Operating system

An operating system (OS) is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system. A user cannot run an application program on the computer without an operating system, unless the application program is self booting.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and the computer hardware, [ 1 ] [ 2 ] although the application code is usually executed directly by the hardware and will frequently call the OS or be interrupted by it. Operating systems are found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems include Android, iOS, Linux, Mac OS X, and Microsoft Windows. [ 3 ]

Contents

Types

Summary

Early computers were built to perform a series of single tasks, like a calculator. Operating systems did not exist in their modern and more complex forms until the early 1960s. [ 4 ] Some operating system features were developed in the 1950s, such as monitor programs that could automatically run different application programs in succession to speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers by companies such as Apple Inc., Atari, IBM and Amiga became popular in the 1980s, vendors added operating system features that had previously become widely used on mainframe and mini computers. Later, many features such as graphical user interface were developed specifically for personal computer operating systems.

An operating system consists of many parts. One of the most important components is the kernel, which controls low-level processes that the average user usually cannot see: it controls how memory is read and written, the order in which processes are executed, how information is received and sent by devices like the monitor, keyboard and mouse, and decides how to interpret information received from networks. The user interface is a component that interacts with the computer user directly, allowing them to control and use programs. The user interface may be graphical with icons and a desktop, or textual, with a command line. Application programming interfaces provide services and code libraries that let applications developers write modular code reusing well defined programming sequences in user space libraries or in the operating system itself. Which features are considered part of the operating system is defined differently in various operating systems. For example, Microsoft Windows considers its user interface to be part of the operating system, while many versions of Linux do not.

History

In the 1940s, the earliest electronic digital systems had no operating systems. Electronic systems of this time were so primitive compared to those of today that instructions were often entered into the system one bit at a time on rows of mechanical switches or by jumper wires on plug boards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the printing of payroll checks from data on punched paper cards. After programmable general purpose computers were invented, machine languages (consisting of strings of the binary digits 0 and 1 on punched paper tape) were introduced that speed up the programming process (Stern, 1981).

In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer for a limited period of time and would arrive at a scheduled time with program and data on punched paper cards and/or punched tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine. [ citation needed ]

Later machines came with libraries of software, which would be linked to a user’s program to assist in operations such as input and output and generating computer code from human-readable symbolic code. This was the genesis of the modern-day operating system. However, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different colored clothes-pegs to indicate job-priority. [ citation needed ]

Mainframes

Through the 1950s, many major features were pioneered in the field of operating systems, including batch processing, input/output interrupt, buffering, multitasking, spooling, runtime libraries, link-loading, and programs for sorting records in files. These features were included or not included in application software at the option of application programmers, rather than in a separate operating system used by all applications. In 1959 the SHARE Operating System was released as an integrated utility for the IBM 704, and later in the 709 and 7090 mainframes, although it was quickly supplanted by IBSYS/IBJOB on the 709, 7090 and 7094.

During the 1960s, IBM’s OS/360 introduced the concept of a single OS spanning an entire product line, which was crucial for the success of the System/360 machines. IBM’s current mainframe operating systems are distant descendants of this original system and applications written for OS/360 can still be run on modern machines. [ citation needed ]

OS/360 also pioneered the concept that the operating system keeps track of all of the system resources that are used, including program and data space allocation in main memory and file space in secondary storage, and file locking during update. When the process is terminated for any reason, all of these resources are re-claimed by the operating system.

The alternative CP-67 system for the S/360-67 started a whole line of IBM operating systems focused on the concept of virtual machines. Other operating systems used on IBM S/360 series mainframes included systems developed by IBM: COS/360 (Compatabililty Operating System), DOS/360 (Disk Operating System), TSS/360 (Time Sharing System), TOS/360 (Tape Operating System), BOS/360 (Basic Operating System), and ACP (Airline Control Program), as well as a few non-IBM systems: MTS (Michigan Terminal System), MUSIC (Multi-User System for Interactive Computing), and ORVYL (Stanford Timesharing System).

Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In cooperation with the University of Minnesota, the Kronos and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. Burroughs Corporation introduced the B5000 in 1961 with the MCP, (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages with no machine language or assembler, and indeed the MCP was the first OS to be written exclusively in a high-level language – ESPOL, a dialect of ALGOL. MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation of virtual memory. During development of the AS400, IBM made an approach to Burroughs to licence MCP to run on the AS400 hardware. This proposal was declined by Burroughs management to protect its existing hardware production. MCP is still in use today in the Unisys ClearPath/MCP line of computers.

UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this was a batch-oriented system that managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BC system.

General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed to General Comprehensive Operating System (GCOS).

Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Prior to the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community.

In the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in order to permit different underlying architecture to appear to be the same as others in a series. In fact most 360s after the 360/40 (except the 360/165 and 360/168) were microprogrammed implementations. But soon other means of achieving application compatibility were proven to be more significant.

The enormous investment in software for these systems made since 1960s caused most of the original computer manufacturers to continue to develop compatible operating systems along with the hardware. The notable supported mainframe operating systems include:

• Burroughs MCP – B5000, 1961 to Unisys Clearpath/MCP, present.
• IBM OS/360 – IBM System/360, 1966 to IBM z/OS, present.
• IBM CP-67 – IBM System/360, 1967 to IBM z/VM, present.
• UNIVAC EXEC 8 – UNIVAC 1108, 1967, to OS 2200 Unisys Clearpath Dorado, present.

Microsoft Windows

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Microsoft Windows, also called Windows and Windows OS, computer operating system (OS) developed by Microsoft Corporation to run personal computers (PCs). Featuring the first graphical user interface (GUI) for IBM-compatible PCs, the Windows OS soon dominated the PC market. Approximately 90 percent of PCs run some version of Windows.

The first version of Windows, released in 1985, was simply a GUI offered as an extension of Microsoft’s existing disk operating system, or MS-DOS. Based in part on licensed concepts that Apple Inc. had used for its Macintosh System Software, Windows for the first time allowed DOS users to visually navigate a virtual desktop, opening graphical “windows” displaying the contents of electronic folders and files with the click of a mouse button, rather than typing commands and directory paths at a text prompt.

Subsequent versions introduced greater functionality, including native Windows File Manager, Program Manager, and Print Manager programs, and a more dynamic interface. Microsoft also developed specialized Windows packages, including the networkable Windows for Workgroups and the high-powered Windows NT, aimed at businesses. The 1995 consumer release Windows 95 fully integrated Windows and DOS and offered built-in Internet support, including the World Wide Web browser Internet Explorer.

With the 2001 release of Windows XP, Microsoft united its various Windows packages under a single banner, offering multiple editions for consumers, businesses, multimedia developers, and others. Windows XP abandoned the long-used Windows 95 kernel (core software code) for a more powerful code base and offered a more practical interface and improved application and memory management. The highly successful XP standard was succeeded in late 2006 by Windows Vista, which experienced a troubled rollout and met with considerable marketplace resistance, quickly acquiring a reputation for being a large, slow, and resource-consuming system. Responding to Vista’s disappointing adoption rate, Microsoft in 2009 released Windows 7, an OS whose interface was similar to that of Vista but was met with enthusiasm for its noticeable speed improvement and its modest system requirements.

Windows 8 in 2012 offered a start screen with applications appearing as tiles on a grid and the ability to synchronize settings so users could log on to another Windows 8 machine and use their preferred settings. In 2015 Microsoft released Windows 10, which came with Cortana, a digital personal assistant like Apple’s Siri, and the Web browser Microsoft Edge, which replaced Internet Explorer. Microsoft also announced that Windows 10 would be the last version of Windows, meaning that users would receive regular updates to the OS but that no more large-scale revisions would be done.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Amy Tikkanen, Corrections Manager.

