Episode 85 – 86 – 87 MS DOS

Dedicated to Little Pocok

MS DOS acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and some operating systems attempting to be compatible with MS-DOS, are sometimes referred to as “DOS” (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatible personal computers during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system.

IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax, and capabilities.

During its lifetime, several competing products were released for the x86 platform and MS-DOS went through eight versions, until development ceased in 2000. Initially, MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately, it was the key product in Microsoft’s development from a programming language 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.



MS-DOS was a renamed form of 86-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 IBM Personal Computer hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for US$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, which, in August 1981, offered it as PC DOS 1.0 as one of three operating systems for the IBM 5150, or the IBM PC

Within a year, Microsoft licensed MS-DOS to over 70 other companies. 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 (the DOS BIOS), 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. The company planned, over time, to 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”. 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. 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. Microsoft would later re-license the code under the MIT License on September 28, 2018, making these versions free software.

As an April Fool’s Day 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.


Microsoft licensed or released versions of MS-DOS under different names like Lifeboat Associates “Software Bus 86” a.k.a. 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.)

In the former Eastern bloc, MS-DOS derivatives named DCP (Disk Control Program [de]) 3.20 and 3.30 existed in the late 1980s. They were produced by the East German electronics manufacturer VEB Robotron.

Only to mention some notable versions…

MS-DOS 1.x

DOS 1.x was very limited in what it could do. It could start applications (.COM and .EXE), and process batch files (.BAT). DOS 1.0 worked with 160KB floppies and did not support folders (all files had to be in the root). The command interpreter supported the following commands:


No pipes, redirection, or device drivers were supported. The DOS API in 1.0 was very limited.

MS-DOS 1.25, the equivalent of PC-DOS 1.10, was the first version licensed to OEMs beyond IBM or Seattle Computer Products.

Some vendors labeled their versions of MS-DOS with different names and version numbers. All of the versions here are believed to be based off of MS-DOS 1.25, even if the vendor called it something else.

  • Version 1.10 (OEM) – possible basis for IBM’s Personal Computer DOS 1
  • Version 1.11 (OEM) – possible basis for IBM’s Personal Computer DOS 1.0
    • Compaq-DOS 1.12, a Compaq OEM version of MS-DOS (1.25 or higher)
  • Version 1.14 (OEM) – possible basis for IBM’s Personal Computer DOS 1.0
    • Zenith Z-DOS 1.19, a Zenith OEM version of MS-DOS (1.25 or higher)
  • 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

MS-DOS 2.x

Adds support for 5.25 inch 260kb floppy drives, user installable device drivers and the first version to support folders and tree structurable file system.

MS-DOS 3.x

DOS 3.0 adds support for FAT16 partitions up to 32MB, 1.2MB floppy drives, and the IBM AT internal clock.

MS-DOS 3.0x is extremely rare. After the release of IBM PC-DOS 3.0, Microsoft dragged their feet providing MS-DOS 3.x to other OEMs, possibly to appease IBM. Most OEMs didn’t get MS-DOS 3.x until 3.1.

Apricot and Compaq MS-DOS 3.0x versions are known to exist. Zenith and AT&T are suspected to exist.

MS-DOS 3.20 is the first release offered as a “vanilla” boxed set directly to consumers, instead of just OEMs.

MS-DOS 3.30 was a very popular version of MS-DOS. Due to the problems with 4.0, and 3.31 only being available via OEM, many users stuck with 3.30 unless they needed larger hard drive support.

MS-DOS 3.31 was only sold through a few OEMs, mainly Compaq.

This version adds support for hard drives up to 512MB.

It also does not use as much conventional memory as DOS 4.x or later, making it a good choice for 8088/8086 based computers.

  • Version 3.0 (OEM) – 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 3.22 (OEM) – (HP 95LX)
  • Version 3.3 (OEM) – First version to support 3.5-inch, 1.44 MB floppy drives and diskettes (OEM)
  • Version 3.31 (OEM) – supports FAT16B and larger drives

MS-DOS 4.0

MS-DOS 4 added support for hard drive partitions up to 2GB. It used much more of the base 640K, and was somewhat buggy.

Microsoft had long planned that MS-DOS “4” would be a multitasking-capable operating system, but IBM had insisted on creating a new version of regular DOS for use with their PS/2 computers. The below versions, as released to the consumer market, are based on DOS 3.3x and IBM’s PC-DOS 4.0 enhancements. Although essentially scrapped, some narrow European markets did receive Microsoft’s Multitasking MS-DOS 4.0

Microsoft’s initial 4.00 release (File dates 10/6/1988) was quickly followed up by 4.01, making this an uncommon version. To add to the confusion, most OEMS badged their 4.01 disks as “4” or “4.0”.

Includes a graphical/mouse interface. It had many bugs and compatibility issues.

  • 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 GB
  • 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 and when using SYS to make a floppy disk or a partition of a hard drive bootable).
  • Version 4.01a (OEM)

MS-DOS 5.0

MS-DOS 5 introduced numerous new features and was a flagship release for Microsoft. A full screen text editor EDIThas replaced the former line editor EDLIN supplied since the early days of DOS. Microsoft QBasic also shipped in DOS 5 replacing GW-BASIC. MS-DOS 5 also supported 2.88MB 3.5″ floppy disks as well as hard disks up to 2GB in size. The memory management was rewritten to allow DOS to utilize the High Memory Area and Upper Memory Area to reduce its usage of conventional memory. Numerous bugs were noticed shortly after launch which lead to the 5.0a update.

Added by Andriy27314 Posted in MS-DOS Version History

This release of DOS was the last of the collaboration between Microsoft and IBM and as a result will be the last result where PC-DOS and MS-DOS are near-identical. This was also the version of DOS used in the OS/2 and Windows NT virtual DOS machine.

When MS-DOS 5 was released the entire market had become dominated by IBM and compatible systems, so specific OEM versions of DOS for machines not using an IBM BIOS were not shipped as in prior releases.

  • 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. Hard disk partitions greater than 32 MiB and up to a maximum size of 2 GB was now provided by the MS-DOS kernel.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
  • 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

MS-DOS 6.x

MS-DOS 6.0 includes many new utilities and features, including a disk defragmenter, disk compression, anti-virus, a new backup system, and pc-pc file transfer tools. It was heavily criticized as buggy by the media, primarily due to file corruption issues with DoubleSpace and the lack of tools to repair such issues.

