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1: <HTML> 2: <HEAD> 3: <TITLE>Microcomputer OS History</TITLE> 4: </HEAD> 5: <BODY BACKGROUND="../images/linen2d.jpg"> 6:  7: <TABLE CELLPADDING=3 BORDER=0 WIDTH=100%> 8: <TR> 9: <TD WIDTH=25% VALIGN=TOP> 10:  11: </TD> 12: <TD WIDTH=75% VALIGN=TOP> 13: <H1>Microcomputer OS History</H1> 14: 15: <H2>Timeline</H2> 16: 17: 18: <A HREF="images/os_history.png" TARGET="about:blank"><IMG SRC="images/os_history.png" WIDTH="100%"></A> 19: <A HREF="images/os_history.png" TARGET="about:blank">See full-size version</A> (Opens in new window) 20: 21: 22: 23: <H2>CP/M (Control Program/Monitor)</H2> 24: 25: CP/M was developed by the late Gary Kildall of Digital Research Inc., originally Intergalactic Digital Research. 26: As the first de facto standard among microcomputer operating systems, CP/M ran on a very wide variety of 27: competing hardware platforms. Although many of CP/M's supported platforms were vastly different in architecture, 28: power, and peripherals (meaning that binary programs could not be shared among different types of CP/M machines), 29: application programs could be easily ported, if they limited themselves to the API supplied by the operating system, 30: rather than accessing hardware directly. In fact, DRI often provided source translator automata for converting assembly 31: language programs from one supported platform to the other. 32: 33: Architecturally, CP/M was divided into three parts. These were the Basic Input/Output System or BIOS, 34: the Basic Disk Operating System or BDOS, and the Console Command Processor or CCP. 35: This is where we get the term "BIOS", as applied to the ROM-based firmware of the IBM-compatible x86 family of microcomputers, still in wide use today <SUPER><A HREF="#footnote1">1</A></SUPER>. 36: 37: The BIOS was the only hardware-dependent component of CP/M, and can be considered as a primitive hardware abstraction layer, or HAL. 38: BDOS restricted itself to calling the BIOS. Portability was enhanced by the fact that at least the BDOS and CCP were written 39: in PL/M (Programming Language for Microcomputers), a high-level language conceived by Kildall in 1973 with similarities to 40: PL/I and ALGOL. 41: 42: CP/M rapidly lost ground to PC-DOS and MS-DOS after the introduction of the IBM Personal Computer in 1981. However, 43: CP/M-86 was eventually released on the IBM PC, a product which gained little traction against Microsoft's dominance. The CP/M 44: family of operating systems eventually came to include MP/M (a multiuser version of CP/M), and Concurrent CP/M, a multitasking 45: version of CP/M that was ultimately developed into Concurrent DOS, which was a multitasking MS-DOS clone that itself became 46: DR-DOS, which enjoyed a mild degree of success among x86 power users, and was well-reviewed by the computer press of the time. 47: 48: DR-DOS was eventually sold to Novell, becoming Novell DOS. Novell sold most of its non-NetWare OS properties to Caldera in the 49: late 1990s, and Novell DOS became Caldera OpenDOS. 50: 51: CP/M still enjoys wide use among retrocomputing hobbyists. 52: 53: <H2>MS-DOS</H2> 54: 55: MS-DOS was originally developed in 1980 as QDOS (the Quick and Dirty OS) by Tim Paterson of Seattle Computer Products, 56: as an 8086-based clone of Digital Research CP/M. It improved upon CP/M in several ways: where CP/M's disk cache logic required the 57: machine to be rebooted if a new disk was inserted into the floppy drive, QDOS did not. Also, QDOS implemented the FAT12 filesystem 58: used by Microsoft's Disk BASIC instead of the CP/M filesystem, and also had more intuitive commands (such as COPY instead of PIP). 59: 60: QDOS was sold with SCP's 8086 computer kits, and was eventually renamed 86-DOS. Microsoft purchased 86-DOS from SCP 61: and ported it to the original IBM PC in 1981, renaming it MS-DOS. IBM was granted a non-exclusive license to supply MS-DOS (as IBM PC-DOS) 62: for its own machines. 63: 64: IBM PC-DOS continued as a distinct IBM product until the late 1990s release of PC-DOS 2000. 