Interactive Systems Corporation
Interactive Systems Corporation was a US-based software company and the first vendor of the Unix operating system outside AT&T, operating from Santa Monica, California. It was founded in 1977 by Peter G. Weiner, a RAND Corporation researcher who had founded the Yale University computer science department and had been the Ph. D. advisor to Brian Kernighan, one of Unix's developers at AT&T. Weiner was joined by Heinz Lycklama a veteran of AT&T and the author of a Version 6 Unix port to the LSI-11 computer. ISC was acquired by the Eastman Kodak Company in 1988, which sold its ISC Unix operating system assets to Sun Microsystems on September 26, 1991. Kodak sold the remaining parts of ISC to SHL Systemhouse Inc in 1993. Several former ISC staff founded Segue Software which partnered with Lotus Development to develop the Unix version of Lotus 1-2-3 and with Peter Norton Computing to develop the Unix version of the Norton Utilities. ISC's 1977 offering, IS/1, was a Version 6 Unix variant enhanced for office automation running on the PDP-11.
IS/3 and IS/5 were enhanced versions of Unix System III and System V for PDP-11 and VAX. ISC Unix ports to the IBM PC included a variant of System III, developed under contract to IBM, known as PC/IX, with versions branded 386/ix and INTERACTIVE UNIX System V/386. ISC was AT&T's "Principal Publisher" for System V.4 on the Intel platform. ISC was involved in the development of VM/IX and enhancements to IX/370, they developed the AIX 1.0 for the IBM RT PC, again under contract to IBM, although IBM awarded the development contract for AIX version 2 of AIX/386 and AIX/370 to the competing Locus Computing Corporation. Although observers in the early 1980s expected that IBM would choose Microsoft Xenix or a version from AT&T Corporation as the Unix for its microcomputer, PC/IX was the first Unix implementation for the IBM PC XT available directly from IBM. According to Bob Blake, the PC/IX product manager for IBM, their "primary objective was to make a credible Unix system - not try to'IBM-ize' the product.
PC-IX is System III Unix." PC/IX was not however the first Unix port to the XT. Venix/86 preceded PC/IX by about a year; the main addition to PC/IX was the INed screen editor from ISC. INed offered multiple windows and context-sensitive help, paragraph justification and margin changes, although it was not a fledged word processor. PC/IX omitted the System III FORTRAN compiler, the tar file archiver and did not add BSD tools like vi or the C shell. One reason for not porting these was that in PC/IX individual applications were limited to a single segment of 64 KB of RAM. To achieve good filesystem performance, PC/IX directly addressed the XT hard-drive rather than doing this through the BIOS, which gave it a significant speed advantage compared to MS-DOS; because of the lack of true memory protection in the 8088 chips, IBM only sold single-user licenses for PC/IX. The PC/IX distribution was accompanied by a 1,800-page manual. Installed, PC/IX took 4.5 MB of disk space. An editorial by Bill Machrone in PC Magazine at the time of PC/IX's launch flagged the $900 price as a show stopper given its lack of compatibility with MS-DOS applications.
PC/IX was not a commercial success although BYTE in August 1984 described it as "a complete, usable single-user implementation that does what can be done with the 8088", noting that PC/IX on the PC outperformed Venix on the PDP-11/23. PC/IX was succeeded by 386/ix in a System VR3 derivative. Versions were termed INTERACTIVE UNIX System V/386 and based on System V 3.2, though with elements of BSD added. Its SVR3.2 kernel meant diminished compatibility with other Unix ports in the early nineties, but the INTERACTIVE UNIX System was praised by a PC Magazine reviewer for its stability. After its acquisition of Interactive, Sun Microsystems continued to maintain INTERACTIVE UNIX System, offering it as a low-end alternative to its System V.4-based Solaris when the latter had been ported to x86-based desktop machines. The last version was "System V/386 Release 3.2 Version 4.1.1", released in July 1998. Official support ended on July 2006, five years after Sun withdrew the product from sale; until version ISA 3.0.1, INTERACTIVE UNIX System supported only 16 MB of RAM.