Note that the boot sector OEM ID of “MSDOS6.0” is correct and genuine. Microsoft reverted to using “MSDOS5.0” on later disks.

Microsoft intentionally skipped “6.1” to prevent confusion with IBM’s independently produced PC-DOS 6.1. Microsoft also made a free/inexpensive 6.0 -> 6.2 step up kit available.

This update corrects some major bugs in DoubleSpace, introduces ScanDisk, adds automounting of compressed floppies, and a tool to uncompress DoubleSpace compressed drives.

MS-DOS 6.21
This version was specifically released to remove DoubleSpace due to legal injunction. Their replacement “DriveSpace” was not yet ready.

MS-DOS 6.22
Microsoft DOS 6.22 was the last standalone version from Microsoft. It was also the last from Microsoft to run on an 8088, 8086, or 286.

6.22 adds DriveSpace, a replacement for DOS 6.20’s DoubleSpace drive compression that was removed in 6.21.

There’s a really detailed tutorial located at http://legroom.net/howto/msdos that gives tips on how to customize DOS. We suggest you follow this tutorials suggestions for setting up and customizing DOS. However, if you’re installing to a virtual machine, writing the disk images to actual floppies isn’t really necessary.

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.

Under the Microsoft Windows era

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.x

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.

Localized Versions

Localized versions of MS-DOS existed for different markets.[69] 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.

Notable MS DOS Applications
( there were so many … )

A System or Operating System / Platform / Architecture is only as good as the Applications available for it.

Text Editors and Office Suites

WordStar - Wikipedia
Wordstar under MS-DOS ( George RR Martin uses Wordstar 4.0)

wp62 font dialog
Corel Wordperfect 6.2 https://thewanderingnerd.wordpress.com/2015/04/19/corel-wordperfect-6-2-for-dos-a-look-back/

Dinosaur Sightings: Lotus Symphony 3.0 - Page 12 - TechRepublic
Lotus Symphony 3.0 for DOS

Microsoft Works 2.0 for DOS

Spreadsheets and Databases

WinWorld: Screenshots for Lotus 1-2-3 2.x (DOS)
Lotus 1-2-3 2.x for DOS – winworldpc.com
File:DBase III r1.0 - Edit.png - Wikimedia Commons
dBase III
Multiplan on DOS
Multiplan under MS-DOS

Development Tools

Turbo CPP 3.0 - About
Turbo C++ 3.0 ( Aimed for the Home Market) – winworldpc.com
Borland CPP 3.1 - DOS IDE
Borland C++ 3.1 (Aimed for the Professional Market) – winworldpc.com

WinWorld: Screenshots for Borland Turbo Pascal 7.x
Borland Turbo Pascal 7.0 – winworldpc.com – I remember We did learn some / little Turbo Pascal in High School. No C++ tough 🙁

File Management

WinWorld: Screenshots for Norton Commander 5.5x
Norton Commander 5.5


On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether QDOS was more or less plagiarized from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft’s licensing requirements, but at a higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; many applications were sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS originally supported the simple .COM, which was modeled after a similar but binary-incompatible format known from CP/M-80. CP/M-86 instead supported a relocatable format using the file extension .CMD to avoid name conflicts with CP/M-80 and MS-DOS .COM files. MS-DOS version 1.0 added a more advanced relocatable .EXE executable file format.

Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in. Users who began using MS-DOS with their machines were compelled to continue using the version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system.

In the business world the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix.

In the emerging world of home users, a variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II, early Apple Macintosh, the Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with the PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had a large share of the business computer market.

Microsoft and IBM together began what was intended as the follow-on to MS-DOS/PC DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that “DOS is Dead” and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking (as was available in operating systems since 1963) and offered a number of advanced features that had been designed together with similar look and feel; it was seen as the legitimate heir to the “kludgy” DOS platform.

MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft’s other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, Stacker disk compression, and others.

During the period when Digital Research was competing in the operating system market some computers, like Amstrad PC1512, were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus, which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format.

While OS/2 was under protracted development, Digital Research released the MS-DOS compatible DR DOS 5.0, which included features only available as third-party add-ons for MS-DOS. Unwilling to lose any portion of the market, Microsoft responded by announcing the “pending” release of MS-DOS 5.0 in May 1990. This effectively killed most DR DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR DOS 6.0, which sold well until the “pre-announcement” of MS-DOS 6.0 again stifled the sales of DR DOS.

Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty, and doubt) regarding DR DOS. For example, in October 1990, shortly after the release of DR DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week. Brad Silverberg, then Vice President of Systems Software at Microsoft and general manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics (“to serve our customers better, we decided to be more forthcoming about version 5.0”) and denying that Microsoft copied features from DR DOS:

“The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn’t be surprising that DRI has heard some of the same requests from customers that we have.” – (Schulman et al. 1994).

The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft’s further contributions to OS/2 also went into creating a third GUI replacement for DOS, Windows NT.

IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows.

Legal Issue

As a response to Digital Research’s DR DOS 6.0, which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac was unwilling to meet Microsoft’s terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft’s DoubleDisk, using it as the core for its DoubleSpace disk compression.[71]

MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code.

Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft’s licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages in the Caldera v. Microsoft lawsuit. It was believed that the settlement ran in the order of $150 million, but was revealed in November 2009 with the release of the Settlement Agreement to be $280 million.

MS DOS modern alternatives


FreeDOS | The FreeDOS Project

Freedos is still available today and actively developed. Can install it on Virtuablox or on bare metal.

4DOS (4OS2 – OS/2 Version as well and 4NT – 4DOS for WindowsNT)

4DOS — Vikipēdija


Interesting Fact / Add-on:

4NT’s TCI – Take Command Interface still exists today as JP Software’s TC (TCI + TCC)

4NT – Copyright http://www.fileflash.com

This program allowed one to attach (thereby reducing screen clutter) and detach tabbed consoles to a single window. This program requires Windows XP or later.

A new version of Take Command extends the original Tabbed Command Interface, expanded with extra windows to allow input to be composed, to graphically navigate directories and files, and extra features. 4NT is bundled as Take Command Console. A light feature-reduced version of TCC is released as a free download.