65: 66: MS-DOS 2.0 introduced UNIX-style pipelines, installable device drivers, and hierarchical directory support in the FAT filesystem. It also 67: added support for accessing files through file handles rather than the clumsier CP/M approach of FCBs, or File Control Blocks. 68: 69: MS-DOS 5.0 was a full re-write of the operating system, largely performed by Microsoft star programmer Charles Simonyi, the original 70: implementer of Microsoft Word and Excel. 71: 72: MS-DOS, unlike CP/M, was written in hand-tuned 8086 assembly language. It runs in 8086 real mode, although the advent of 80286 (and higher) 73: CPUs added support for memory above 1MB. Very large programs could eventually use EMS memory. EMS is a standard developed by Lotus Development Corp., 74: Intel, and Microsoft (the LIM Expanded Memory Specification) for access of bank-switched memory mapped into free areas of the UMA, which was memory 75: between 640KB and 1MB. 76: 77: EMS memory was originally supplied via expansion boards, but expanded memory support was later supplied most often by a software package (such as 78: Microsoft's EMM386, Qualitas 386MAX, and Quarterdeck QEMM) which used XMS memory to simulate EMS memory. XMS memory (eXtended Memory Specification) 79: support was provided by HIMEM.SYS in MS-DOS 5.0 and later, and in earlier operating systems (or in the case of users who chose a third-party memory 80: manager), by equivalent drivers provided by the above memory management products. 81: 82: Many MS-DOS programs implemented later in the operating system's lifetime actually ran in 386 protected mode, using what is 83: called a "DOS Extender", which is a program often conforming to the DPMI (or DOS Protected Mode Interface) specification, using the 84: 80386 Virtual 8086 mode to allow DOS programs running in protected mode to make calls to DOS and BIOS APIs. 85: 86: It can be argued that early versions of Microsoft Windows were themselves a type of DOS extender. The degree to which any given 87: non-NT-kernel-based version of Windows can be considered a DOS extender or a standalone operating system is a highly complex and nuanced discussion, 88: involving various modes of operation in which Windows can be run, as well as the engagement of various, optional Windows components. 89: 90: <H2>Microsoft Windows (non-NT)</H2> 91: 92: Microsoft Windows 1.01 was released in 1985. It was a task-switching graphical shell for MS-DOS, that provided an API and an SDK 93: for GUI application development. It used a GUI file manager application called the MS-DOS Executive to manage and launch 94: programs and files. It ran only in 8086 real mode, and could thus only access the first 640KB of memory on the host. The XT-class microcomputers 95: common in its day had barely enough power to run Windows, which limited its popularity. Windows 1.01 did not support overlapping windows on the 96: screen, and used the terms iconify and zoom, instead of the now-familiar minimize and maximize. 97: 98: Windows 1.01 strictly relied upon DOS and BIOS APIs to access the hardware of the computer. 99: 100: Windows 2.0 introduced overlapping windows, prompting a lawsuit from Apple Computer, which claimed to own the technology for overlapping windows. 101: Architecturally, Windows 2.x eventually added 80286- and 80386-specific versions (Windows/286 and Windows/386), which began to blur the distinction 102: between graphical shell and operating system, providing native Windows drivers for increasingly more hardware. 103: 104: Windows 3.0 was the first truly successful release of Windows, replacing the MS-DOS Executive with Program Manager and 105: File Manager. It ran in Real Mode (corresponding to the 8086 real address mode), Standard Mode 106: (corresponding to 80286 protected mode), and 386 Enhanced Mode (corresponding to 80386 protected mode). Individual applications 107: in any of these modes were cooperatively multitasked, but still themselves 16-bit applications. DOS and BIOS were still used to access the filesystem 108: and much of the hardware. MS-DOS applications could be run under Windows in standard mode or 386 Enhanced mode, but in any mode other than 386 Enhanced 109: mode, only one MS-DOS application could be run at a time, and then only in full screen. 