another.
Hard drives were
originally assigned the letters "C" and "D".
DOS could only support
one active partition per drive. As support for more hard drives became
available, this developed into first assigning a drive letter to each
drive's active primary partition, then making a second pass over the
drives to allocate letters to logical drives in the extended
partition, then a third pass to give any other non-active primary
partitions their names (where such additional partitions existed and
contained a DOS-supported file system). Lastly,
DOS allocates letters
for optical disc drives, RAM disks, and other hardware. Letter
assignments usually occur in the order the drivers are loaded, but the
drivers can instruct
DOS to assign a different letter; drivers for
network drives, for example, typically assign letters nearer the end
of the alphabet.
DOS applications use these drive letters directly (unlike the
/dev directory in
Unix-like systems), they can be disrupted by adding
new hardware that needs a drive letter. An example is the addition of
a new hard drive having a primary partition where a pre-existing hard
drive contains logical drives in extended partitions; the new drive
will be assigned a letter that was previously assigned to one of the
extended partition logical drives. Moreover, even adding a new hard
drive having only logical drives in an extended partition would still
disrupt the letters of RAM disks and optical drives. This problem
persisted through Microsoft's DOS-based 9x versions of Windows until
they were replaced by versions based on the NT line, which preserves
the letters of existing drives until the user changes them. Under
DOS, this problem can be worked around by defining a SUBST drive and
DOS program into this logical drive. The assignment of
this drive would then be changed in a batch job whenever the
application starts. Under some versions of Concurrent DOS, as well as
under Multiuser DOS, System Manager and REAL/32, the reserved drive
letter L: will automatically be assigned to the corresponding load
drive whenever an application starts.
Reserved device names
Main article: Device file
There are reserved device names in
DOS that cannot be used as
filenames regardless of extension as they are occupied by built-in
character devices. These restrictions also affect several Windows
versions, in some cases causing crashes and security
The reserved names are: CON (for console), AUX (for auxiliary),
PRN (for printer) and LST (for lister), which were introduced with
86-DOS 1.10 and PC
DOS 1.0 added NUL. Except for LST
they continued to be supported in all versions of MS-DOS,
PC DOS and
DR-DOS ever since. LST was also available in some OEM versions of
MS-DOS 1.25, whereas other OEM versions of
MS-DOS 1.25 already used
LPT1 (first line printer) and COM1 (first serial communication device)
instead, as introduced with PC DOS. In addition to LPT1 and LPT2 as
well as COM1 to COM3, Hewlett-Packard's
MS-DOS 2.11 for the HP
Portable Plus also supported LST as alias for LPT2 and 82164A as alias
for COM2; it also supported PLT for plotters.
Otherwise, COM2, LPT2, LPT3 and the CLOCK$ (still named CLOCK in some
MS-DOS 2.11) clock device were introduced with
DOS 2.0, and COM3 and COM4 were added with
DOS 3.3. Only the
MS-DOS 4 supported KEYBD$ and SCREEN$.
DR DOS 5.0 and
Multiuser DOS support an
$IDLE$ device for dynamic idle
detection to saving power and improve multitasking. LPT4 is an
optional built-in driver for a fourth line printer supported in some
DR-DOS since 7.02. CONFIG$ constitutes the real mode PnP
AUX typically defaults to COM1, and PRN to LPT1 (LST), but these
defaults can be changed in some versions of
DOS to point to other
serial or parallel devices. PLT was reconfigurable as
Filenames ended with a colon (:) such as NUL: conventionally indicate
device names, but the colon is not actually a part of the name of the
built-in device drivers. Colons are not necessary to be typed in some
cases, for example:
ECHO This achieves nothing > NUL
It is still possible to create files or directories using these
reserved device names, such as through direct editing of directory
data structures in disk sectors. Such naming, such as starting a file
name with a space, has sometimes been used by viruses or hacking
programs to obscure files from users who do not know how to access
Parallel port and Serial port
DOS memory management
DOS was originally designed for the
Intel 8086/8088 processor and
therefore could only directly access a maximum of 1 MB of RAM. Due to
PC architecture only a maximum of 640 KB (known as conventional
memory) is available as the upper 384 KB is reserved.