JP Software then released:

  • TC (full pack of TCI + TCC)
  • TCLE (TCI + TCC/LE) – Full Pak with TCC/LE formerly known as 4NT ( free unsupported version)
  • TCC (just the command utility)
  • TCC/LE – TCC/LE formerly known as 4NT ( free unsupported version)

Dosbox / DOSEMU

DOSBox in DOSBox: dosbox
DOSBox running under Windows

DOSEmu - For Linux
DOS Emulator

Using MS DOS ( or its alternatives) Today

You can install FreeDOS on bare metal or in Virtualbox/Vmware as a VM or 4DOS or other DOS Emulators like Dosbox / DOSEMU or alternatives under most other operating systems: Windows, Linux, Mac. Solaris 10 SPARC even has a working DOSBOX binary ( does not play nice with the Sun keyboard and it should be built with some extra config flags so it is solved but works fine via ssh -X with X11Forward and as long as its not very graphics intensive application ( like a game sensitive to FPS) I can run it just fine.)

Dosbox , vDOS , DOSEMU or alternatives can be a quick and dirty/easy way to get up and running quick to run your favourite DOS programs from the era.

True Die Hard Fans are building retro computers or purchasing retro battlestations which are era-appropriate and as a result can find a 486 desktop computer for a price of a new laptop sometimes on sites like ebay. — Remember Old Hardware many times can come with failed or failing parts which might not be easy to source and sometimes even replace them can be a challange ( if you have the skills and you are up to it)

I agree some of them look so good you want to have them. 🙂

Scan from one of the only brochures marketing the Compaq 486c – as you can see, the selling points were the display and the CPU performance. https://www.retropaq.com/the-compaq-portable-486/
Compaq Presario 850  Series 3410 486 Tower Computer
Compaq Presario 850 Series 3410 486 Tower Computer

Use of Undocumented APIs

As a response to Digital Research’s DR DOS 6.0, which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac was unwilling to meet Microsoft’s terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft’s DoubleDisk, using it as the core for its DoubleSpace disk compression.[71]

MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code.

Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft’s licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages in the Caldera v. Microsoft lawsuit. It was believed that the settlement ran in the order of $150 million, but was revealed in November 2009 with the release of the Settlement Agreement to be $280 million.

Windows Command Line Interface

All versions of Microsoft Windows have had an MS-DOS or MS-DOS-like command-line interface (CLI) called MS-DOS Prompt which redirected input to MS-DOS and output from MS-DOS to the MS-DOS Prompt, or, in later versions, Command Prompt. This could run many DOS and variously Win32, OS/2 1.x and POSIX command-line utilities in the same command-line session, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOS interface. It is to be noted that the Command Prompt introduced with Windows NT is not actually MS-DOS, rather a CLI which shares some commands with MS-DOS.

Command Prompt in Windows 10

Earlier Versions of Windows

The 16-bit versions of Windows (up to 3.11) ran as a Graphical User Interface (GUI) on top of MS-DOS. With Windows 95, 98, 98 SE and Me, the role of MS-DOS was reduced to a boot loader, with MS-DOS programs running in a virtual DOS machine within 32-bit Windows, with ability to boot directly into MS-DOS retained as a backward compatibility option for applications that required real mode access to the hardware, which was generally not possible within Windows.[73] The command line accessed the DOS command line (usually COMMAND.COM) through a Windows module (WINOLDAP.MOD).

MS-DOS Prompt in Windows 95

Windows NT

Windows NT based operating systems boot through a kernel whose sole purpose is to load Windows. One cannot run Win32 applications in the loader system in the manner that OS/2, UNIX or Consumer Windows can launch character-mode sessions.

The command session permits running of various supported command-line utilities from Win32, MS-DOS, OS/2 1.x and POSIX. The emulators for MS-DOS, OS/2 and POSIX use the host’s window in the same way that Win16 applications use the Win32 explorer. Using the host’s window allows one to pipe output between emulations.

The MS-DOS emulation takes place through the NTVDM (NT Virtual DOS Machine). This is a modified SoftPC (a former product similar to VirtualPC), running a modified MS-DOS 5 (NTIO.SYS and NTDOS.SYS). The output is handled by the console DLLs, so that the program at the prompt (CMD.EXE, 4NT.EXE, TCC.EXE), can see the output. 64-bit Windows does not have either the DOS emulation, or the DOS commands EDIT, DEBUG, EDLIN), that come with 32-bit Windows.

The DOS version returns 5.00 or 5.50, depending on which API function is used to determine it. Utilities from MS-DOS 5.00 run in this emulation without modification. The very early beta programs of NT show MS-DOS 30.00, but programs running in MS-DOS 30.00 would assume that OS/2 was in control.

The OS/2 emulation is handled through OS2SS.EXE and OS2.EXE, and DOSCALLS.DLL. OS2.EXE is a version of the OS/2 shell (CMD.EXE), which passes commands down to the OS2SS.EXE, and input-output to the Windows NT shell. Windows 2000 was the last version of NT to support OS/2. The emulation is OS/2 1.30.

POSIX is emulated through the POSIX shell, but no emulated shell; the commands are handled directly in CMD.EXE.

The Command Prompt is often called the MS-DOS prompt. In part, this was the official name for it in Windows 9x and early versions of Windows NT (NT 3.5 and earlier), and in part because the SoftPC emulation of DOS redirects output into it. Actually only COMMAND.COM and other 16-bit commands run in an NTVDM with AUTOEXEC.NT and CONFIG.NT initialisation determined by _DEFAULT.PIF, optionally permitting the use of Win32 console applications and internal commands with an NTCMDPROMPT directive.

Win32 console applications use CMD.EXE as their command prompt shell. This confusion does not exist under OS/2 because there are separate DOS and OS/2 prompts, and running a DOS program under OS/2 will launch a separate DOS window to run the application.

All versions of Windows for Itanium (no longer sold by Microsoft) and x86-64 architectures no longer include the NTVDM and can therefore no longer natively run DOS or 16-bit Windows applications. There are alternatives in the form of virtual machine emulators such as Microsoft’s own Virtual PC, as well as VMware, DOSBox, and others.

