DOS stands for Disk Operating System In general terms, DOS is a
command line interface (CLI) OS to manage data in disks. What we
have been accostumed to is DOS as the CLI OS for the IBM Personal
Computer and clones written by Tim Paterson and then sold by
Microsoft, on which Windows was later
Although IBM originally used the acronym DOS in the early 1970s
for their disk operating system for IBM
System/360, the 1970s version of DOS (later replaced by VSE) is not the same as what we commonly know
as DOS for IBM PC and clones.
In computer science, many terms are confusing and DOS is one of
them. If it is spelled DoS (lower case `o`), we
refer to denial of service. In this page, I am covering DOS (all
To make matters ever more confusing, one of the biggest
misconceptions nowadays is that we think of DOS and MS-DOS as a synonyms. In
reality, MS-DOS is
Microsoft's version of DOS.
In the early 1980s Microsoft bought the source code for 86-DOS
(commonly referred to Quick and Dirty Operating System, QDOS),
which was developed by Tim Paterson for the Intel 8086
microprocessor, for Seattle Computer Products (SCP). 86-DOS
contained about 4,000 lines of assembler. QDOS later became PC DOS for
the IBM Personal Computer system on August 1981. DOS was not
developed originally by Microsoft and Bill Gates (in his book The Road Ahead, 1995)
recognizes Tim Paterson as the father of DOS. Although Microsoft's
version of DOS (MS-DOS) has become obsolete, many DOS clones and OS
that can interpret DOS exist and are commonly used.
Nowadays, what is left of MS-DOS is reduced to a handful of files buried in
C:\WINDOWS\COMMAND in Windows
9x, C:\WINNT\SYSTEM32 in Windows NT
4 or C:\WINDOWS\SYSTEM32 in Windows NT
5 (XP) and up — not to be confused with PowerShell
(C:\WINDOWS\SYSTEM32\WINDOW~1\V1.0). I would like to see
DOS included back in Windows as a
stand-alone OS (similar to what macOS did with Unix). Worse of all, Windows NT
4 and up use an emulation of MS-DOS 5.0 (1991) — not 6.0 (1993) or 6.21/6.22
(1994) — that makes our life hell when trying to work with
old DOS commands and batches. Some of these commands do not work
anymore or exist anymore. Microsoft forces users to use the less
effective Windows 4.xx versions of programs
that were reliable in DOS.
MS-DOS as a
stand-alone OS (less than 5 MB in MS-DOS 6.22) has not been marketed by Microsoft, since
1994. Microsoft opted to concentrate on the Windows graphical OS project in 1983
(marketed against Steve Jobs' Apple Macintosh, 1984).
DOS originally included BASIC, which later became
QuickBASIC and then QBasic (QBASIC.EXE). Nowadays, Microsoft does not
include any programming language by default. QBASIC.EXE
has to be copied from D:\OTHER\OLDMSSDOS to
DOS Shell (230 KB) was last included in MS-DOS 6.2. Amazingly PC DOS Shell
was dropped around the same time.
The D:\OTHER\OLDMSSDOS (Old MS-DOS) directory on the Windows
95/98 disk has 17 files. Note that D: is your CD-ROM
drive and that there is no TREE, just DELTREE.
See directory below.
Maybe you can get your hands on any used copy of MS-DOS 5.0 (1991) or MS-DOS 6.22 (1994). Be
careful since Microsoft might consider the latter activity
illegal. You can download free of charge and use FreeDOS.
Installing MS-DOS on i386 & i486
This technique is different from what most nowadays books
indicate, using FAT16. The only drawback of installing FAT16 DOS
is that the HDD has to be divided into partitions not larger than
2 GB each (seen by the system as separate disks). The first
partition is primary and the rest are logical partitions.
You can also use a RAM drive (RAMDRIVE.SYS), which
will increase memory performance similar to paging. Since it is
not a physical disk, you should not save anything on it that you
really want to save.
These instructions cover MS-DOS only although they might also apply to DOS
clones. Reference to PC DOS 2000 is supplied. Unfortunately I do not
have experience on other versions of DOS like DR-DOS 7.03 (only
3.13 MB, 3 floppies), which is differently and not normally taught
The installation procedure, explained in this site, is
different from what most books might tell you. Both
CONFIG.SYS and AUTOEXEC.BAT are changed. RAM is
improved. By using this technique, a DOS and Windows set-up would work almost as
well as /swap in Unix.
Run FDISK.EXE from the boot disk.
View old partitions, if any, and delete them.
Delete first non-DOS partitions, then logical, then extended
and finally the primary (if any).