Specifications were developed to allow access to additional memory.
The first was the
Expanded Memory Specification
Expanded Memory Specification (EMS) which originally
allowed memory on an add-on card to be accessed via a 64 KB page frame
in the reserved upper memory area. 80386 and later systems could use a
virtual 8086 mode (V86) mode memory manager like
EMM386 to create
expanded memory from extended memory without the need of an add-on
card. The second specification was the Extended Memory Specification
(XMS) for 80286 and later systems. This provided a way to copy data to
and from extended memory, access to the 65520-byte High Memory Area
(HMA) directly above the first megabyte of memory and the Upper Memory
Block (UMB) area. Generally XMS support was provided by
HIMEM.SYS or a
V86 mode memory manager like
386MAX which also supported EMS.
DOS could directly take advantage of the HMA by
loading its kernel code and disk buffers there via the DOS=HIGH
statement in CONFIG.SYS.
DOS 5+ also allowed the use of available UMBs
via the DOS=UMB statement in CONFIG.SYS.
OS/2 and Windows
See also: Virtual
DOS emulation in
OS/2 and Windows runs in much the same way as
native applications do. They can access all of the drives and
services, and can even use the host's clipboard services. Because the
drivers for file systems and such forth reside in the host system, the
DOS emulation needs only provide a
DOS API translation layer which
DOS calls to
OS/2 or Windows system calls. The translation
layer generally also converts
BIOS calls and virtualizes common I/O
port accesses which many
DOS programs commonly use.
In Windows 3.1 and 9x, the
DOS virtual machine is provided by
WINOLDAP. WinOldAp creates a virtual machine based on the program's
PIF file, and the system state when Windows was loaded. The DOS
graphics mode, both character and graphic, can be captured and run in
DOS applications can use the Windows clipboard by
accessing extra published calls in WinOldAp, and one can paste text
through the WinOldAp graphics.
OS/2 and Windows NT is based upon
DOS 5. Although
there is a default configuration (config.sys and autoexec.bat), one
can use alternate files on a session-by-session basis. It is possible
to load drivers in these files to access the host system, although
these are typically third-party.
OS/2 2.x and later, the
DOS emulation is provided by DOSKRNL.
This is a file that represents the combined
IBMBIO.COM and IBMDOS.COM,
the system calls are passed through to the
OS/2 windowing services.
DOS programs run in their own environment, the bulk of the DOS
utilities are provided by bound
DOS / OS2 applications in the OS2
OS/2 can run Windows 3.1 applications by using a modified
copy of Windows (Win-OS/2). The modifications allow Windows 3.1
programs to run seamlessly on the
OS/2 desktop, or one can start a
OS/2 desktop, similar to starting Windows from DOS.
OS/2 allows for '
DOS from Drive A:', (VMDISK). This is a real DOS,
MS-DOS 6.22 or PC
DOS 5.00. One makes a bootable floppy disk
of the DOS, add a number of drivers from OS/2, and then creates a
special image. The
DOS booted this way has full access to the system,
but provides its own drivers for hardware. One can use such a disk to
access cdrom drives for which there is no
In Windows NT (2000, XP, Vista, 7), the
DOS emulation is provided by
way of a virtual
DOS machine (NTVDM). The
DOS files reside in NTIO.SYS
IO.SYS as usual, but run in the virtual machine provided by
NTVDM. The character input is passed to the console session that
DOS program. This allows one to use CLI features such as
pipes and redirection between
DOS and Windows NT. The
in NT and 2000 is similar, but no virtual machine is loaded: it is
handled by OS2SS.EXE and OS2.EXE.
64-bit versions of Windows do not support NTVDM and cannot run 16-bit
DOS applications directly; Third-party emulators such as DOSbox can be
used to run these programs.