386 Enhanced mode allowed multiple MS-DOS applications to 110: run, each in its own window. 111: 112: Windows 3.1 eliminated Real Mode and improved stability, as well as adding multimedia device support (previously limited to the Microsoft Multimedia 113: Extensions, a set of extensions for Windows 3.0 only available to hardware OEMs) to Windows itself. 114: 115: Windows for Workgroups eliminated standard mode, and provided optional 32-bit disk access and 32-bit file access. When these two components were enabled, 116: Windows for Workgroups could be considered to be nearly a full, standalone operating system, with DOS being used only as a boot loader, as DOS and BIOS 117: APIs were no longer needed for access to media. Windows for Workgroups also added networking support, and the Win32s extensions allowed a small subset 118: of 32-bit applications designed for a subset of the Windows NT API to run. 119: 120: Windows 95, released on August 24, 1995, added 32-bit application support, support for 255-character filenames, an improved GUI, preemptive multitasking, 121: and multithreading. It implemented a subset of the Windows NT API (excluding Unicode and security APIs), and retained full support for MS-DOS applications. 122: Windows 95 no longer had to be started via WIN.COM from an MS-DOS prompt, but instead loaded directly on machine boot-up. CONFIG.SYS and AUTOEXEC.BAT could 123: be eliminated, provided the computer required no real-mode device drivers to support its hardware. It instantiated an MS-DOS virtual machine using Virtual-8086 mode 124: on bootup, and if provided, CONFIG.SYS and AUTOEXEC.BAT would provide the base environment for any MS-DOS application being run, with each MS-DOS application 125: inheriting the base VM's environment and configuration. 126: 127: Note that LFN support in Win95 was still FAT16-based, but used reserved header areas to support this, through a system called VFAT. The 128: MS-DOS interrupt 21h APIs for handling file access through file handles were also enhanced to add LFN support, used in at least the MS-DOS Editor and the supplied 129: DOS utilities. The File Control Block (FCB) APIs were not, however, given the same enhancement. There was discussion at Microsoft of releasing MS-DOS 7.0 130: as a standalone product, but these plans were eventually scrapped. 131: 132: Windows 9x can be considered an extension to the Windows for Workgroups 3.11 386 Enhanced Mode kernel. For a discussion of the Windows 95 architecture, 133: see <A HREF="https://youngmumpster.wordpress.com/2013/10/13/windows-multitasking-a-historical-aside/">Windows Multitasking: A Historical Aside</A> on my tech blog. 134: 135: Windows 98 and Windows Millennium Edition continued to extend this platform until around 1999 or 2000, adding support for things like USB, FAT32, and dual-head monitor configurations. 136: 137: <H2>OS/2 (Operating System/2)</H2> 138: 139: The result of a Joint Development Agreement between Microsoft and IBM, OS/2 was designed alongside the IBM PS/2 line of microcomputers, and 140: was intended to provide a modern replacement for MS-DOS and PC-DOS, breaking the 640KB memory barrier of the latter operating systems. 141: 142: OS/2 was originally implemented as a multitasking, 16-bit, 80286 protected mode operating system. The original 1987 release did not have a graphical 143: user interface, but OS/2 1.1 added a Windows 2.x-style GUI, called Presentation Manager. The Presentation Manager API was at least superficially 144: similar to the Microsoft Windows API, but with somewhat more consistent API names, and the Presentation Manager coordinate system used a different 145: point of origin, i.e., the location of (0, 0) was different. 146: 147: OS/2 1.3 changed the Presentation Manager UI to match Windows 3.0. 148: 149: Following the release of Microsoft Windows 3.0, Microsoft abandoned its joint development agreement with IBM in order to focus on its Windows 150: product line exclusively. 