Architecture (562409), страница 13
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E-mail has had a great impact on the amount of information sent worldwide. It has become an important method of transmitting information previously relayed via regular mail, telephone, courier, fax, television, and radio.
Windows
Windows, in computer science, personal computer operating system sold by Microsoft Corporation that allows users to enter commands with a point-and-click device, such as a mouse, instead of a keyboard. An operating system is a set of programs that control the basic functions of a computer. The Windows operating system provides users with a graphical user interface (GUI), which allows them to manipulate small pictures, called icons, on the computer screen to issue commands. Windows is the most widely used operating system in the world. It is an extension of and replacement for Microsoft’s Disk Operating System (MS-DOS).
The Windows GUI is designed to be a natural, or intuitive, work environment for the user. With Windows, the user can move a cursor around on the computer screen with a mouse. By pointing the cursor at icons and clicking buttons on the mouse, the user can issue commands to the computer to perform an action, such as starting a program, accessing a data file, or copying a data file. Other commands can be reached through pull-down or click-on menu items. The computer displays the active area in which the user is working as a window on the computer screen. The currently active window may overlap with other previously active windows that remain open on the screen. This type of GUI is said to include WIMP features: windows, icons, menus, and pointing device (such as a mouse).
Computer scientists at the Xerox Corporation’s Palo Alto Research Center (PARC) invented the GUI concept in the early 1970s, but this innovation was not an immediate commercial success. In 1983 Apple Computer featured a GUI in its Lisa computer. This GUI was updated and improved in its Macintosh computer, introduced in 1984.
Microsoft began its development of a GUI in 1983 as an extension of its MS-DOS operating system. Microsoft’s Windows version 1.0 first appeared in 1985. In this version, the windows were tiled, or presented next to each other rather than overlapping. Windows version 2.0, introduced in 1987, was designed to resemble IBM’s OS/2 Presentation Manager, another GUI operating system. Windows version 2.0 included the overlapping window feature. The more powerful version 3.0 of Windows, introduced in 1990, and subsequent versions 3.1 and 3.11 rapidly made Windows the market leader in operating systems for personal computers, in part because it was prepackaged on new personal computers. It also became the favored platform for software development.
In 1993 Microsoft introduced Windows NT (New Technology). The Windows NT operating system offers 32-bit multitasking, which gives a computer the ability to run several programs simultaneously, or in parallel, at high speed. This operating system competes with IBM’s OS/2 as a platform for the intensive, high-end, networked computing environments found in many businesses.
In 1995 Microsoft released a new version of Windows for personal computers called Windows 95. Windows 95 had a sleeker and simpler GUI than previous versions. It also offered 32-bit processing, efficient multitasking, network connections, and Internet access. Windows 98, released in 1998, improved upon Windows 95.
In 1996 Microsoft debuted Windows CE, a scaled-down version of the Microsoft Windows platform designed for use with handheld personal computers. Windows 2000, released at the end of 1999, combined Windows NT technology with the Windows 98 graphical user interface.
Other popular operating systems include the Macintosh System (Mac OS) from Apple Computer, Inc., OS/2 Warp from IBM, and UNIX and its variations, such as Linux.
Operating System
| I | INTRODUCTION |
Operating System (OS), in computer science, the basic software that controls a computer. The operating system has three major functions: It coordinates and manipulates computer hardware, such as computer memory, printers, disks, keyboard, mouse, and monitor; it organizes files on a variety of storage media, such as floppy disk, hard drive, compact disc, and tape; and it manages hardware errors and the loss of data.
| II | HOW AN OS WORKS |
Operating systems control different computer processes, such as running a spreadsheet program or accessing information from the computer's memory. One important process is the interpretation of commands that allow the user to communicate with the computer. Some command interpreters are text oriented, requiring commands to be typed in. Other command interpreters are graphically oriented and let the user communicate by pointing and clicking on an icon, an on-screen picture that represents a specific command. Beginners generally find graphically oriented interpreters easier to use, but many experienced computer users prefer text-oriented command interpreters because they are more powerful.
Operating systems are either single-tasking or multitasking. The more primitive single-tasking operating systems can run only one process at a time. For instance, when the computer is printing a document, it cannot start another process or respond to new commands until the printing is completed.
All modern operating systems are multitasking and can run several processes simultaneously. In most computers there is only one central processing unit (CPU; the computational and control unit of the computer), so a multitasking OS creates the illusion of several processes running simultaneously on the CPU. The most common mechanism used to create this illusion is time-slice multitasking, whereby each process is run individually for a fixed period of time. If the process is not completed within the allotted time, it is suspended and another process is run. This exchanging of processes is called context switching. The OS performs the “bookkeeping” that preserves the state of a suspended process. It also has a mechanism, called a scheduler, that determines which process will be run next. The scheduler runs short processes quickly to minimize perceptible delay. The processes appear to run simultaneously because the user's sense of time is much slower than the processing speed of the computer.