Microsoft’s Windows operating system

In 1985 Microsoft came out with its Windows operating system, which gave PC compatibles some of the same capabilities as the Macintosh. Year after year, Microsoft refined and improved Windows so that Apple, which failed to come up with a significant new advantage, lost its edge. IBM tried to establish yet another operating system, OS/2, but lost the battle to Gates’s company. In fact, Microsoft also had established itself as the leading provider of application software for the Macintosh. Thus Microsoft dominated not only the operating system and application software business for PC-compatibles but also the application software business for the only nonstandard system with any sizable share of the desktop computer market. In 1998, amid a growing chorus of complaints about Microsoft’s business tactics, the U.S. Department of Justice filed a lawsuit charging Microsoft with using its monopoly position to stifle competition.

Workstation computers

While the personal computer market grew and matured, a variation on its theme grew out of university labs and began to threaten the minicomputers for their market. The new machines were called workstations. They looked like personal computers, and they sat on a single desktop and were used by a single individual just like personal computers, but they were distinguished by being more powerful and expensive, by having more complex architectures that spread the computational load over more than one CPU chip, by usually running the UNIX operating system, and by being targeted to scientists and engineers, software and chip designers, graphic artists, moviemakers, and others needing high performance. Workstations existed in a narrow niche between the cheapest minicomputers and the most powerful personal computers, and each year they had to become more powerful, pushing at the minicomputers even as they were pushed at by the high-end personal computers.

The most successful of the workstation manufacturers were Sun Microsystems, Inc., started by people involved in enhancing the UNIX operating system, and, for a time, Silicon Graphics, Inc., which marketed machines for video and audio editing.

The microcomputer market now included personal computers, software, peripheral devices, and workstations. Within two decades this market had surpassed the market for mainframes and minicomputers in sales and every other measure. As if to underscore such growth, in 1996 Silicon Graphics, a workstation manufacturer, bought the star of the supercomputer manufacturers, Cray Research, and began to develop supercomputers as a sideline. Moreover, Compaq Computer Corporation—which had parlayed its success with portable PCs into a perennial position during the 1990s as the leading seller of microcomputers—bought the reigning king of the minicomputer manufacturers, Digital Equipment Corporation (DEC). Compaq announced that it intended to fold DEC technology into its own expanding product line and that the DEC brand name would be gradually phased out. Microcomputers were not only outselling mainframes and minis, they were blotting them out.

Living in cyberspace

Ever smaller computers

Embedded systems

One can look at the development of the electronic computer as occurring in waves. The first large wave was the mainframe era, when many people had to share single machines. (The mainframe era is covered in the section The age of Big Iron.) In this view, the minicomputer era can be seen as a mere eddy in the larger wave, a development that allowed a favoured few to have greater contact with the big machines. Overall, the age of mainframes could be characterized by the expression “Many persons, one computer.”

The second wave of computing history was brought on by the personal computer, which in turn was made possible by the invention of the microprocessor. (This era is described in the section The personal computer revolution.) The impact of personal computers has been far greater than that of mainframes and minicomputers: their processing power has overtaken that of the minicomputers, and networks of personal computers working together to solve problems can be the equal of the fastest supercomputers. The era of the personal computer can be described as the age of “One person, one computer.”

Since the introduction of the first personal computer, the semiconductor business has grown to more than a quarter-trillion-dollar worldwide industry. However, this phenomenon is only partly ascribable to the general-purpose microprocessor, which accounts for about one-sixth of annual sales. The greatest growth in the semiconductor industry has occurred in the manufacture of special-purpose processors, controllers, and digital signal processors. These computer chips are increasingly being included, or embedded, in a vast array of consumer devices, including pagers, mobile telephones, music players, automobiles, televisions, digital cameras, kitchen appliances, video games, and toys. While the Intel Corporation may be safely said to dominate the worldwide microprocessor business, it has been outpaced in this rapidly growing multibillion-dollar industry by companies such as Motorola, Inc.; Hitachi, Ltd.; Texas Instruments Incorporated; NEC Corporation; and Lucent Technologies Inc. This ongoing third wave may be characterized as “One person, many computers.”