151: 152: OS/2 2.0, developed solely by IBM's Personal Systems Products division, added support for 80386 protected mode, and many parts of the operating 153: system were extended from 16-bit to 32-bit. OS/2 2.0 also added the Workplace Shell, an advanced, object-oriented GUI built around IBM's CUA (or 154: Common User Access) standards, and implemented using IBM's System Object Model (or SOM) ABI and API. SOM is conceptually similar to Microsoft's 155: Component Object Model (COM, not to be confused with .COM executables in MS-DOS and CP/M), and Netscape/Mozilla's XPCOM. 156: 157: OS/2 2.1 furthered the extension of OS/2 from a 16-bit to a 32-bit operating system. OS/2 could run 16-bit Windows applications, either in a 158: shared virtual machine, or in dedicated, protected virtual machines. It could also run MS-DOS applications, providing far better compatibility for 159: said applications than any Windows version ever could, including games. 160: 161: OS/2 Warp v3 reduced hardware requirements, improved the installation experience, added multimedia device support, added the LaunchPad application launcher, and introduced the 162: BonusPak, which contained a suite of productivity applications such as a word processor and a spreadsheet, multimedia applications for video production 163: and image management, as well as a dialup-only TCP/IP stack, including support for telnet, FTP, Gopher, e-mail, and USENET newsgroups. A web browser, 164: known as IBM WebExplorer, was added as an optional download later. Dialers were included for IBM's own ISP, as well as a SLIP-only dialer for users 165: wishing to connect to a non-IBM ISP. The BonusPak also included an OS/2 port of the CompuServe Information Manager. OS/2 Warp v3 sold very well 166: until Windows 95 was released, and was the high point of OS/2's success. 167: 168: OS/2 Warp Connect v3 added support for TCP/IP over non-dialup connections, including Ethernet, ATM, Token Ring, and others, bundling IBM's 169: Multi-Protocol Transport Services (MPTS), IBM Peer (for SMB-based networking), and IBM LAN Server domain support into the base product. 170: 171: IBM PSP invested billions of dollars attempting to port OS/2 to the PowerPC platform, in an attempt to disrupt the Intel/Microsoft desktop 172: hegemony, as part of the AIM (Apple, IBM, Motorola) Alliance, a collaboration which also produced the PReP (PowerPC Reference Platform). The 173: failure of this project contributed greatly to the dissolution of the IBM Personal Systems Products division, as CEO Lou Gerstner began to 174: eviscerate IBM's less-profitable divisions, conceding the desktop OS war to Microsoft. 175: 176: OS/2 Warp v4 was the last version of OS/2 to be commercially sold by IBM. It revamped the UI, added a new application launcher that followed 177: the Windows "Start" menu metaphor, enhanced the online help facility, and added voice command support (VoiceType) to the base product, allowing a user to 178: open programs and perform other operations by speaking commands into a microphone. 179: 180: OS/2 Warp v4 was followed on by OS/2 Warp 4.51 and OS/2 Warp 4.52, known as the MCPs, or "Merlin Convenience Packs". These substantial updates 181: were only available to IBM's commercial customers, or those with a Software Subscription. 182: 183: OS/2 became the basis for IBM's ill-fated WorkSpace On-Demand (WSOD) product, and ceased commercial availability in 2006. A third-party 184: company called Serenity Systems eventually acquired a license from IBM to sell a modernized and enhanced OS/2-based operating system under the name 185: "eComStation", which produced roughly three major releases, before entering an uncertain ownership and development status. It is widely assumed that 186: eComStation is now a dead product, and a company called Arca Noae now produces a similarly-licensed OS/2-based operating system called "ArcaOS", which 187: is still supported, and under continuous development and enhancement. 