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
DOS is a family of disk operating systems, hence the name. DOS consists of MS-DOS and a rebranded version under the name IBM PC DOS, both of which were introduced in 1981. Other compatible systems from other manufacturers include DR-DOS, ROM-DOS, PTS-DOS, FreeDOS. MS-DOS dominated the x86-based IBM PC compatible market between 1981 and 1995. Dozens of other operating systems use the acronym "DOS", including the mainframe DOS/360 from 1966. Others are Apple DOS, Apple ProDOS, Atari DOS, Commodore DOS, TRSDOS, AmigaDOS. Fictional operating systems have used this acronym as well, such as GLaDOS from the video game Portal. IBM PC DOS and its predecessor, 86-DOS, resembled Digital Research's CP/M—the dominant disk operating system for 8-bit Intel 8080 and Zilog Z80 microcomputers—but instead ran on Intel 8086 16-bit processors; when IBM introduced the IBM PC, built with the Intel 8088 microprocessor, they needed an operating system. Seeking an 8088-compatible build of CP/M, IBM approached Microsoft CEO Bill Gates.
IBM was sent to Digital Research, a meeting was set up. However, the initial negotiations for the use of CP/M broke down. Digital Research founder Gary Kildall refused, IBM withdrew. IBM again approached Bill Gates. Gates in turn approached Seattle Computer Products. There, programmer Tim Paterson had developed a variant of CP/M-80, intended as an internal product for testing SCP's new 16-bit Intel 8086 CPU card for the S-100 bus; the system was named QDOS, before being made commercially available as 86-DOS. Microsoft purchased 86-DOS for $50,000; this became Microsoft Disk Operating System, MS-DOS, introduced in 1981. Within a year Microsoft licensed MS-DOS to over 70 other companies, which supplied the operating system for their own hardware, sometimes under their own names. Microsoft required the use of the MS-DOS name, with the exception of the IBM variant. IBM continued to develop their version, PC DOS, for the IBM PC. Digital Research became aware that an operating system similar to CP/M was being sold by IBM, threatened legal action.
IBM responded by offering an agreement: they would give PC consumers a choice of PC DOS or CP/M-86, Kildall's 8086 version. Side-by-side, CP/M cost $200 more than PC DOS, sales were low. CP/M faded, with MS-DOS and PC DOS becoming the marketed operating system for PCs and PC compatibles. Microsoft sold MS-DOS only to original equipment manufacturers. One major reason for this was. DOS was structured such that there was a separation between the system specific device driver code and the DOS kernel. Microsoft provided an OEM Adaptation Kit which allowed OEMs to customize the device driver code to their particular system. By the early 1990s, most PCs adhered to IBM PC standards so Microsoft began selling MS-DOS in retail with MS-DOS 5.0. In the mid-1980s Microsoft developed a multitasking version of DOS; this version of DOS is referred to as "European MS-DOS 4" because it was developed for ICL and licensed to several European companies. This version of DOS supports preemptive multitasking, shared memory, device helper services and New Executable format executables.
None of these features were used in versions of DOS, but they were used to form the basis of the OS/2 1.0 kernel. This version of DOS is distinct from the released PC DOS 4.0, developed by IBM and based upon DOS 3.3. Digital Research attempted to regain the market lost from CP/M-86 with Concurrent DOS, FlexOS and DOS Plus with Multiuser DOS and DR DOS. Digital Research was bought by Novell, DR DOS became Novell DOS 7. Gordon Letwin wrote in 1995 that "DOS was, when we first wrote it, a one-time throw-away product intended to keep IBM happy so that they'd buy our languages". Microsoft expected; the company planned to over time improve MS-DOS so it would be indistinguishable from single-user Xenix, or XEDOS, which would run on the Motorola 68000, Zilog Z-8000, LSI-11. IBM, did not want to replace DOS. After AT&T began selling Unix, Microsoft and IBM began developing OS/2 as an alternative; the two companies had a series of disagreements over two successor operating systems to DOS, OS/2 and Windows.