End of Life

The introduction of Windows 3.0 in 1990, with an easy-to-use graphical user interface, marked the beginning of the end for the command-line driven MS-DOS. With the release of Windows 95 (and continuing in the Windows 9x product line through to Windows Me), an integrated version of MS-DOS was used for bootstrapping, troubleshooting, and backwards-compatibility with old DOS software, particularly games, and no longer released as a standalone product.[74] In Windows 95, the DOS, called MS-DOS 7, can be booted separately, without the Windows GUI; this capability was retained through Windows 98 Second Edition. Windows Me removed the capability to boot its underlying MS-DOS 8.0 alone from a hard disk, but retained the ability to make a DOS boot floppy disk (called an “Emergency Boot Disk”) and can be hacked to restore full access to the underlying DOS. On December 31, 2001, Microsoft declared all versions of MS-DOS 6.22 and older obsolete and stopped providing support and updates for the system.[75] As MS-DOS 7.0 was a part of Windows 95, support for it also ended when Windows 95 extended support ended on December 31, 2001.[76] As MS-DOS 7.10 and MS-DOS 8.0 were part of Windows 98 and Windows ME respectively, support also ended when Windows 98 and ME extended support ended on on July 11, 2006, thus ending support and updates of MS-DOS from Microsoft.

In contrast to the Windows 9x series, the Windows NT-derived 32-bit operating systems (Windows NT, 2000, XP and newer), developed alongside the 9x series, do not contain MS-DOS compatibility as a core component of the operating system nor do they rely on it for bootstrapping, as NT was not with the level of support for legacy MS-DOS and Win16 apps that Windows 9x was,[74] but does provide limited DOS emulation called NTVDM (NT Virtual DOS Machine) to run DOS applications and provide DOS-like command prompt windows. 64-bit versions of Windows NT do not provide DOS emulation and cannot run DOS applications natively.[78] Windows XP contains a copy of the Windows Me boot disk, stripped down to bootstrap only. This is accessible only by formatting a floppy as an “MS-DOS startup disk”. Files like the driver for the CD-ROM support were deleted from the Windows Me bootdisk and the startup files (AUTOEXEC.BAT and CONFIG.SYS) no longer had content. This modified disk was the base for creating the MS-DOS image for Windows XP. Some of the deleted files can be recovered with an undelete tool.[79] When booting up an MS-DOS startup disk made with Windows XP’s format tool, the version number and the VER internal command reports as “Windows Millennium” and “5.1” respectively and not “MS-DOS 8.0” (which was used as the base for Windows Me but never released as a stand-alone product), though the API still says Version 8.0.

When creating a DOS startup disk on Windows Vista, the files on the startup disk are dated April 18, 2005 but are otherwise unchanged, including the string “MS-DOS Version 8 Copyright 1981–1999 Microsoft Corp” inside COMMAND.COM. Windows 7, 8, and 8.1 can also create a MS-DOS startup disk. Starting with Windows 10, the ability to create a DOS startup disk has been removed and so either a virtual machine running MS-DOS or an older version (in a virtual machine or dual boot) must be used to format a floppy disk, or an image must be obtained from an external source. Other solutions include using DOS compatible alternatives, such as FreeDOS or even copying the required files and boot sector themselves. With Windows 11, the operating system does not support NTVDM as it’s only 64-bit, thus removing any remaining support for MS-DOS or it’s applications from Microsoft.

MS-DOS 6.22 was the last standalone version produced by Microsoft for Intel 8088, Intel 8086, and Intel 80286 processors, which remain available for download via their MSDN,[80] volume license, and OEM license partner websites, for customers with valid login credentials. MS-DOS is still used in embedded x86 systems due to its simple architecture and minimal memory and processor requirements, though some current products have switched to the still-maintained open-source alternative FreeDOS.

In 2018, Microsoft released the source code for MS-DOS 1.25 and 2.0 on GitHub. The purpose of this, according to Microsoft, is mainly for education and experimentation with historic operating systems and for new programmers to gain an understanding of how low-level software works, both historic and current. According to program manager Rich Turner, the other versions could not be open-sourced due to third-party licensing restrictions.[81]

Due to the historical nature of the software, Microsoft will not accept any pull requests to the code; only pull requests for modified and translated documentation will be accepted. Users, however, are allowed and fully encouraged to fork the repository containing the MS-DOS source code and make their own modifications, and do whatever they like with it.

Legacy Compatibility

From 1983 onwards, various companies worked on graphical user interfaces (GUIs) capable of running on PC hardware. However, this required duplicated effort and did not provide much consistency in interface design (even between products from the same company).

Later, in 1985, Microsoft Windows 1.0 was released as Microsoft’s first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS. At first Windows met with little success, but this was also true for most other companies’ efforts as well, for example GEM. After version 3.0, Windows gained market acceptance.

Windows 9x used MS-DOS to boot the Windows kernel in protected mode. Basic features related to the file system, such as long file names, were only available to DOS applications when running through Windows. Windows NT runs independently of DOS but includes NTVDM, a component for simulating a DOS environment for legacy applications.

Closing Thoughts

I like especially the era of the 80s and 90s of computing and the home computer boom which occurred throughout the world. OK , fair enough I was born in ’82 and it left me with no choice in the matter. But I have always thought it was a conscious decision form my part.

The speed and leaps computing evolved at those times when it came to hardware or software was something magical.Each month and year brought something significant , something new , something we thought just some time ago that it can not be done or seemed impossible to achieve.

Performance , disk space , new peripherals
usenet, bbs then the internet and email and the rest became history

One particular part I really miss and love about this era that computers could and were important tools which let you focus on the task at hand you had to handle without distractions. Think of word processors or office suites applications for handling spreadsheets or making a presentation or write a program.

No ads, nagging updates and not another 300x popups and messages from various parts of the system and from other applications ( you did not even realized before those things were your computer ) or system updates trying to take your attention away from what You were actually doing just a minute ago.

In this sense the 80s always reminds me this era of simplicity like a typewriter. The beauty in doing less or sometimes only a single function ( perhaps at a time…) but letting you immerse in that experience and focus and concentrate.

Today the user interfaces are so colorful it sometimes becomes a distraction so many things trying to grab my attention like I mentioned. It can be very overwhelming very quickly. Messages, popups, notifications, ads, more ads…. ah.