Handheld digital devices

The origins of handheld digital devices go back to the 1960s, when Alan Kay, a researcher at Xerox’s Palo Alto Research Center (PARC), promoted the vision of a small, powerful notebook-style computer that he called the Dynabook. Kay never actually built a Dynabook (the technology had yet to be invented), but his vision helped to catalyze the research that would eventually make his dream feasible.

It happened by small steps. The popularity of the personal computer and the ongoing miniaturization of the semiconductor circuitry and other devices first led to the development of somewhat smaller, portable—or, as they were sometimes called, luggable—computer systems. The first of these, the Osborne 1, designed by Lee Felsenstein, an electronics engineer active in the Homebrew Computer Club in San Francisco, was sold in 1981. Soon most PC manufacturers had portable models. At first these portables looked like sewing machines and weighed in excess of 20 pounds (9 kg). Gradually they became smaller (laptop-, notebook-, and then sub-notebook-size) and came with more powerful processors. These devices allowed people to use computers not only in the office or at home but also while traveling—on airplanes, in waiting rooms, or even at the beach.

As the size of computers continued to shrink and microprocessors became more and more powerful, researchers and entrepreneurs explored new possibilities in mobile computing. In the late 1980s and early ’90s, several companies came out with handheld computers, called personal digital assistants (PDAs). PDAs typically replaced the cathode-ray-tube screen with a more compact liquid crystal display, and they either had a miniature keyboard or replaced the keyboard with a stylus and handwriting-recognition software that allowed the user to write directly on the screen. Like the first personal computers, PDAs were built without a clear idea of what people would do with them. In fact, people did not do much at all with the early models. To some extent, the early PDAs, made by Go Corporation and Apple, were technologically premature; with their unreliable handwriting recognition, they offered little advantage over paper-and-pencil planning books.

The potential of this new kind of device was realized in 1996 when Palm Computing, Inc., released the Palm Pilot, which was about the size of a deck of playing cards and sold for about $400—approximately the same price as the MITS Altair, the first personal computer sold as a kit in 1974. The Pilot did not try to replace the computer but made it possible to organize and carry information with an electronic calendar, telephone number and address list, memo pad, and expense-tracking software and to synchronize that data with a PC. The device included an electronic cradle to connect to a PC and pass information back and forth. It also featured a data-entry system called “graffiti,” which involved writing with a stylus using a slightly altered alphabet that the device recognized. Its success encouraged numerous software companies to develop applications for it.

In 1998 this market heated up further with the entry of several established consumer electronics firms using Microsoft’s Windows CE operating system (a stripped-down version of the Windows system) to sell handheld computer devices and wireless telephones that could connect to PCs. These small devices also often possessed a communications component and benefited from the sudden popularization of the Internet and the World Wide Web. In particular, the BlackBerry PDA, introduced by the Canadian company Research in Motion in 2002, established itself as a favourite in the corporate world because of features that allowed employees to make secure connections with their company’s databases.

In 2001 Apple introduced the iPod, a handheld device capable of storing 1,000 songs for playback. Apple quickly came to dominate a booming market for music players. The iPod could also store notes and appointments. In 2003 Apple opened an online music store, iTunes Store, and in the following software releases added photographs and movies to the media the iPod could handle. The market for iPods and iPod-like devices was second only to cellular telephones among handheld electronic devices.

While Apple and competitors grew the market for handheld devices with these media players, mobile telephones were increasingly becoming “smartphones,” acquiring more of the functions of computers, including the ability to send and receive e-mail and text messages and to access the Internet. In 2007 Apple once again shook up a market for handheld devices, this time redefining the smartphone market with its iPhone. The touch-screen interface of the iPhone was in its way more advanced than the graphical user interface used on personal computers, its storage rivaled that of computers from just a few years before, and its operating system was a modified version of the operating system on the Apple Macintosh. This, along with synchronizing and distribution technology, embodied a vision of ubiquitous computing in which personal documents and other media could be moved easily from one device to another. Handheld devices and computers found their link through the Internet.