They split development of their DOS systems as a result. The last retail version of MS-DOS was MS-DOS 6.22. The last retail version of PC DOS was PC DOS 2000, though IBM did develop PC DOS 7.10 for OEMs and internal use. The FreeDOS project began on 26 June 1994, when Microsoft announced it would no longer sell or support MS-DOS. Jim Hall posted a manifesto proposing the development of an open-source replacement. Within a few weeks, other programmers including Pat Villani and Tim Norman joined the project. A kernel, the COMMAND. COM command line interpreter, core utilities were created by pooling code they had wri
A personal computer is a multi-purpose computer whose size and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large costly minicomputer and mainframes, time-sharing by many people at the same time is not used with personal computers. Institutional or corporate computer owners in the 1960s had to write their own programs to do any useful work with the machines. While personal computer users may develop their own applications these systems run commercial software, free-of-charge software or free and open-source software, provided in ready-to-run form. Software for personal computers is developed and distributed independently from the hardware or operating system manufacturers. Many personal computer users no longer need to write their own programs to make any use of a personal computer, although end-user programming is still feasible; this contrasts with mobile systems, where software is only available through a manufacturer-supported channel, end-user program development may be discouraged by lack of support by the manufacturer.
Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the personal computer market, first with MS-DOS and with Microsoft Windows. Alternatives to Microsoft's Windows operating systems occupy a minority share of the industry; these include free and open-source Unix-like operating systems such as Linux. Advanced Micro Devices provides the main alternative to Intel's processors; the advent of personal computers and the concurrent Digital Revolution have affected the lives of people in all countries. "PC" is an initialism for "personal computer". The IBM Personal Computer incorporated the designation in its model name, it is sometimes useful to distinguish personal computers of the "IBM Personal Computer" family from personal computers made by other manufacturers. For example, "PC" is used in contrast with "Mac", an Apple Macintosh computer.. Since none of these Apple products were mainframes or time-sharing systems, they were all "personal computers" and not "PC" computers.
The "brain" may one day come down to our level and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far. In the history of computing, early experimental machines could be operated by a single attendant. For example, ENIAC which became operational in 1946 could be run by a single, albeit trained, person; this mode pre-dated the batch programming, or time-sharing modes with multiple users connected through terminals to mainframe computers. Computers intended for laboratory, instrumentation, or engineering purposes were built, could be operated by one person in an interactive fashion. Examples include such systems as the Bendix G15 and LGP-30of 1956, the Programma 101 introduced in 1964, the Soviet MIR series of computers developed from 1965 to 1969. By the early 1970s, people in academic or research institutions had the opportunity for single-person use of a computer system in interactive mode for extended durations, although these systems would still have been too expensive to be owned by a single person.
In what was to be called the Mother of All Demos, SRI researcher Douglas Engelbart in 1968 gave a preview of what would become the staples of daily working life in the 21st century: e-mail, word processing, video conferencing, the mouse. The demonstration required technical support staff and a mainframe time-sharing computer that were far too costly for individual business use at the time; the development of the microprocessor, with widespread commercial availability starting in the mid 1970's, made computers cheap enough for small businesses and individuals to own. Early personal computers—generally called microcomputers—were sold in a kit form and in limited volumes, were of interest to hobbyists and technicians. Minimal programming was done with toggle switches to enter instructions, output was provided by front panel lamps. Practical use required adding peripherals such as keyboards, computer displays, disk drives, printers. Micral N was the earliest commercial, non-kit microcomputer based on a microprocessor, the Intel 8008.
It was built starting in 1972, few hundred units were sold. This had been preceded by the Datapoint 2200 in 1970, for which the Intel 8008 had been commissioned, though not accepted for use; the CPU design implemented in the Datapoint 2200 became the basis for x86 architecture used in the original IBM PC and its descendants. In 1973, the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP based on the IBM PALM processor with a Philips compact cassette drive, small CRT, full function keyboard. SCAMP emulated an IBM 1130 minicomputer in order to run APL/1130. In 1973, APL was available only on mainframe computers, most desktop sized microcomputers such as the Wang 2200 or HP 9800 offered only BASIC; because SCAMP was the first to emulate APL/1130 performance on a portable, single user computer, PC Magazine in 1983 designated SCAMP a "revolutionary concept" and "the world's first personal computer". This seminal, single user portable computer now resides in the Smithsonian Institution, Washington, D.