When All I want sometimes is to achieve one single thing:
being it writing my thoughts down or to do a presentation , perhaps make some simple calculations or just one and only one task at a time but to do it well.

There is beauty in simplicity and being distraction free.

This is the reason I like to just go back sometimes into MS-DOS and bring up one single application at a time and just use it to do one single thing and not let anything else taking me away from that….

It also reminds me of Modern Cars Vs Classic Cars 🙂










The Server Room Show – Episode 67 – 68 AIX


I have always liked Operating Systems. They make computers become something usable and something you can actually interact with to do things Vs what they are in reality which is just a bunch of electronic parts shoved together in some pretty box.

While growing up I have been exposed to the Home Computer boom which was at its height during the 80s with iconic members like the Commodore 64 and some Z80 Clones like the HT-1080Z which were available at high schools during 1983 – 1986 my infancy in Hungary (see the links on the bottom and the image below).

I do still remember the first time somewhere around the late ’87-’88 when I first had the opportunity to touch one HT-1080Z and play with in a high school where my father worked at that time and He took me one early morning with him.

The HT-1080Z was built by Hiradastechnika Szovetkezet after purchasing the license for the Hong Kong based EACA company’s Video Genie computer which looks identical to the HT-1080Z. The Video Genie version sold in North American was called the PMC-80.

The Video Genie itself was considered a TRS-80 Model I clone although the two had hardware and software differences.

HT-1080Z School Computer (1983) – Péter Hoványi

I saw Commodore’s Basic, MS DOS and later on and some Novell Netware, Windows 3.1, OS/2 , BeOS, Linux, Mac OS, BSD then FreeBSD as I grew older.

It was during that time I have seen once a Pegasos motherboard/system running Amiga OS with true multitasking and multimedia which was very unique and not affordable to me at all and to this day I have never forgot the experience or the way it made me smile 🙂

But I have only heard about but never had any experience or exposure to z/OS, z/VM from IBM or UNIX of any kind (HP-UX, Solaris, AIX ) They were all very mystical and unreachable for me while I was a kid and even later when I was in my way through adulthood.

When eventually I became an IT Professional I though I would get exposure to all of these systems I have lusted after to know more about for years and years but the sad truth is that I have never had any well not at my jobs.

With the advent of virtualization and cloud computing these things are somewhat changing now but still it is not easy and most of the time not free to tinker around with these systems even just for your own amusement or educational reasons to pick some new or old knowledge up.

Big companies like IBM (AIX and z/OS) and HP (with HP-UX or OpenVMS) are not on the forefront to accommodate homelabbers ( hobbyist) with ways to run these systems for free for non-profit and home use in their home labs. There are some options open to partners and developers through business contracts for huge amounts of money per year which I’m sure no single individual can spare ( the realms of 5 – 10 thousands of euros).

Shows this nothing better than after many years of successful running HP is discontinuing the OpenVMS hobbyist license for individuals on the 31st of December 2021. It will mark an end of an era.


AIX (Advanced Interactive eXecutive) is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. Originally released for the IBM RT PC RISC workstation, AIX now supports or has supported a wide variety of hardware platforms, including the IBM RS/6000 series and later POWER and PowerPC-based systems, IBM System i, System/370 mainframes, PS/2 personal computers, and the Apple Network Server.

AIX is based on UNIX System V with 4.3BSD-compatible extensions. It is one of four commercial operating systems that have versions certified to The Open Group’s UNIX 03 standard (the others being macOS, HP-UX and eulerOS).

The AIX family of operating systems debuted in 1986, became the standard operating system for the RS/6000 series on its launch in 1990, and is still actively developed by IBM. It is currently supported on IBM Power Systems alongside IBM i and Linux.

AIX was the first operating system to have a journaling file system, and IBM has continuously enhanced the software with features such as processor, disk and network virtualization, dynamic hardware resource allocation (including fractional processor units), and reliability engineering ported from its mainframe designs


As we saw on the episode of UNIX on this podcast Unix started life at AT&T’s Bell Labs research center in the early 1970s, running on DEC minicomputers. By 1976, the operating system was in use at various academic institutions, including Princeton, where Tom Lyon and others ported it to the S/370, to run as a guest OS under VM/370. This port would later grow out to become UTS a mainframe Unix offering by IBM’s competitor Amdahl Corporation. IBM’s own involvement in Unix can be dated to 1979, when it assisted Bell Labs in doing its own Unix port to the 370 (to be used as a build host for the 5ESS switch’s software). In the process, IBM made modifications to the TSS/370 hypervisor to better support Unix.

It took until 1985 for IBM to offer its own Unix on the S/370 platform, IX/370, which was developed by Interactive Systems Corporation and intended by IBM to compete with Amdahl UTS. The operating system offered special facilities for interoperating with PC/IX, Interactive/IBM’s version of Unix for IBM PC compatible hardware, and was licensed at $10,000 per sixteen concurrent users

AIX version 1

AIX Version 1, introduced in 1986 for the IBM RT PC workstation, was based on UNIX System V Releases 1 and 2. In developing AIX, IBM and Interactive Systems Corporation (whom IBM contracted) also incorporated source code from 4.2 and 4.3 BSD UNIX.

The IBM RT PC Workstation

IBM PC RT 6151
IBM RT PC 6151 booting AIX 2.2.1

The IBM RT PC (RISC Technology Personal Computer) is a family of workstation computers from IBM introduced in 1986.

These were the first commercial computers from IBM that were based on a reduced instruction set computer (RISC) architecture. The RT PC used IBM’s proprietary ROMP microprocessor, which commercialized technologies pioneered by IBM Research’s 801 experimental minicomputer (the 801 was the first RISC). The RT PC ran three operating systems: AIX, the Academic Operating System (AOS), or Pick.

The RT PC’s performance was relatively poor compared to other contemporary workstations and it had little commercial success as a result; IBM responded by introducing the RISC System/6000 workstations in 1990, which used a new IBM-proprietary RISC processor, the POWER1. All RT PC models were discontinued by May 1991.

The primary operating system for the RT was AIX version 2. Much of the AIX v2 kernel was written in a variant of the PL/I programming language the PL/8, which proved troublesome during the migration to AIX v3. AIX v2 included full TCP/IP networking support, as well as SNA, and two networking file systems: NFS, licensed from Sun Microsystems, and IBM Distributed Services (DS). DS had the distinction of being built on top of SNA, and thereby being fully compatible with DS on the IBM midrange AS/400 and mainframe systems. For the graphical user interfaces, AIX v2 came with the X10R3 and later the X10R4 and X11 releases of the X Window System from MIT, together with the Athena widget set. Compilers for C and Fortran programming languages were available.