188: 189: The OS/2 community is still quite dedicated, and manages to produce annual conferences in the US and Europe, called WarpStock. Several OS/2 User Groups 190: still exist, and many ports of free and open-source software--generally requiring OS/2 Warp v4 or newer--have given the operating system new life, in 191: spite of IBM's wholesale withdrawal of sales and support. 192: 193: In 2005, IBM withdrew from the PC market it had created, selling off its then-current line of x86 personal computers to Chinese electronics manufacturer 194: Lenovo. 195: 196: 197: <H2>Windows NT</H2> 198: 199: Windows NT (where "NT" originally stood for "New Technology") was introduced as Windows NT 3.1 on July 27, 1993. It used a brand-new, 200: fully 32-bit, protected-mode, preemptive multitasking microkernel developed by Dave Cutler, the original engineer for Digital Equipment Corporation's VMS 201: operating system, an OS from which Windows NT derives many of its architectural features. 202: 203: Originally developed as "NT OS/2" for "New Technology OS/2", the "OS/2" label was dropped when Microsoft abandoned the IBM/Microsoft Joint Development 204: Agreement for OS/2, instead choosing to put all of its efforts behind its own Windows product. 205: 206: While Windows 1.01 through Windows Me were written in highly platform-specific assembly language and C code, the majority of Windows NT, outside 207: of its Hardware Abstraction Layer, is written in portable C++ code. It was conceived with portability, security, and stability as its major design goals. 208: 209: Windows NT (and all Windows versions derived from it) have much more demanding hardware requirements, and implement NTFS as their native filesystem. NTFS 210: provides support for compound files consisting of multiple data streams, advanced permissions, access control lists, long filenames, and less susceptibility to 211: fragmentation. 212: 213: Windows NT provides multiple APIs atop its microkernel. They are: 214: 215: <UL> 216: <LI>Win32 - the native Windows API</LI> 217: <LI>POSIX</LI> 218: <LI>OS/2 - providing support for non-graphical, 16-bit OS/2 1.x programs</LI> 219: </UL> 220: 221: 222: 223: One could argue that Win16 and DOS application support in Windows NT, supplied by the Windows-on-Windows and NTVDM subsystems, could be counted as 224: other APIs, but Microsoft documentation generally counts these two subsystems as backwards compatibility mechanisms, rather than first-class API 225: "personalities". 226: 227: Windows NT has, over the course of its lifetime, been ported to 80386, x86-64, Itanium, MIPS, Alpha, PowerPC, and ARM processors, and eventually 228: replaced the non-NT-based Windows operating systems when the product lines were merged in the release of Windows XP. 229: 230: 231: <HR> 232: <UL> 233: <LI><A NAME="footnote1"></A><SUPER>1</SUPER> ROM BIOS on IBM PC compatibles has largely been supplanted by the Unified Extensible Firmware Interface.</LI> 234: </UL> 235: </TD> 236: </TR> 237: </TABLE> 238: Revision History 239: <PRE> 240: $Log: index.shtml,v $ 241: Revision 1.1 2025/02/20 01:30:51 snw 242: initial commit 243: 244: Revision 1.7 2019/09/03 15:51:40 jpw 245: Remove redundant horizontal rule 246: 247: Revision 1.6 2019/09/03 15:48:44 jpw 248: Fix sidebar include 249: 250: Revision 1.5 2019/09/03 15:48:28 jpw 251: Add sidebar 252: 253: Revision 1.4 2018/12/17 15:50:19 jpw 254: Fix some wording, add references to OS/2 Warp 4.51 and 4.52 255: 256: Revision 1.3 2018/12/15 18:03:23 jpw 257: Add reference to Windows Multitasking article on YOUNGMUMPSTER. 258: 259: Revision 1.2 2018/12/15 17:58:14 jpw 260: Apply some fixes from DrScriptt 261: 262: Revision 1.1 2018/12/14 17:38:40 jpw 263: Initial revision 264: 265: </PRE> 266: Thanks to DrScriptt for his invaluable feedback in the production of this article. 267: <HR> 268: <CENTER> 269: Copyright © 2025 Serena Willis 270: Last modified $Date: 2025/02/20 01:30:51 $ 271: 272: $Id: index.shtml,v 1.1 2025/02/20 01:30:51 snw Exp $ 273: 274: <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-nc-nd/4.0/88x31.png" /></a> This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License</a>. 275: 276: </CENTER> 277: 278: </BODY>