In the next versions, it supported 256 MB PCI bus. EISA versions always supported 256MB RAM. Coherent William B. Twitty. UNIX on the IBM PC. Prentice-Hall. ISBN 978-0-13-939075-3. Covers and compares PC/IX, Venix. Maurice J. Bach, The Design of the UNIX Operating System, ISBN 0-13-201799-7, Prentice Hall, 1986. IBM has snubbed both Microsoft's multimillion dollar investment in Xenix and AT&T's determination to establish System V as the dominant version on Unix. IBM's latest hot potato Interactive Unix Documentation
IBM Personal Computer XT
The IBM Personal Computer XT shortened to the IBM XT, PC XT, or XT, is a version of the IBM PC with a built-in hard drive. It was released as IBM Machine Type number 5160 on March 8, 1983. Apart from the hard drive, it was the same as the original PC, with only minor improvements; the XT was intended as an enhanced IBM PC for business users. Floppy-only models would replace the original model 5150 PC. A corresponding 3270 PC featuring 3270 terminal emulation was released in October 1983. XT stands for eXtended Technology; the IBM Personal Computer XT came with 128 KB of RAM, a 360 KB double-sided 5¼ inch floppy disk drive, a 10 MB Seagate ST-412 hard drive with Xebec 1210 Modified Frequency Modulation controller, an Asynchronous Adapter, a 130-watt power supply. The motherboard had an Intel 8088 microprocessor running at 4.77 MHz, with a socket for an optional 8087 math coprocessor. IBM recognized soon after the IBM PC's release in 1981 that its five 8-bit "I/O channel" expansion slots were insufficient.
An internal IBM publication stated in October 1981 about the number that "In my opinion, it could be a problem", reporting that others within IBM advised swapping cards if necessary. Every PC required at least a display adapter card and a floppy disk controller card, leaving only three slots available for a parallel printer port card, a serial port card, memory expansion boards, a 3rd-party hard disk controller card, a second display adapter card, or possible other special adapter cards; when IBM announced a successor product to the PC in early 1983, initial speculations were that it would be a next-generation machine based on the Intel 8086 or include other advanced features. When the XT was unveiled however, there was mild disappointment that the new machine was an incremental improvement of the PC based on the same 8088 CPU and would in fact not replace it at all. A BYTE Magazine article commented that "DOS 2.0 is more revolutionary and advanced than the computer itself." A Seagate ST-412 hard disk was standard equipment, the XT was not offered in a floppy-only model for its first two years on the market, although the standard ribbon cable with two floppy connectors was still included.
The only way to purchase an XT with factory-installed dual floppy drives was if the user bought the optional 5161 expansion chassis and placed the hard disk in that, which in effect amounted to purchasing two hard disks as the 5161 came with one standard. Unlike many hard disk systems on microcomputers at the time, the XT was able to boot directly off the drive and did not require a boot floppy. Aside from the hard disk, a serial port card was standard equipment on the XT, all other cards being optional. By the end of 1983, the XT was neck-and-neck with the original PC for sales and IBM were selling every one that they made; the XT had eight slots. Two were behind the floppy drive, shorter than the original PC's slots; the other six fit into the same space as the original PC's five slots. Most PC cards would not fit into the two short slots, some would not fit into the six standard-length, but narrower, slots cards with double boards on them; the floppy and hard drive adapters, the serial port card, nearly always a display adapter board occupied slots.
The basic specification was soon upgraded to have 256 KB of RAM as standard. Expansion slots could be used for memory expansion. Available Video cards were the Monochrome Display Adapter and Color Graphics Adapter, with Enhanced Graphics Adapter and Professional Graphics Controller becoming available in 1984; the XT had a desktop case similar to that of the IBM PC. It weighed 32 pounds and was 19.5 inches wide by 16 inches deep by 5.5 inches high. The power supply of the original XT sold in the US was configured for 120 V AC only and could not be used with 240 V mains supplies. XTs with 240 V-compatible power supplies were sold in international markets. Both were rated at 130 watts; the operating system sold with the XT was PC DOS 2.0 or, by the time the XT was discontinued in early 1987, DOS 3.2. Like the original PC, the XT came with IBM BASIC in its ROM. Despite the lack of a cassette port on XTs, IBM's licensing agreement with Microsoft forced them to include BASIC on all their PCs, the BASICA program, included with DOS depended on the BASIC ROM.