Some RT PCs were also shipped with the Academic Operating System (AOS), an IBM port of 4.3BSD Unix to the RT PC. It was offered as an alternative to AIX, the usual RT PC operating system, to US universities eligible for an IBM educational discount. AOS added a few extra features to 4.3BSD, notably NFS, and an almost ANSI C-compliant C compiler. A later version of AOS existed that was derived from 4.3BSD-Reno, but it was not widely distributed.

The RT forced an important stepping-stone in the development of the X Window System, when a group at Brown University ported X version 9 to the system. Problems with reading unaligned data on the RT forced an incompatible protocol change, leading to version 10 in late 1985.

IBM PS/2 series

AIX PS/2 (also known as AIX/386) was developed by Locus Computing Corporation under contract to IBM. AIX PS/2, first released in October 1988, ran on IBM PS/2 personal computers with Intel 386 and compatible processors.AIX PS/2 1.3 AIXwindows Desktop

The product was announced in September 1988 with a baseline tag price of $595, although some utilities like uucp were included in a separate Extension package priced at $250. nroff and troff for AIX were also sold separately in a Text Formatting System package priced at $200. The TCP/IP stack for AIX PS/2 retailed for another $300. The X Window package was priced at $195, and featured a graphical environment called the AIXwindows Desktop, based on IXI’s X.desktop. The C and FORTRAN compilers each had a price tag of $275. Locus also made available their DOS Merge virtual machine environment for AIX, which could run MS DOS 3.3 applications inside AIX; DOS Merge was sold separately for another $250. IBM also offered a $150 AIX PS/2 DOS Server Program, which provided file server and print server services for client computers running PC DOS 3.3.

The last version of PS/2 AIX is 1.3. It was released in 1992 and announced to add support for non-IBM (non-microchannel) computers as well. Support for PS/2 AIX ended in March 1995.

AIX version 3 and 4

Among other variants, IBM later produced AIX Version 3 (also known as AIX/6000), based on System V Release 3, for their POWER-based RS/6000 platform. Since 1990, AIX has served as the primary operating system for the RS/6000 series (later renamed IBM eServer pSeries, then IBM System p, and now IBM Power Systems). AIX Version 4, introduced in 1994, added symmetric multiprocessing with the introduction of the first RS/6000 SMP servers and continued to evolve through the 1990s, culminating with AIX 4.3.3 in 1999. Version 4.1, in a slightly modified form, was also the standard operating system for the Apple Network Server systems sold by Apple Computer to complement the Macintosh line.

RISC System/6000 (RS/6000)

The RISC System/6000 (RS/6000), is a family of RISC-based Unix servers, workstations and supercomputers made by IBM in the 1990s. The RS/6000 family replaced the IBM RT PC computer platform in February 1990 and was the first computer line to see the use of IBM’s POWER and PowerPC based microprocessors. In October 2000, the RS/6000 brand was retired for POWER-based servers and replaced by the eServer pSeries. Workstations continued under the RS/6000 brand until 2002, when new POWER-based workstations were released under the IntelliStation POWER brand.

IBM RS6000 AIX File Servers IBM.COM 1998.jpeg
File servers used by IBM for ibm.com in the late 1990’s. These are RS/6000 AIX servers. The author writes: “ibm.com used AFS to share files amongst systems in Schaumburg, IL and Columbus, OH. The R/W master was in Schaumburg, while R/O secondaries were in Schaumburg and Columbus.”

AIX version 5

AIX 5L 5.1, May 4, 2001

AIX 5.1 on POWER4 architecture made a leap forward towards future virtualization on IBM Power

  • 64 bit kernel installed but not enabled by default
  • Ability to run Logical Partitions on POWER4. A logical partition (LPAR) is a subset of a computer’s hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple logical partitions, each hosting a separate instance of an operating system
  • JFS2 file system up to 1 TB file system with 1 TB file size support
  • Reliable Scalable Cluster Technology
  • Linux Compatible program interface
  • Workload Manager GUI and functional upgrades

AIX 5L 5.2, October 18, 2002

AIX 5.2 brought even more enhancements:

  • Dynamic logical partitioning for processors, memory, and I/O o Dynamic Capacity Upgrade on Demand Enhancements to Scalability and Workload Manager
  • Enhancements to Enterprise Storage Management
  • Cluster Systems Management for monitoring and administering multiple machines (both AIX and Linux) from a single point of control
  • Advanced RAS features
  • Additional security features and enhancements
  • Network enhancements including Mobile IPv6, SNMP V3, and upgrade to BIND V9
  • APIs from the latest C language and single UNIX specification standards

AIX 5L 5.3, August 13, 2004

The enhancements which came with AIX 5L 5.3 combined with POWER5 series enabled an advanced Power virtualization platform which is still in use today on Power Systems (in a form of PowerVM)

  • Micro-partitioning support for a single processor being shared by up to 10 logical partitions
  • Virtual SCSI disks that allow partitions to access storage without requiring a physical storage adapter
  • Virtual networking: Virtual Ethernet provides high-speed connections between partitions; Shared Ethernet Adapter provides connectivity between internal and external VLANs.
  • NFS v4

AIX version 6 and newer

AIX 6 was announced in May 2007, and it ran as an open beta from June 2007 until the general availability (GA) of AIX 6.1 on November 9, 2007. Major new features in AIX 6.1 included full role-based access control, workload partitions (which enable application mobility), enhanced security (Addition of AES encryption type for NFS v3 and v4), and Live Partition Mobility on the POWER6 hardware.

AIX 7.1 was announced in April 2010, and an open beta ran until general availability of AIX 7.1 in September 2010. Several new features, including better scalability, enhanced clustering and management capabilities were added. AIX 7.1 includes a new built-in clustering capability called Cluster Aware AIX. AIX is able to organize multiple LPARs through the multipath communications channel to neighboring CPUs, enabling very high-speed communication between processors. This enables multi-terabyte memory address range and page table access to support global petabyte shared memory space for AIX POWER7 clusters so that software developers can program a cluster as if it were a single system, without using message passing (i.e. semaphore-controlled Inter-process Communication). AIX administrators can use this new capability to cluster a pool of AIX nodes. By default, AIX V7.1 pins kernel memory and includes support to allow applications to pin their kernel stack. Pinning kernel memory and the kernel stack for applications with real-time requirements can provide performance improvements by ensuring that the kernel memory and kernel stack for an application is not paged out.