DOS systems utilize a command line interface. Programs are started by
entering their filename at the command prompt.
DOS systems include
several programs as system utilities, and provides additional commands
that don't correspond to programs (internal commands).
In an attempt to provide a more user-friendly environment, numerous
software manufacturers wrote file management programs that provided
users with menu- and/or icon-based interfaces.
Microsoft Windows is a
notable example, eventually resulting in
Microsoft Windows 9x becoming
a self-contained program loader, and replacing
DOS as the most-used
PC-compatible program loader.
Text user interface
Text user interface programs included
DOS Navigator, Volkov Commander, Quarterdesk
DESQview, and Sidekick.
Graphical user interface
Graphical user interface programs included
Graphics Environment Manager
Graphics Environment Manager (originally written
for CP/M) and GEOS.
Eventually, the manufacturers of major
DOS systems began to include
their own environment managers. MS-DOS/IBM
DOS 4 included DOS
DR DOS 5.0, released the next year, included ViewMAX, based
Terminate and Stay Resident
Main article: Terminate and Stay Resident
DOS is not a multitasking operating system.
DOS did however provide a
Terminate and Stay Resident (TSR) function which allowed programs to
remain resident in memory. These programs could hook the system timer
and/or keyboard interrupts to allow themselves to run tasks in the
background or to be invoked at any time preempting the current running
program effectively implementing a simple form of multitasking on a
program-specific basis. The PRINT command did this to implement
background print spooling.
Borland Sidekick, a popup personal
information manager (PIM), also used this technique.
Terminate and Stay Resident programs were also used to provide
additional features not available by default. Programs like CED and
DOSKEY provided command line editing facilities beyond what was
available in COMMAND.COM. Programs like the
Extensions (MSCDEX) provided access to files on CD-ROM disks.
Some TSRs could even perform a rudimentary form of task switching. For
example, the shareware program Back and Forth (1990) had a hotkey
to save the state of the currently-running program to disk, load
another program, and switch to it, hence it was possible to switch
"back and forth" between programs, albeit slowly due to the disk
access required. Back and Forth could not enable background processing
however; that needed
DESQview (on at least a 386).
Further information: Category:
Arachne web browser
DOS was the dominant PC-compatible platform and many notable programs
were written for it. These included:
4DOS, a much improved replacement shell.
DOS web browser.
BASICA and GW-
BASIC replicate the BASIC
interpreter environment commonly found on 8-bit computers.
dBase, one of the earliest database programs.
DJGPP, the 32-bit DPMI
DOS port of gcc.
Harvard Graphics, one of the earliest presentation graphics design
Lotus 1-2-3, a protected mode spreadsheet program that saw heavy use
in corporate markets and has been credited with the success of the IBM
Microsoft Macro Assembler,
Microsoft C and
CodeView all part of
Microsoft development software.
Norton Commander and XTree, file management utilities.
Norton Utilities, a collection of disk and system utilities.
PC Tools, a collection of disk and system utilities.
PKZIP, the compression utility that quickly became the standard in
Qmodem and Telix, modem communication programs.
QEMM and 386MAX,
DOS memory management
DOS memory management utilities.
Sidekick, a popup personal information manager.
Turbo Pascal, Turbo BASIC,
Turbo C and
Turbo Assembler all part of
Borland's integrated development environment.
Vern Buerg's popular LIST utility, which displays the content of files
in ASCII or HEX.
WordPerfect, a word processor that is currently produced for the
WordStar, an early word processor which used unique control-key
sequences that were replicated by many other editors.
DOS operating systems
COMMAND.COM, the command line interpreter for
DOS and Windows 9x
VGA-compatible text mode, the base of DOS’s TUI on IBM PC
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DOS batch file programming handbook
Loadable kernel module
Process control block
Multilevel feedback queue
Shortest job next
Memory management and
General protection fault
Storage access and
Virtual file system
Virtual tape library
Classic Mac OS