The XT BIOS displayed a memory count during the POST, unlike the PC. The XT was discontinued in the spring of 1987, replaced by the PS/2 Model 30. XT motherboards came in two different versions; the original had 64 KB of 4164 RAM socketed on it with further sockets to support up to 256 KB and any more RAM had to be put on an expansion card, of which the AST Research Six Pak was the most widespread and popular. XTs produced in 1983-84 shipped in 1985, 256k; the second version had 256 KB socketed on it and could accommodate the entire 640 KB. XTs used 4164 DRAMs only for the first 256k and the remainder of system memory consisted of larger 41256 DRAMs; as a result, it took only 44 RAM chips to reach 640 kB versus the 80 chips needed on the original model XT. There were two or three revisions of the motherboard with minor differences between them; the first version incorporates a 470 ohm resistor to fix a race condition between the CPU and DMA controller which created the possibility of the system locking up.
In the spring o
BIOS is non-volatile firmware used to perform hardware initialization during the booting process, to provide runtime services for operating systems and programs. The BIOS firmware comes pre-installed on a personal computer's system board, it is the first software to run when powered on; the name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS proprietary to the IBM PC has been reverse engineered by companies looking to create compatible systems; the interface of that original system serves as a de facto standard. The BIOS in modern PCs initializes and tests the system hardware components, loads a boot loader from a mass memory device which initializes an operating system. In the era of DOS, the BIOS provided a hardware abstraction layer for the keyboard and other input/output devices that standardized an interface to application programs and the operating system. More recent operating systems do not use the BIOS after loading, instead accessing the hardware components directly.
Most BIOS implementations are designed to work with a particular computer or motherboard model, by interfacing with various devices that make up the complementary system chipset. BIOS firmware was stored in a ROM chip on the PC motherboard. In modern computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard; this allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it creates a possibility for the computer to become infected with BIOS rootkits. Furthermore, a BIOS upgrade that fails can brick the motherboard permanently, unless the system includes some form of backup for this case. Unified Extensible Firmware Interface is a successor to the legacy PC BIOS, aiming to address its technical shortcomings; the term BIOS was created by Gary Kildall and first appeared in the CP/M operating system in 1975, describing the machine-specific part of CP/M loaded during boot time that interfaces directly with the hardware.
Versions of MS-DOS, PC DOS or DR-DOS contain a file called variously "IO. SYS", "IBMBIO. COM", "IBMBIO. SYS", or "DRBIOS. SYS". Together with the underlying hardware-specific but operating system-independent "System BIOS", which resides in ROM, it represents the analogue to the "CP/M BIOS". With the introduction of PS/2 machines, IBM divided the System BIOS into real- and protected-mode portions; the real-mode portion was meant to provide backward compatibility with existing operating systems such as DOS, therefore was named "CBIOS", whereas the "ABIOS" provided new interfaces suited for multitasking operating systems such as OS/2. The BIOS of the original IBM PC and XT had no interactive user interface. Error codes or messages were displayed on the screen, or coded series of sounds were generated to signal errors when the power-on self-test had not proceeded to the point of initializing a video display adapter. Options on the IBM PC and XT were set by switches and jumpers on the main board and on expansion cards.
Starting around the mid-1990s, it became typical for the BIOS ROM to include a "BIOS configuration utility" or "BIOS setup utility", accessed at system power-up by a particular key sequence. This program allowed the user to set system configuration options, of the type set using DIP switches, through an interactive menu system controlled through the keyboard. In the interim period, IBM-compatible PCs—including the IBM AT—held configuration settings in battery-backed RAM and used a bootable configuration program on disk, not in the ROM, to set the configuration options contained in this memory; the disk was supplied with the computer, if it was lost the system settings could not be changed. The same applied in general to computers with an EISA bus, for which the configuration program was called an EISA Configuration Utility. A modern Wintel-compatible computer provides a setup routine unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; when errors occur at boot time, a modern BIOS displays user-friendly error messages presented as pop-up boxes in a TUI style, offers to enter the BIOS setup utility or to ignore the error and proceed if possible.