AIX 7.2 was announced in October 2015, and released in December 2015. AIX 7.2 principal feature is the Live Kernel Update capability which allows OS fixes to replace the entire AIX kernel with no impact to applications, by live migrating workloads to a temporary surrogate AIX OS partition while the original OS partition is patched. AIX 7.2 was also restructured to remove obsolete components. The networking component, bos.net.tcp.client was repackaged to allow additional installation flexibility. Unlike AIX 7.1, AIX 7.2 is only supported on systems based on POWER7 or later processors.

AIX 7.3 is due to be released in Q4 of 2021

More about AIX

The default shell was Bourne shell up to AIX version 3 and was changed in AIX version 4.
The default graphical user interface is CDE – Common Desktop Environment.

As part of the Linux Affinity introduced in AIX version 5 and thanks to the AIX Toolbox for Linux Applications a certain set of open source tools kind of a core set of some of the most common tools like development tools and libraries are available in rpm package form like Curl, Samba and PostreSql tools, sed, mutt.

I left a link in the show notes so You can check for yourself if Your favourite tool is included or not.

SMIT – System Management Interface Tool

SMIT – System Management Interface Tool – The initial menu, when running in text mode

SMIT is the System Management Interface Tool for AIX. It allows a user to navigate a menu hierarchy of commands, rather than using the command line. Invocation is typically achieved with the command smit. Experienced system administrators make use of the F6 function key which generates the command line that SMIT will invoke to complete it. SMIT also generates a log of commands that are performed in the smit.script file. The smit.script file automatically records the commands with the command flags and parameters used. The smit.script file can be used as an executable shell script to rerun system configuration tasks. SMIT also creates the smit.log file, which contains additional detailed information that can be used by programmers in extending the SMIT system.

smit and smitty refer to the same program, though smitty invokes the text-based version, while smit will invoke an X Window System based interface if possible; however, if smit determines that X Window System capabilities are not present, it will present the text-based version instead of failing. Determination of X Window System capabilities is typically performed by checking for the existence of the DISPLAY variable.

Object Data Manager (ODM)

Object Data Manager (ODM) is a database of system information integrated into AIX analogous to the registry in Microsoft Windows. A good understanding of the ODM is essential for managing AIX systems.

Data managed in ODM is stored and maintained as objects with associated attributes. Interaction with ODM is possible via application programming interface (API) library for programs, and command-line utilities such us odmshowodmgetodmaddodmchange and odmdelete for shell scripts and users. SMIT and its associated AIX commands can also be used to query and modify information in the ODM.

Example of information stored in the ODM database are:

  • Network configuration
  • Logical volume management configuration
  • Installed software information
  • Information for logical devices or software drivers
  • List of all AIX supported devices
  • Physical hardware devices installed and their configuration
  • Menus, screens and commands that SMIT uses

My experience with AIX

Zero, Null, Nothing. – AIX Community is much smaller in size than for example Linux and it reminds me more of a secret society with a lot of Secrecy. For a newcomer it is pretty much impossible to get any exposure to it or any experience with it and sometimes even harder to find someone who is willing to help you to start your journey with AIX.

People who helped me from the AIX Community and to whom I am grateful for their support

I want to give special thanks to Andrey Klyachkin from power-devops.com who helped me to get up and running with a small AIX server on the cloud in a matter of hours. Andrey has a vast experience in AIX administration and he is a very pleasant person to talk to.

Please check out his website at power-devops.com (link in the show notes) as he most probably be able to answer your questions regarding AIX operating system and using devops tools on it.

AIX Community and Literature

There are some articles on the web about AIX and some great sites too like http://aix4admins.blogspot.com/ You can also go to reddit at /r/aix but I found it to be mostly for people who has already experience with AIX and have all the required access to the tools and utilities required.

I have to say that because of the size of the AIX Community and the slightly reserved nature of most of its members I came across it is not a very easy task for a newcomer to get acquintance with AIX Operating System and be up and running in no time and as easy as it might be with other distributions like Linux.

I was particularly unlucky as I came across a used AIX server on a secondhand website here in Spain two times from two different sellers but both of them went AWOL on me after we have agreed on the price and a local pickup. 🙁

Therefore up until this day I have stayed without owning a physical Power Architecture Server to run AIX 7.1 or 7.2 on my own in my homelab. (( I am not giving up just yet ))

While there are limited amount of literature out there about AIX in a form of books when compared to Linux, AIX well IBM has something up its sleeve which might give them the upper hand.

IBM Redbooks. IBM Redbooks content is designed to help you learn, adopt and deploy solutions. Their offerings include brief documents, books and videos. And best of all — they’re available at no charge.

While IBM Redbooks aren’t meant to replace IBM manuals or the IBM Knowledge Center. Instead, they offer practical technical information that’s not covered in product manuals.

One of the advantages of IBM Redbooks publications is that you can start learning anytime, anywhere. Redbooks are available for immediate download in PDF and EPUB format, and on-demand printing is available for those who want to read a hard copy.

IBM Redbooks cover IBM and Red Hat solutions as well as third-party and open-source technologies. You can learn about OpenShift on IBM Z and Power, open source IT operations management, security features in IBM Z and LinuxONE, cloud object storage, SAP HANA on Power Systems, agile integration, and so much more than just the AIX Operating System.

I linked one in particular regarding AIX 5L which can come handy to start to learn more about AIX and build upon as you progress further later on.

Get Your Hands on IBM AIX

While there are not really *free* ways to get your hands on AIX there are cloud solutions if you have and wish to spend money and try out AIX.

One of the cheapest and best combination would be to sign up for IBM Cloud account upgrade it to a Pay-As-You-Go Tier and use the welcome voucher 200$ (expires in 1 month) to run an AIX virtual machine until your money runs out with Skytap on IBM Cloud (also available on the Azure Marketplace) or Power Systems Virtual Server offering from IBM Cloud.