Make primary partition. Since MS-DOS has a FAT16 architecture, MS-DOS cannot read more than
2 GB at a time.
Make secondary partitions (less than 2 GB). On the secondary
partition, make logical partitions if needed. If the logical
partition is close or over 2 GB, make 1 GB partitions. Then
FORMAT each partition.
Make sure CONFIG.SYS recognizes as many logical
partitions as you need. The total number cannot exceed 26 logical
partitions (one for each letter of the English alphabet). Each
partition will be assigned a letter by MS-DOS.
Create backup files (.BAK) of CONFIG.SYS and
AUTOEXEC.BAT before doing changes. Should there be a
problem while booting, change CONFIG.BAK and
AUTOEXEC.BAK back to CONFIG.SYS and
AUTOEXEC.BAT accordingly. It is better to be safe than
Open CONFIG.SYS and AUTOEXEC.BAT with
EDIT on MS-DOS or E on PC DOS. Then save them with
the new names.
You may also copy them to new files with different names, of
At this point, you can create the RAM drive (or virtual disk)
that I mentioned before.
DEVICEHIGH=C:\WINDOWS\RAMDRIVE.SYS 2048 /E
Do changes on CONFIG.SYS by adding the following lines
to mount a CD-ROM in MS-DOS.
Then edit AUTOEXEC.BAT.
Copy AOATAPI.SYS to the HDD from MS-DOS. Both
CONFIG.SYS and AUTOEXEC.BAT need this file, so
copy it to your HDD.
A:\COPY AOATAPI.SYS C:
Run MEMMAKER (MS-DOS
6.x) to optimize memory management in MS-DOS. PC DOS does
not have MEMMAKER, but rather RAMBOOST, which
does a similar job, including EMM386.EXE to simulate
Reboot system pressing F8, which will let you confirm
each step of the CONFIG.SYS and AUTOEXEC.BAT. If
there is a problem, reboot system pressing F5 bypassing
CONFIG.SYS and AUTOEXEC.BAT. Change
CONFIG.BAK and AUTOEXEC.BAK to
CONFIG.SYS and AUTOEXEC.BAT. Repeat instructions
or throw these instructions away. Either way, it is still a fun
Make sure the BIOS will read CD-ROM first. Follow instructions
provided by the computer manufacturer.
Reboot system with the Windows CD-ROM or 3.5
floppies. If you are installing Windows
3.1 on an i386 or i486 PC, check out the Calmira shell.
Depending on your needs, you might need to
connect the system to a network (internet or LAN, most likely) or
not. If you do, you need to load to memory the correct packet
driver for the network interface card (NIC) on boot. Note that the
packet driver is a .COM file ending on
PD (for packet driver). Add the
following line to AUTOEXEC.BAT replacing
FOOBARPD.COM with the correct packet driver file
LH FOOBARPD.COM 0X60 5 0X300
In the example above, the first parameter (0X60) sets
the interrupt. The second one (5) sets the IRQ and the
last one (0X300) sets the I/O port.
Maintaining a Hard Drive Running MS-DOS &
I have put together a batch file (set of organized commands),
which will DEFRAG and SCANDISK your HDD. The
batch is compatible with i386 clones with DOS like FreeDOS. Keep in mind that you can only run
the batch in MS-DOS, not from Windows.
If you do not want to see the DOS commands while the batch file
is running, edit the batch turning ECHO off.
All files are randomly saved on your HDD. A practical way to
manage your HDD would be having all parts that form a file
together. DEFRAG organizes files fully (/F),
defragments (defrags) files leaving space between them
(/U), sorts them by extensions (/SE) and skips
using extended or upper memory (/SKIPHIGH).
DEFRAG /F/U/SE/SKIPHIGH C:
SCANDISK repairs problems that your all disks may have
automatically without prompting (asking), deletes errors, skips
summary and checks the surface the disk. This line of code might
not work with other distributions of DOS.
The batch creates (if not already created) and assigns
C:\TEMP as the temporary directory instead of using
C:\DOS or C:\WINDOWS as a temporary directory.
Some programs delete the temporary directories after installation.
This would be serious trouble if the installation routine deleted
the C:\DOS directory.
IF NOT EXIST C:\TEMP MKDIR C:\TEMP
If you are running Microsoft Office 6.0 or earlier, you might
want to delete all temporary files, which start with a tilde
DEL C:\~*.* /F/S/Q/A:R/A:H/A:S/A:A
Note that using the recursive switch (/S) in
DEL tells the system to delete a certain criteria (in
this example, ~*.*) in all subdirectories from a specific
starting point, (in this example, C:, meaning the whole
To delete any temporary files created by other programs, delete
by force the contents of the C:\TEMP directory and all
subdirectories without being prompted to confirm deletion,
regardless of their attributes.
