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Computer Technology
Computer, machine that performs tasks, such as mathematical calculations or electronic communication, under the control of a set of instructions called a program. Programs usually reside within the computer and are retrieved and processed by the computer electronics and the program results are stored or routed to output devices, such as video display monitors or printers. Computers are used to perform a wide variety of activities with reliability, accuracy, and speed.
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How Computer Works/
Hardware
The physical computer and its components are known as hardware. Computer hardware includes the memory that stores data and instructions; the central processing unit (CPU) that carries out instructions; the bus that connects the various computer components; the input devices, such as a keyboard or mouse, that allow the user to communicate with the computer; and the output devices, such as printers and video display monitors, that enable the computer to present information to the user. The programs that run the computer are called software. Software generally is designed to perform a particular type of task for example, to control the arm of a robot to weld a car body, to write a letter, to draw a graph, or to direct the general operation of the computer. |
Computer Memory
To process information electronically, data are stored in a computer in the form of binary digits, or bits, each having two possible representations (0 or 1).
A byte is a useful quantity in which to store information because it provides enough possible patterns to represent the entire alphabet, in lower and upper cases, as well as numeric digits, punctuation marks, and several character-sized graphics symbols, including non-English characters such as Ãà †â€™Ã †. A byte also can be interpreted as a pattern that represents a number between 0 and 255. A kilobyte 1,024 bytes can store about 1,000 characters; a megabyte can store about 1 million characters; a gigabyte can store about 1 billion characters; and a terabyte can store about 1 trillion characters.
The physical memory of a computer is either random access memory (RAM), which can be read or changed by the user or computer, or read-only memory (ROM), which can be read by the computer but not altered. One way to store memory is within the circuitry of the computer, usually in tiny computer chips that hold millions of bytes of information. The memory within these computer chips is RAM. Memory also can be stored outside the circuitry of the computer on external storage devices, such as magnetic floppy disks, which can store about 2 megabytes of information; hard drives, which can store thousands of megabytes of information; CD-ROMs (compact discs), which can store up to 630 megabytes of information; and DVDs (digital video discs), which can store 8.5 gigabytes of information. A single CD-ROM can store nearly as much information as 700 floppy disks can, and a DVD can hold 15 times as much data as a CD-ROM.
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Operating System
When a computer is turned on it searches for instructions in its memory. Usually, the first set of these instructions is a special program called the operating system, which is the software that makes the computer work. It prompts the user (or other machines) for input and commands, reports the results of these commands and other operations, stores and manages data, and controls the sequence of the software and hardware actions. When the user requests that a program run, the operating system loads the program in the computer memory and runs the program. Popular operating systems, such as Microsoft Windows and the Macintosh system (Mac OS), have a graphical user interface (GUI)that is, a display that uses tiny pictures, or icons, to represent various commands. To execute these commands, the user clicks the mouse on the icon or presses a combination of keys on the keyboard.
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Computer Languages
Programming languages contain the series of commands that create software. In general, a language that is encoded in binary numbers or a language similar to binary numbers that a computer hardware understands is understood more quickly by the computer. A program written in this type of language also runs faster. Languages that use words or other commands that reflect how humans think are easier for programmers to use, but they are slower because the language must be translated first so the computer can understand it.
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Networks
Computers can communicate with other computers through a series of connections and associated hardware called a network. The advantage of a network is that data can be exchanged rapidly, and software and hardware resources, such as hard-disk space or printers, can be shared.
One type of network, a local area network (LAN), consists of several PCs or workstations connected to a special computer called the server. The server stores and manages programs and data. A server often contains all of a networked group data and enables LAN workstations to be set up without storage capabilities to reduce cost.
Mainframe computers and supercomputers commonly are networked. They may be connected to PCs, workstations, or terminals that have no computational abilities of their own. These dum terminals are used only to enter data into, or receive output from, the central computer.