Instead of battery-backed RAM, the modern Wintel machine may store the BIOS configuration settings in flash ROM the same flash ROM that holds the BIOS itself. Early Intel processors started at physical address 000FFFF0h. Systems with processors provide logic to start running the BIOS from the system ROM. If the system has just been powered up or the reset button was pressed, the full power-on self-test is run. If Ctrl+Alt+Delete was pressed, a special flag value stored in nonvolatile BIOS memory tested by the BIOS allows bypass of the lengthy POST and memory detection; the POST identifies, initializes system devices such as the CPU, RAM, interrupt and DMA controllers and other parts of the chipset, video display card, hard disk drive, optical disc drive and other basic hardware. Early IBM PCs had a routine in the POST that would download a program into RAM through the keyboard port and run it; this featur
The user interface, in the industrial design field of human–computer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, process controls; the design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology. The goal of user interface design is to produce a user interface which makes it easy and enjoyable to operate a machine in the way which produces the desired result; this means that the operator needs to provide minimal input to achieve the desired output, that the machine minimizes undesired outputs to the human. User interfaces are composed of one or more layers including a human-machine interface interfaces machines with physical input hardware such a keyboards, game pads and output hardware such as computer monitors and printers.
A device that implements a HMI is called a human interface device. Other terms for human-machine interfaces are man–machine interface and when the machine in question is a computer human–computer interface. Additional UI layers may interact with one or more human sense, including: tactile UI, visual UI, auditory UI, olfactory UI, equilibrial UI, gustatory UI. Composite user interfaces are UIs that interact with two or more senses; the most common CUI is a graphical user interface, composed of a tactile UI and a visual UI capable of displaying graphics. When sound is added to a GUI it becomes a multimedia user interface. There are three broad categories of CUI: standard and augmented. Standard composite user interfaces use standard human interface devices like keyboards and computer monitors; when the CUI blocks out the real world to create a virtual reality, the CUI is virtual and uses a virtual reality interface. When the CUI does not block out the real world and creates augmented reality, the CUI is augmented and uses an augmented reality interface.
When a UI interacts with all human senses, it is called a qualia interface, named after the theory of qualia. CUI may be classified by how many senses they interact with as either an X-sense virtual reality interface or X-sense augmented reality interface, where X is the number of senses interfaced with. For example, a Smell-O-Vision is a 3-sense Standard CUI with visual display and smells; the user interface or human–machine interface is the part of the machine that handles the human–machine interaction. Membrane switches, rubber keypads and touchscreens are examples of the physical part of the Human Machine Interface which we can see and touch. In complex systems, the human–machine interface is computerized; the term human–computer interface refers to this kind of system. In the context of computing, the term extends as well to the software dedicated to control the physical elements used for human-computer interaction; the engineering of the human–machine interfaces is enhanced by considering ergonomics.
The corresponding disciplines are human factors engineering and usability engineering, part of systems engineering. Tools used for incorporating human factors in the interface design are developed based on knowledge of computer science, such as computer graphics, operating systems, programming languages. Nowadays, we use the expression graphical user interface for human–machine interface on computers, as nearly all of them are now using graphics. There is a difference between a user interface and an operator interface or a human–machine interface; the term "user interface" is used in the context of computer systems and electronic devices Where a network of equipment or computers are interlinked through an MES -or Host to display information. A human-machine interface is local to one machine or piece of equipment, is the interface method between the human and the equipment/machine. An operator interface is the interface method by which multiple equipment that are linked by a host control system is accessed or controlled.
The system may expose several user interfaces to serve different kinds of users. For example, a computerized library database might provide two user interfaces, one for library patrons and the other for library personnel; the user interface of a mechanical system, a vehicle or an industrial installation is sometimes referred to as the human–machine interface. HMI is a modification of the original term MMI. In practice, the abbreviation MMI is still used although some may claim that MMI stands for something different now. Another abbreviation is HCI, but is more used for human–computer interaction. Other terms used are operator interface terminal; however it is abbreviated, the terms refer to the'layer' that separates a human, operating a machine from the machine itself. Without a clean and usable interface, humans would not be able to
The ZP-150 was one of the early commercially available portable computers. It was sold by Heathkit; the ZP-150 was offered for US$1995 when bundled with the $800 Microsoft Works software, but could be found in the Fall 1985 Heathkit catalog for US$1195. The price came down to $999 in the Winter 1986 edition of the same catalog and $699 in the Fall 1987 edition, as it was being phased out with the release of the Z-181 and Z-183; the main target market was the U. S. government and "the mobile executive", for on-site applications. Its small dimensions and light weight allowed it to be carried in a standard briefcase or the included carrying case. Weight: 7.7 lb Dimensions: 13"W × 11.1"D × 1.8"H RAM: 32K, expandable to 416K ROM: 224K, plus 2 sockets for software expansion CPU: Intel 80C88 Power: 12VDC or 10 AA alkaline batteries, plus internal nickel-cadmium battery for retaining memory while off, up to 8 days Ports:Parallel printer RS-232C Telephone line System bus BCR CMT ACP Handset LCD display, contrast control, volume control, low-battery indicator 75-key typewriter-style keyboardThe stock 32K RAM could hold up to 10 typewritten pages.