IBM Cloud accounts comparison

I recommend that you apply Skytap‘s welcome voucher which is valid for 90 days worth of 500$ to run AIX Virtual Machines for another 3 months after the initial IBM voucher of 200$ rans out using the Power Systems Virtual Server offering. (( I can not confirm if this is something You can do ,,applying the 500$ voucher of Skytap after the 1 month 200$ credit rans out from IBM Cloud ))

Both solutions runs your AIX Operating System as a full virtual machine on an IBM Power Server.

Estimated Price with Power Systems Virtual Server on IBM Cloud

Estimated Price for a shared Scale Out (S922) HW running shared 0.25 vcpu (1 physical core equals 4 vcpus on this HW) with 2GB of Ram and 20GB of Tier 3 Storage for Frankfurt 1 DC Region estimates before taxes and/or any discounts at 44.56 Euros per month.

If you plan to use the VM let’s say 5-6 hours in total per week then in a month your cost will be very little as per these estimates ( around 3-5 euros perhaps)

Estimated Price for third party solution from Skytap on IBM Cloud

Skytap on IBM Cloud VM Control Panel

Estimated usage cost in EMEA Region which is applicable for me for 1x Power based VM for 5 hours per week x 4 = 20 hours a month runtime with 2GB Ram and10GB Storage with 1x CPU set to Entitled Capacity of 0.05 capped/can not go over would be charged around:

Skytap Cloud Power RAM: 20hrs x 2GB x $0.065 = $2.60
Skytap Cloud Storage (persistent): 730 hrs x 10GB x $0.00011 = $0.80
Total: $3.40 per month (i guess its before taxes)

This is very affordable if You want to learn about AIX and when You have some limited time to tinker with it and You do not require it to run 24/7 as most of us hobbyst/homelabbers do not.

Both Skytap’s on IBM Cloud offer and IBM’s Own Power Systems Virtual Server are priced similarly but Skytap seems to have more options to modify / interact with Your Virtual Machine ( boot from a supplied iso you upload to your assets and do an upgrade for example)

Physical hardware

Another option is to purchase some older Power architecture hardware from sites like ebay but I tell you they are not cheap. Most of the time they come wiped without any OS Install discs and even tough You can try to contact IBM representative to obtain install discs for your ,,new” server via its model/serial number it is not always easy without having an actual support contract but your mileage may vary on this.

Also as much as I understood some features come either baked in or not ( activated or not) on your hardware from the factory so its always worth checking out what physical and SW entitlements your server is equipped with. I have limited knowledge here as I do not own any Power architecture server myself.

This path can be interested to some how want to learn and explore features of AIX which can only be explored on bare metal Vs a Cloud virtual machine like IBM AIX’s PowerVM (formerly known as Advanced Power Virtualization) which is a form of para virtualization technique. As far as I can see the server has to come with this enabled from the factory and there is 3 separate editions of it (IBM PowerVM Express/Standard/Enterprise) and it is one of the features I would look for and make sure it exists on the server I am ready to purchase.

PowerVM is available on POWER6 and higher servers.

IBM PowerVM Editions
IBM Power 750 8233 e8b 4x CPU 6-Core, 256 GB RAM

Closing Thoughts

With the advent of Cloud infrastructure it has become easier to get experience with technologies previously unavailable or reserved just to a selected few like IBM’s AIX Unix.

You do not have to purchase expensive hardware and worry about electricity cost and noise if You can make a few compromises coming from the nature of Virtual Machines Vs Physical Hardware.

The running costs of a small Unix server with AIX on the cloud is more affordable than it ever was.

However I still believe that it is necessary that companies like IBM gets rid of old habits and opens towards the community of enthusiasts or hobbyist/homelabbers whom are willing to learn and experiment with Operating Systems like AIX or z/OS in their free time for their own benefit and perhaps to others benefit such as their employer without hurting corporate profits or business intentions in the process.

When corporations like IBM turn themselves away from these insignificant customers who can not afford the license fees and support contracts big enterprises do, what they tend to forget that some of these individuals might be the future C-level or mid-level decision makers.

When the day comes from 12 days or 12 years from now and they need to make a professional recommendation to a platform or a product to implement at their workplace they might not choose your product if they do not know it exists or they have never had any experience with it.

One thing I know for sure is for me to professionally recommend something it has to fit into the below requirements:

  • to know and be familiar with the tool or solution
  • to have a good experience with the brand or corporation who’s offering it
  • to know that it exists (tool , solution , operating system, etc.)
  • to be fit for the requirements

While solution X might tick off 1 out of 4 requirements on my list it is certainly not enough.Not even close.

Let alone if I am not even familiar with it or never had the chance to be exposed to that technology or solution. Now imagine if I even had a bad customer experience with it.

Hobbyst, Homelabbers are no way considered free-riders or someone who eats away corporate profits in my understanding. They are willing to take the thier time for free to use and familiarize themselves with a product or solution of company X. not just for their benefit but perhaps one day for a corporation’s or client’s benefit in the not so distant future. They might or might not be the next C-level decision makers but perhaps the one’s the C-level executive turns to for their opinion and knowledge after a sales representative made its pitch at them.

And seriously what damage a guy with a 42U rack and some used hardware can do from his basement running anything no matter how mission critical that piece of software is being it z/OS or AIX or OpenVMS or HP-UX?

Rule of thumb:

Treat me like I was the C-level executive You wish to present your sales pitch tomorrow.

Viktor Madarasz


Andrey Klyachkin’s power-devops.com website

AIX for System Administrators
Practical Guide to AIX (and PowerVM, PowerHA, PowerVC, HMC, DevOps …)

HT-1080Z School Computer

Video Genie

IBM AIX PS/2 1.3 for Intel i386 in Virtual Box

Skytap 500$ welcome voucher valid for 90 days for new IBM Cloud users

IBM Power and AIX

IBM Redbooks – Example AIX 5L

AIX 5L release notes



AIX Toolbox for Liux Applications

Open Software Foundation

AIX & Qemu ( for the ones who would like to have some fun )
( in my opinion somewhat working and slow performance compared to the VM offerings in the cloud I have explored but nevertheless can be a fun experiment or spend time activity)

Andrey Klyachkin – Install AIX 7.2 in Qemu