Operating systems can use virtual memory to run processes that require more main memory than is actually available. With this technique, space on the hard drive is used to mimic the extra memory needed. Accessing the hard drive is more time-consuming than accessing main memory, however, so performance of the computer slows.
| III | CURRENT OPERATING SYSTEMS |
Operating systems commonly found on personal computers include UNIX, Macintosh OS, MS-DOS, OS/2, and Windows. UNIX, developed in 1969 at AT&T Bell Laboratories, is a popular operating system among academic computer users. Its popularity is due in large part to the growth of the interconnected computer network known as the Internet, the software for which initially was designed for computers that ran UNIX. Variations of UNIX include SunOS (distributed by SUN Microsystems, Inc.), Xenix (distributed by Microsoft Corporation), and Linux (available for download free of charge and distributed commercially by companies such as Red Hat, Inc.). UNIX and its clones support multitasking and multiple users. Its file system provides a simple means of organizing disk files and lets users protect their files from other users. The commands in UNIX are not intuitive, however, and mastering the system is difficult.
DOS (Disk Operating System) and its successor, MS-DOS, are popular operating systems among users of personal computers. The file systems of DOS and MS-DOS are similar to that of UNIX, but they are single user and single-tasking because they were developed before personal computers became relatively powerful. A multitasking variation is OS/2, initially developed by Microsoft Corporation and International Business Machines (IBM).
Few computer users run MS-DOS or OS/2 directly. They prefer versions of UNIX or windowing systems with graphical interfaces, such as Windows or the Macintosh OS, which make computer technology more accessible. However, graphical systems generally have the disadvantage of requiring more hardware—such as faster CPUs, more memory, and higher-quality monitors—than do command-oriented operating systems.
| IV | FUTURE TECHNOLOGIES |
Operating systems continue to evolve. A recently developed type of OS called a distributed operating system is designed for a connected, but independent, collection of computers that share resources such as hard drives. In a distributed OS, a process can run on any computer in the network (presumably a computer that is idle) to increase that process's performance. All basic OS functions—such as maintaining file systems, ensuring reasonable behavior, and recovering data in the event of a partial failure—become more complex in distributed systems.
Research is also being conducted that would replace the keyboard with a means of using voice or handwriting for input. Currently these types of input are imprecise because people pronounce and write words very differently, making it difficult for a computer to recognize the same input from different users. However, advances in this field have led to systems that can recognize a small number of words spoken by a variety of people. In addition, software has been developed that can be taught to recognize an individual's handwriting.
International Business Machines Corporation
| I | INTRODUCTION |
International Business Machines Corporation (IBM), one of the world’s largest manufacturers of computers and a leading provider of computer-related products and services worldwide. IBM makes computer hardware, software, microprocessors, communications systems, servers, and workstations. Its products are used in business, government, science, defense, education, medicine, and space exploration. IBM has its headquarters in Armonk, New York.
| II | ORIGINS |
The company was incorporated in 1911 as Computing-Tabulating-Recording Company in a merger of three smaller companies. After further acquisitions, it absorbed the International Business Machines Corporation in 1924 and assumed that company’s name. Thomas Watson arrived that same year and began to build the floundering company into an industrial giant. IBM soon became the country’s largest manufacturer of time clocks and punch-card tabulators. It also developed and marketed the first electric typewriter.
| III | DIGITAL COMPUTERS |
IBM entered the market for digital computers in the early 1950s, after the introduction of the UNIVAC computer by rival Remington Rand in 1951. The development of IBM’s computer technology was largely funded by contracts with the U.S. government’s Atomic Energy Commission, and close parallels existed between products made for government use and those introduced by IBM into the public marketplace. In the late 1950s IBM distinguished itself with two innovations: the concept of a family of computers (its 360 family) in which the same software could be run across the entire family; and a corporate policy dictating that no customer would be allowed to fail in implementing an IBM system. This policy spawned enormous loyalty to “Big Blue,” as IBM came to be known.
IBM’s dominant position in the computer industry has led the U.S. Department of Justice to file several antitrust suits against the company. IBM lost an antitrust case in 1936, when the Supreme Court of the United States ruled that IBM and Remington Rand were unfairly controlling the punch-card market and illegally forcing customers to buy their products. In 1956 IBM settled another lawsuit filed by the Department of Justice. IBM agreed to sell its tabulating machines rather than just leasing them, to establish a competitive market for used machines. In 1982 the Justice Department abandoned a federal antitrust suit against IBM after 13 years of litigation.
From the 1960s until the 1980s IBM dominated the global market for mainframe computers, although in the 1980s IBM lost market share to other manufacturers in specialty areas such as high-performance computing. When minicomputers were introduced in the 1970s IBM viewed them as a threat to the mainframe market and failed to recognize their potential, opening the door for such competitors as Digital Equipment Corporation, Hewlett-Packard Company, and Data General.
| IV | IBM PC |
In 1981 IBM introduced its first personal computer, the IBM PC, which was rapidly adopted in businesses and homes. The computer was based on the 8088 microprocessor made by Intel Corporation and the MS-DOS operating system made by Microsoft Corporation. The PC’s enormous success led to other models, including the XT and AT lines. Seeking to capture a share of the personal-computer market, other companies developed clones of the PC, known as IBM-compatibles, that could run the same software as the IBM PC. By the mid-1980s these clone computers far outsold IBM personal computers.
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