C.. Successful demonstrations of the 1973 SCAMP prototype led to the IBM 5100 portable microcomputer launched in 1975 with the ability to be programmed in both APL and BASIC for engineers, analysts and other business problem-solvers. In the late 1960s such a machine would have been nearly as large as two desks and would have weigh
Microsoft Windows is a group of several graphical operating system families, all of which are developed and sold by Microsoft. Each family caters to a certain sector of the computing industry. Active Windows families include Windows Embedded. Defunct Windows families include Windows Mobile and Windows Phone. Microsoft introduced an operating environment named Windows on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces. Microsoft Windows came to dominate the world's personal computer market with over 90% market share, overtaking Mac OS, introduced in 1984. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh. On PCs, Windows is still the most popular operating system. However, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones.
In 2014, the number of Windows devices sold was less than 25 %. This comparison however may not be relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows show one third market share, similar to that for end user use; as of October 2018, the most recent version of Windows for PCs, tablets and embedded devices is Windows 10. The most recent versions for server computers is Windows Server 2019. A specialized version of Windows runs on the Xbox One video game console. Microsoft, the developer of Windows, has registered several trademarks, each of which denote a family of Windows operating systems that target a specific sector of the computing industry; as of 2014, the following Windows families are being developed: Windows NT: Started as a family of operating systems with Windows NT 3.1, an operating system for server computers and workstations. It now consists of three operating system subfamilies that are released at the same time and share the same kernel: Windows: The operating system for mainstream personal computers and smartphones.
The latest version is Windows 10. The main competitor of this family is macOS by Apple for personal computers and Android for mobile devices. Windows Server: The operating system for server computers; the latest version is Windows Server 2019. Unlike its client sibling, it has adopted a strong naming scheme; the main competitor of this family is Linux. Windows PE: A lightweight version of its Windows sibling, meant to operate as a live operating system, used for installing Windows on bare-metal computers, recovery or troubleshooting purposes; the latest version is Windows PE 10. Windows IoT: Initially, Microsoft developed Windows CE as a general-purpose operating system for every device, too resource-limited to be called a full-fledged computer. However, Windows CE was renamed Windows Embedded Compact and was folded under Windows Compact trademark which consists of Windows Embedded Industry, Windows Embedded Professional, Windows Embedded Standard, Windows Embedded Handheld and Windows Embedded Automotive.
The following Windows families are no longer being developed: Windows 9x: An operating system that targeted consumers market. Discontinued because of suboptimal performance. Microsoft now caters to the consumer market with Windows NT. Windows Mobile: The predecessor to Windows Phone, it was a mobile phone operating system; the first version was called Pocket PC 2000. The last version is Windows Mobile 6.5. Windows Phone: An operating system sold only to manufacturers of smartphones; the first version was Windows Phone 7, followed by Windows Phone 8, the last version Windows Phone 8.1. It was succeeded by Windows 10 Mobile; the term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are categorized as follows: The history of Windows dates back to 1981, when Microsoft started work on a program called "Interface Manager", it was announced in November 1983 under the name "Windows", but Windows 1.0 was not released until November 1985.
Windows 1.0 was to achieved little popularity. Windows 1.0 is not a complete operating system. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Cardfile, Clipboard viewer, Control Panel, Paint, Reversi and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples. Windows 2.0 was released in December 1987, was more popular than its predecessor. It features several improvements to the user memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0
In DOS memory management, expanded memory is a system of bank switching that provided additional memory to DOS programs beyond the limit of conventional memory. Expanded memory is an umbrella term for several incompatible technology variants; the most used variant was the Expanded Memory Specification, developed jointly by Lotus Software and Microsoft, so that this specification was sometimes referred to as "LIM EMS". LIM EMS had several versions; the first implemented version was EMS 3.2, which supported up to 8 MB of expanded memory and uses parts of the address space dedicated to communication with peripherals to map portions of the expanded memory. EEMS, an expanded-memory management standard competing with LIM EMS 3.x, was developed by AST Research and Ashton-Tate. EEMS was incorporated in LIM EMS 4.0, which supported up to 32 MB of expanded memory and provided some support for DOS multitasking as well. IBM, created its own expanded-memory standard called XMA; the use of expanded memory became common with games and business programs such as Lotus 1-2-3 in the late 1980s through the mid-1990s, but its use declined as users switched from DOS to protected-mode operating systems such as Linux, IBM OS/2, Microsoft Windows.