Wide area networks (WANs) are networks that span large geographical areas. Computers can connect to these networks to use facilities in another city or country. For example, a person in Los Angeles can browse through the computerized archives of the Library of Congress in Washington, D.C. The largest WAN is the Internet, a global consortium of networks linked by common communication programs.
The Internet is a mammoth resource of data, programs, and utilities. It was created mostly by American computer scientist Vinton Cerf in 1973 as part of the United States Department of Defense Advanced Research Projects Agency (DARPA). In 1984 the development of Internet technology was turned over to private, government, and scientific agencies. The World Wide Web, developed in the 1980s by British physicist Timothy Berners-Lee, is a system of information resources accessed primarily through the Internet. Users can obtain a variety of information in the form of text, graphics, sounds, or animations. These data are extensively cross-indexed, enabling users to browse (transfer from one information site to another) via buttons, highlighted text, or sophisticated searching software known as search engines.
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Machine Language
Computer programs that can be run by a computer operating system are called executables. An executable program is a sequence of extremely simple instructions known as machine code. These instructions are specific to the individual computer CPU and associated hardware; for example, Intel Pentium and Power PC microprocessor chips each have different machine languages and require different sets of codes to perform the same task. Machine code instructions are few in number (roughly 20 to 200, depending on the computer and the CPU). Typical instructions are for copying data from a memory location or for adding the contents of two memory locations (usually registers in the CPU). Machine code instructions are binary that is, sequences of bits (0s and 1s). Because these numbers are not understood easily by humans, computer instructions usually are not written in machine code.
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Internet
Internet, computer-based global information system. The Internet is composed of many interconnected computer networks. Each network may link tens, hundreds, or even thousands of computers, enabling them to share information with one another and to share computational resources such as powerful supercomputers and databases of information. The Internet has made it possible for people all over the world to effectively and inexpensively communicate with one another. Unlike traditional broadcasting media, such as radio and television, the Internet does not have a centralized distribution system. Instead, an individual who has Internet access can communicate directly with anyone else on the Internet, make information available to others, find information provided by others, or sell products with a minimum overhead cost.
The Internet has brought new opportunities to government, business, and education. Governments use the Internet for internal communication, distribution of information, and automated tax processing. In addition to offering goods and services online to customers, businesses use the Internet to interact with other businesses. Many individuals use the Internet for shopping, paying bills, and online banking. Educational institutions use the Internet for research and to deliver courses to students at remote sites.
The Internet success arises from its flexibility. Instead of restricting component networks to a particular manufacturer or particular type, Internet technology allows interconnection of any kind of computer network. No network is too large or too small, too fast or too slow to be interconnected. Thus, the Internet includes inexpensive networks that can only connect a few computers within a single room as well as expensive networks that can span a continent and connect thousands of computers. See Local Area Network.
Internet service providers (ISPs) provide Internet access to customers for a monthly fee. A customer who subscribes to an ISPs service uses the ISPs network to access the Internet. Because ISPs offer their services to the general public, the networks they operate are known as public access networks. In the United States, as in many countries, ISPs are private companies; in countries where telephone service is a government-regulated monopoly, the government often controls ISPs.
An organization that has many computers usually owns and operates a private network, called an intranet, that connects all the computers within the organization. To provide Internet service, the organization connects its intranet to the Internet. Unlike public access networks, intranets are restricted to provide security. Only authorized computers at the organization can connect to the intranet, and the organization restricts communication between the intranet and the global Internet. The restrictions allow computers inside the organization to exchange information but keep the information confidential and protected from outsiders.
The Internet has grown tremendously since its inception, doubling in size every 9 to 14 months. In 1981 only 213 computers were connected to the Internet. By 2000 the number had grown to more than 100 million. The current number of people who use the Internet can only be estimated. One survey found that there were 61 million Internet users worldwide at the end of 1996, 148 million at the end of 1998, and 407 million by the end of 2000. Some analysts estimate that the number of users will double again by the end of 2002.
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