The main methods of file transfer were via the modem or the RS-232C port and a file transfer program. The ZP-150 came with a built-in System Manager and calculator program, as well as a special version of Microsoft Works 1.10 stored in ROM. Most programs are similar to the desktop versions, but with reduced functionality. Word word processor Plan electronic spreadsheet, similar to Multiplan Calendar appointment organizer with alarm File database manager Telcom telecommunications package BASIC program editor and compiler ZP-150-1 power transformer ZP-150-2 32K RAM module ZP-150-4 Parallel to Centronics printer cable CB-5063-27 File transfer software The most significant aspect of the ZP-150's history is that it is not remembered as one of the first portable computers, despite its early appearance in the marketplace and being referred to in advertising as a "laptop". Like the IBM PC and Apple II computers, the ZP-150 was copied; the most well-known clone is the Tandy 600, similar in packaging and hardware except for the addition of a floppy drive and the lacking of BASIC.
This was not the first laptop that Tandy was one in the TRS-80 line. History of computing hardware Laptop ZP-150 User's guide, Zenith Data Systems Corporation, St. Joseph, MI and Heath Company, Benton Arbor, MI Heathkit catalogs, Fall 1985 pp90-91, Winter 1986 p89, Fall 1987 p84 OLD-COMPUTERS.com Museum TRS-80 Model 600 8bit-Micro.com - TRS-80 Laptops IEEE Annals of the History of Computing Tandy 600 and Zenith ZP150 photographic comparison of the internal hardware of the Tandy 600 and the Zenith ZP-150 Zenith Data Systems company timeline "Zenith ZP-150, 360 degree model", Russian Vintage Laptop Museum
The Intel 80386 known as i386 or just 386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors and were the CPU of many workstations and high-end personal computers of the time; as the original implementation of the 32-bit extension of the 80286 architecture, the 80386 instruction set, programming model, binary encodings are still the common denominator for all 32-bit x86 processors, termed the i386-architecture, x86, or IA-32, depending on context. The 32-bit 80386 can execute most code intended for the earlier 16-bit processors such as 8086 and 80286 that were ubiquitous in early PCs. Over the years, successively newer implementations of the same architecture have become several hundreds of times faster than the original 80386. A 33 MHz 80386 was measured to operate at about 11.4 MIPS. The 80386 was introduced in October 1985, while manufacturing of the chips in significant quantities commenced in June 1986. Mainboards for 80386-based computer systems were cumbersome and expensive at first, but manufacturing was rationalized upon the 80386's mainstream adoption.
The first personal computer to make use of the 80386 was designed and manufactured by Compaq and marked the first time a fundamental component in the IBM PC compatible de facto standard was updated by a company other than IBM. In May 2006, Intel announced that 80386 production would stop at the end of September 2007. Although it had long been obsolete as a personal computer CPU, Intel and others had continued making the chip for embedded systems; such systems using an 80386 or one of many derivatives are common in aerospace technology and electronic musical instruments, among others. Some mobile phones used the 80386 processor, such as BlackBerry 950 and Nokia 9000 Communicator; the processor was a significant evolution in the x86 architecture, extended a long line of processors that stretched back to the Intel 8008. The predecessor of the 80386 was the Intel 80286, a 16-bit processor with a segment-based memory management and protection system; the 80386 added a 32-bit architecture and a paging translation unit, which made it much easier to implement operating systems that used virtual memory.