The 8088 processor of the IBM PC and IBM PC/XT could address one megabyte of memory. It inherited this limit from the 20-bit external address bus of the Intel 8086; the designers of the PC allocated the lower 640 kB of address space for read-write program memory, called "conventional memory", the remaining 384 kB of memory space was reserved for uses such as the system BIOS, video memory, memory on expansion peripheral boards. Though the IBM PC AT, introduced in 1984, used the 80286 chip that could address up to 16 MB of RAM as extended memory, it could only do so in protected mode; the scarcity of software compatible with the 286 protected mode meant that the market was still open for another solution. To fit much more memory than the 384 kB of free address space would allow, a bank switching scheme was devised, where only selected parts of the additional memory would be accessible at any given time. A single 64 kB window of memory, called a page frame, was possible. Programs had to be written in a specific way to access expanded memory.
The "window" between lower RAM and expanded RAM could be moved to different locations within the Expanded RAM. A first attempt to use a bank switching technique was made by Tall Tree Systems with their JRAM boards, but these did not catch on. Lotus Development and Microsoft cooperated to develop the EMS standard; the first publicly available version of EMS, version 3.0 allowed access of up to 4 MB of expanded memory. This was increased to 8 MB with version 3.2 of the specification. The final version of EMS, version 4.0 increased the maximum amount of expanded memory to 32 MB and supported additional functionality. Microsoft thought that bank switching was a inelegant and temporary, stopgap measure. It's a kludge!... But we're going to do it"; the companies planned to launch the standard at the Spring 1985 COMDEX, with many expansion-card and software companies announcing their support. The first public version of the EMS standard, called EMS 3.0 was released in 1985. EMS 3.2 used a 64 KB region in the upper 384 KB divided into four 16 KB pages, which could be used to map portions of the expanded memory.
In turn, EMS 3.2 was improved upon by a group of three other companies: AST Research and Ashton-Tate, which created their own Enhanced EMS standard. EEMS allowed any 16 KB region in lower RAM to be mapped to expanded memory, as long as it was not associated with interrupts or dedicated I/O memory such as network or video cards. Thus, entire programs could be switched in and out of the extra RAM. EEMS added support for two sets of mapping registers; these features were used by early DOS multitasker software such as DESQview. Released in 1987, the LIM EMS 4.0 specification incorporated all features of EEMS. A new feature added in LIM EMS 4.0 was that EMS boards could have multiple sets of page-mapping registers. This allowed a primitive form of DOS multitasking; the caveat was, that the standard did not specify how many register sets a board should have, so there was great variability between hardware implementations in this respect. The Expanded Memory Specification is the specification describing the use of expanded memory.
EMS functions are accessible through software interrupt 67h. Programs using EMS must first establish the presence of an installed expanded memory manager by checking for a device driver with the device name EMMXXXX0. IBM developed. SYS. Unlike EMS, the IBM expansion boards could be addressed both using an expanded memory model and as extended memory; the expanded memory hardware interface used by XMA boards is, incompatible with EMS, but a XMA2EMS. SYS driver provided EMS emulation for XMA boards. XMA boards were first introduced for the 1986 models of the 3270 PC; this insertion of a memory window into the peripheral address space could be accomplished only through specific expansion boards, plugged into the ISA expansion bus of the comput
Microsoft Corporation is an American multinational technology company with headquarters in Redmond, Washington. It develops, licenses and sells computer software, consumer electronics, personal computers, related services, its best known software products are the Microsoft Windows line of operating systems, the Microsoft Office suite, the Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface lineup of touchscreen personal computers; as of 2016, it is the world's largest software maker by revenue, one of the world's most valuable companies. The word "Microsoft" is a portmanteau of "microcomputer" and "software". Microsoft is ranked No. 30 in the 2018 Fortune 500 rankings of the largest United States corporations by total revenue. Microsoft was founded by Bill Gates and Paul Allen on April 4, 1975, to develop and sell BASIC interpreters for the Altair 8800, it rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Microsoft Windows.