DEL C:\TEMP\*.* /F/S/Q/A:R/A:H/A:S/A:A
If you want to generate a log of the deletions, send the output
to text file (for this example, FOO.TXT). In the example
below, the system will first write the date (%DATE%) and
time (%TIME%) when the batch is run and two blank lines
(ECHO., including the period after ECHO) after
the log has been generated for cosmetic purposes. As such, these
blank lines can be excluded.
ECHO %DATE% %TIME% > FOO.TXT
DEL C:\~*.* /F/S/Q/A:R/A:H/A:S/A:A > FOO.TXT
DEL C:\TEMP\*.* /F/S/Q/A:R/A:H/A:S/A:A > FOO.TXT
ECHO. > FOO.TXT
ECHO. > FOO.TXT
Putting all the commands together, your batch file would look
as the sample below.
Note that is good practice to leave blank lines between
sections of a batch file to make it easier to read. These lines do
not affect the functionality of the batch file (no speed increase
or delay). Therefore the sample above is the same as the one
below, but the one below is easier on the eyes.
Of course, follow this instructions at your own risk. Although
these commands will not normally hurt your system, do
NOT blame me as I take no responsibility if
something goes wrong and/or if you delete important data by
mistake. Refer to the disclaimer.
As I mentioned at the beginning of this section, these
instructions are for MS-DOS. Other versions of DOS are slightly different.
For example, FreeDOS has a
more organized directory structure and comes with
C:\FDOS\TEMP where FDOS is the DOS subdirectory.
I do not know if FreeDOS has a
built-in facility for garbage management. If you were to adapt the
previous code, make sure you understand the directory structure of
the version of DOS as well as which commands and executables are
Versions of DOS Compatible with MS-DOS:
DR-DOS (Digital Research)
DR-DOS was an alternative to MS-DOS and PC DOS during the DOS
heyday in the 1980s. It has changed owners in the past two
decades from Digital Research (DR) to Novel as Novel DOS (1991),
to Caldera as OpenDOS (1996), to DeviceLogics once again as
DR-DOS (2002). Since its last incarnation, DR-DOS/OpenDOS
Enhancement Project was started as a community initiative to
keep its open source up to date with
FreeDOS by Jim Hall is an x86 16/32-bit open sourceMS-DOS clone based on DOS-C (1994) by Pat
Villani that can "reproduce the functionality of MS-DOS.".
The directory structure of FreeDOS is based on Linux and all content of the OS is located in
C:\FDOS including the TEMP subdirectory
(C:\FDOS\TEMP, which is different from the path that I
have used since I learned to work with MS-DOS.
Within modern DOS clones, FreeDOS seems to be the most
popular, robust and most user-friendly choice. As a matter of
fact, it is my DOS of choice especially since Jim Hall is very
accessible for questions and continuously makes video tutorials
on his OS.
To install software, you can use FDIMPLES to access
its repository. To establishing network connections,
FDNET.BAT handles a vanilla packet driver.
NEWDOS (NewDOS or NEWDOS+>; not to be confused with New-DOS or NewDOS) was designed for TRS-80
series of computers.
NTFSDOS developed by System Internals (Winternals) allowed
users see NTFS partitions (NT 4/5 encrypted
partitions) as regular DOS FAT16 partitions. To no one's
surprise, if NTFSDOS could break Microsoft's encryption in order
to access a drive as plain DOS, Microsoft was bound to acquire it
and remove it from the market (2006).
NX-DOS is an x32 16-bit/32-bit MS-DOS clone that uses RX-DOS memory management.
PC DOS (International Business Machines)
DOS is made by IBM. It is more reliable than Microsoft's
latest commercial version (MS-DOS 6.22). IBM indicates that PC DOS 2000
can give users an additional 40 KB of free disk space. There is
further information on PC DOS 7. Also refer to the batch to maintain your HDD running on MS-DOS or PC DOS.
PTS-DOS "is a powerful and fastest DOS with a simple
graphical file manager and FAT32 architecture. PhystechSoft also
ROM-DOS includes Borland SDK and is "much more than an
inexpensive replacement for MS-DOS, designed for embedded and mobile computing
environments" with access to FAT32.
Versions of DOS Incompatible with
Apple DOS was Apple's OS for Apple II (1977). It was replaced
by ProDOS (1983), related to Sophisticated Operating System
Atari DOS was the OS for Atari 8-bit home computers
(1979-1982). Various versions were available in the market by
Commodore DOS (CBM DOS) was a beast of its own running from
ROM for the MOS 6502 family of chipsets — from PET
(1977) to C128 (1985). The most commonly used version was 2.0
that came in the C64.