It offered support for register debugging. The 80386 featured three operating modes: protected mode and virtual mode; the protected mode, which debuted in the 286, was extended to allow the 386 to address up to 4 GB of memory. The all new virtual 8086 mode made it possible to run one or more real mode programs in a protected environment, although some programs were not compatible; the ability for a 386 to be set up to act like it had a flat memory model in protected mode despite the fact that it uses a segmented memory model in all modes would arguably be the most important feature change for the x86 processor family until AMD released x86-64 in 2003. Several new instructions have been added to 386: BSF, BSR, BT, BTS, BTR, BTC, CDQ, CWDE, LFS, LGS, LSS, MOVSX, MOVZX, SETcc, SHLD, SHRD. Two new segment registers have been added for general-purpose programs, single Machine Status Word of 286 grew into eight control registers CR0–CR7. Debug registers DR0–DR7 were added for hardware breakpoints. New forms of MOV instruction are used to access them.
Chief architect in the development of the 80386 was John H. Crawford, he was responsible for extending the 80286 architecture and instruction set to 32-bit, led the microprogram development for the 80386 chip. The 80486 and P5 Pentium line of processors were descendants of the 80386 design; the following data types are directly supported and thus implemented by one or more 80386 machine instructions. 8-bit integer, either signed or unsigned. 16-bit integer, either signed or unsigned. 32-bit integer, either signed or unsigned. 64-bit integer, either signed or unsigned. Offset, a 16- or 32-bit displacement referring to a memory location. Pointer, a 16-bit selector together with a 16- or 32-bit offset. Character. String, a sequence of 8-, 16- or 32-bit words. BCD, decimal digits represented by unpacked bytes. Packed BCD, two BCD digits in one byte; the following 80386 assembly source code is for a subroutine named _strtolower that copies a null-terminated ASCIIZ character string from one location to another, converting all alphabetic characters to lower case.
The string is copied one byte at a time. The example code uses the EBP register to establish a call frame, an area on the stack that contains all of the parameters and local variables for the execution of the subroutine; this kind of calling convention supports reentrant and recursive code and has been used by Algol-like languages since the late 1950s. A flat memory model is assumed that the DS and ES segments address the same region of memory. In 1988, Intel introduced the 80386SX, most referred to as the 386SX, a cut-down version of the 80386 with a 16-bit data bus intended for lower-cost PCs aimed at the home and small-business markets, while the 386DX would remain the high-end variant used in workstations and other demanding tasks; the CPU remained 32-bit internally, but the 16-bit
MS-DOS is an operating system for x86-based personal computers developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, some operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS". MS-DOS was the main operating system for IBM PC compatible personal computers during the 1980s and the early 1990s, when it was superseded by operating systems offering a graphical user interface, in various generations of the graphical Microsoft Windows operating system. MS-DOS was the result of the language developed in the seventies, used by IBM for its mainframe operating system. Microsoft acquired the rights to meet IBM specifications. IBM re-released it on August 12, 1981 as PC DOS 1.0 for use in their PCs. Although MS-DOS and PC DOS were developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility and capabilities. During its lifetime, several competing products were released for the x86 platform, MS-DOS went through eight versions, until development ceased in 2000.
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 greater sizes and formats, along with added feature support for newer processors and evolving computer architectures, it was the key product in Microsoft's growth from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was the underlying basic operating system on which early versions of Windows ran as a GUI, it is a flexible operating system, consumes negligible installation space. 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 a clone of Digital Research's CP/M, ported to run on 8086 processors and with two notable differences compared to CP/M.
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 $75,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS, they licensed MS-DOS 1.10/1.14 to IBM, who, 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. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers, minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, 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 supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, there is a major distinction between an IBM-compatible machine and an MS-DOS machine; some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could run software written 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, indeed the same design philosophy is embodied in Windows NT. However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance for games, which pushed the limits of their contemporary hardware. Soon an IBM-compatible architecture became the goal, before long all 8086-family computers emulated IBM's hardware, 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, discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, in any case were 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 —with a few notable exceptions. Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix-based operating system, was multi-user; the company planned, over time, to improve MS-DOS so it would be indistinguishable from single-user Xenix, or XEDOS, which would run on the Motorola 68000, Zilog Z8000, the LSI-11. 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", promising easy