The company's 1986 initial public offering, subsequent rise in its share price, created three billionaires and an estimated 12,000 millionaires among Microsoft employees. Since the 1990s, it has diversified from the operating system market and has made a number of corporate acquisitions, their largest being the acquisition of LinkedIn for $26.2 billion in December 2016, followed by their acquisition of Skype Technologies for $8.5 billion in May 2011. As of 2015, Microsoft is market-dominant in the IBM PC-compatible operating system market and the office software suite market, although it has lost the majority of the overall operating system market to Android; the company produces a wide range of other consumer and enterprise software for desktops and servers, including Internet search, the digital services market, mixed reality, cloud computing and software development. Steve Ballmer replaced Gates as CEO in 2000, envisioned a "devices and services" strategy; this began with the acquisition of Danger Inc. in 2008, entering the personal computer production market for the first time in June 2012 with the launch of the Microsoft Surface line of tablet computers.
Since Satya Nadella took over as CEO in 2014, the company has scaled back on hardware and has instead focused on cloud computing, a move that helped the company's shares reach its highest value since December 1999. In 2018, Microsoft surpassed Apple as the most valuable publicly traded company in the world after being dethroned by the tech giant in 2010. Childhood friends Bill Gates and Paul Allen sought to make a business utilizing their shared skills in computer programming. In 1972 they founded their first company, named Traf-O-Data, which sold a rudimentary computer to track and analyze automobile traffic data. While Gates enrolled at Harvard, Allen pursued a degree in computer science at Washington State University, though he dropped out of school to work at Honeywell; the January 1975 issue of Popular Electronics featured Micro Instrumentation and Telemetry Systems's Altair 8800 microcomputer, which inspired Allen to suggest that they could program a BASIC interpreter for the device. After a call from Gates claiming to have a working interpreter, MITS requested a demonstration.
Since they didn't yet have one, Allen worked on a simulator for the Altair while Gates developed the interpreter. Although they developed the interpreter on a simulator and not the actual device, it worked flawlessly when they demonstrated the interpreter to MITS in Albuquerque, New Mexico. MITS agreed to distribute it, marketing it as Altair BASIC. Gates and Allen established Microsoft on April 4, 1975, with Gates as the CEO; the original name of "Micro-Soft" was suggested by Allen. In August 1977 the company formed an agreement with ASCII Magazine in Japan, resulting in its first international office, "ASCII Microsoft". Microsoft moved to a new home in Bellevue, Washington in January 1979. Microsoft entered the operating system business in 1980 with its own version of Unix, called Xenix. However, it was MS-DOS. After negotiations with Digital Research failed, IBM awarded a contract to Microsoft in November 1980 to provide a version of the CP/M OS, set to be used in the upcoming IBM Personal Computer.
For this deal, Microsoft purchased a CP/M clone called 86-DOS from Seattle Computer Products, which it branded as MS-DOS, though IBM rebranded it to PC DOS. Following the release of the IBM PC in August 1981, Microsoft retained ownership of MS-DOS. Since IBM had copyrighted the IBM PC BIOS, other companies had to reverse engineer it in order for non-IBM hardware to run as IBM PC compatibles, but no such restriction applied to the operating systems. Due to various factors, such as MS-DOS's available software selection, Microsoft became the leading PC operating systems vendor; the company expanded into new markets with the release of the Microsoft Mouse in 1983, as well as with a publishing division named Microsoft Press. Paul Allen resigned from Microsoft in 1983 after developing Hodgkin's disease. Allen claimed that Gates wanted to dilute his share in the company when he was diagnosed with Hodgkin's disease because he didn't think he was working hard enough. After leaving Microsoft, Allen lost billions of dollars on ill-conceived or mistimed technology investments.
He invested in low-tech sectors, sports teams, commercial real estate. Despite having begun jointly developing a new operating system, OS/2, with IBM in
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