DOS/VSE is "DOS then DOS/VS then DOS/VSE then
VSE/SP then VSE/ESA (current) mainframe OS from 1964 till
today [which] has its own half dozen file systems neither
FAT16/FAT32 nor NTFS, not Linux compatible"
RX-DOS (with only eight
files) supports FAT12, FAT16 and FAT32. RX-DOS does not
support Windows and may support Linux. The OS has some bugs.
MS-DOS Emulators (Command Prompt
4DOS was a MS-DOS 5.0 emulator and COMMAND.COM
replacement by JP Software. Nowadays
the vendor markets its CMD.EXE replacement for Windows NT named Take Command
DOSBox is a MS-DOS 5.0 emulator released in 2002 for
BeOS (Haiku nowadays) FreeBSD, Linux, macOS, OS/2, RISC OS,
Solaris, and especially Windows. Since its
source code is available to install DOSBox. In theory, it can be
ported to any OS. Since old DOS programs (even those written
(coded) by Microsoft) may not run properly or at all in new
versions of Windows, DOSBox is
a practical tool, not only to run DOS games (not limited to
abandonware) as marketed by the developers.
Note that this emulator runs from the Z: virtual
disk (virtual disk) as seen below.
In order to access any files system, DOSBox needs the
directories to be mounted in order to access them (similar to Unix).
MOUNT X X:\GAMES
The latter command can be added after the line
[autoexec] in the DOSBOX.CONF, which serves as
both CONFIG.SYS and AUTOEXEC.BAT. Whether
mounting the subdirectory every time you need it or calling it
from DOSBOX.CONF, at that point, go to the new virtual
disk (X:) in order to access the contents of the
mounted directory (X:\GAMES) as normally done in most
Just as with a real AUTOEXEC.BAT, the
[autoexec] section in the DOSBOX.CONF file,
you can call commands turning ECHO off.
MOUNT X X:\GAMES
The latter was quoted from the output of the HELP
DOSEMU is a command prompt
emulator "and is a Linux application that enables
Linux to run many DOS programs —
including some DPMI [DOS Protected Mode Interface
applications]" as per the project developers.
DOSEMU "uses FreeDOS as the default DOS". Therefore it
comes with the FreeCOM shell, a replacement for
DOSEMU mounts A: to access the floppy (B:
reserved for second floppy), C: to access the DOSEMU
environment acting as the OS including programs you install like
OpenGEM in my example, D:
to access the Linux home directory
(~\), E: to access the CD-ROM, Z:
where DOSEMU and all its commands reside.
The following was quoted from help.
XTM PC Emulator
XTM PC Emulator is
"a software emulation of a classic PC/XT computer [PC
DOS 3.0] for EPOC32." Within this standard
application for your portable computer, you can run any software
which would run on a low-end PC clones from the 1980s.
Graphic User Interfaces for MS-DOS Other Than
Since nowadays most of us are used to some GUI
or another, a good idea is installing OpenGEM (an modern and open source version of GEM), which is based on
FreeGEM, which is based on Graphical Environment Manager (GEM),
on MS-DOS or any
compatible clone like FreeDOS. If you decide to do
this on DOSBox, keep in mind that the installation path should
be on C:. You would need the path where you want to
mount OpenGEM to be installed.
MOUNT C X:\OpenGEM
Once installed, GEM.BAT can be ran from the
C: virtual disk. As mentioned before, you can edit
DOSBOX.CONF to mount the location of the
GEM.BAT as C: (unsure if it could run properly
if mounted using a different letter). You can even call
GEM.BAT to make OpenGEM run automatically, but image
guess that would take the fun out of running DOSBox.
There was a SourceForge project named BlueGEM that
combines FreeDOS with
FreeGEM in one package for DOS gamers. It was a great idea to
revive many old i386 and i486 PCs. The installations was be done
from a floppy so you had to mount the of the directory
containing the installation files to A:.
MOUNT A X:\[path]
Then run the INSTALL.APP, which calls
INSTALL.TXT to copy the installation files
Note that applications in GEM (FreeGEM and OpenGEM) are
.APP files — not DOS or Windows.EXE or .COM files.
Using the example above, on Linux, I
installed DOSBox running OpenGEM, various applications from the
OpenGEM SDK and ZSNES for DOS. I do not think there is anything
practical doing this, but it is sure fun to see old technology
originally written (coded) several decades ago running on new
hardware. It is merely an excuse to show off. After all, ZSNES
is also available on Linux.
Note that, on Windows, you can
run the PortableApps.com
port of DOSBox making it ready from a USB flash drive with any
added software and/or your personalized configuration.