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PC Webopedia is the only online dictionary and search engine you need for computer and Internet technology definitions.

Webopedia is a free online dictionary for words, phrases and abbreviations related to computer and Internet technology.

Webopedia provides easy-to-understand definitions in plain language, avoiding heavy jargon when possible so that the site is accessible to users with a wide range of computer knowledge.

Full-time, experienced editors gather information from standards bodies, leading technology companies, universities, professional online technical publications, white papers and professionals working in the field. The sources used are often listed in the links below the definition if the sources can provide more information than was included in the definition. Every definition is verified among multiple sources; definitions are never based on just one source.

The definitions on Webopedia evolve and change as technologies change, so the definitions are frequently updated to reflect trends in the field. New terms are added daily, and many of the new terms come from suggestions from the site’s users.

In addition to a definition of the term or phrase, Webopedia also provides links to sources of further information on the topic where applicable.


A buzzword for both hardware and software that are designed primarily around the end-user experience and user interface rather than focusing on the task that the product is meant to accomplish. The design of humanware often begins with understanding the needs and limitations of the end user and working backwards to design the final product. Typically, a great deal of testing is done on the product to ensure that its design is enhancing the end user’s experience in the desired way. For example, technology designed to aid persons with disabilities typically begins with understanding the end user’s needs before designing the product.

end user

The final or ultimate user of a computer system. The end user is the individual who uses the product after it has been fully developed and marketed. The term is useful because it distinguishes two classes of users, users who require a bug -free and finished product (end users), and users who may use the same product for development purposes. The term end user usually implies an individual with a relatively low level of computer expertise. Unless you are a programmer or engineer, you are almost certainly an end user.


Short for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps. A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. USB also supports Plug-and-Play installation and hot plugging.

Starting in 1996, a few computer manufacturers started including USB support in their new machines. It wasn’t until the release of the best-selling iMac in 1998 that USB became widespread. It is expected to replace serial and parallel ports completely.

Also see USB 2.0.


Computer instructions or data. Anything that can be stored electronically is software. The storage devices and display devices are hardware. The terms software and hardware are used as both nouns and adjectives. For example, you can say: “The problem lies in the software,” meaning that there is a problem with the program or data, not with the computer itself. You can also say: “It’s a software problem.” The distinction between software and hardware is sometimes confusing because they are integrally linked. When you purchase a program, you are buying software.

But to buy the software, you need to buy the disk (hardware) on which the software is recorded. Software is often divided into two categories: systems software: Which includes the operating system and all the utilities that enable the computer to function. applications software: Includes programs that do real work for users. For example, word processors, spreadsheets, and database management systems fall under applications software.


Refers to objects that you can actually touch, like disks, disk drives, display screens, keyboards, printers, boards, and chips. In contrast, software is untouchable. Software exists as ideas, concepts, and symbols, but it has no substance. Books provide a useful analogy. The pages and the ink are the hardware, while the words, sentences, paragraphs, and the overall meaning are the software. A computer without software is like a book full of blank pages — you need software to make the computer useful just as you need words to make a book meaningful.


A boundary across which two independent systems meet and act on or communicate with each other. In computer technology, there are several types of interfaces. user interface – the keyboard, mouse, and menus of a computer system. The user interface allows the user to communicate with the operating system. Also, see GUI.

Software interface – the languages and codes the applications use to communicate with each other and the hardware.hardware interface – the wires, plugs and sockets that hardware devices use to communicate with each other.(v.) To connect with or interact with using an interface.

graphical user interface

Abbreviated GUI (pronounced GOO-ee). A program interface that takes advantage of the computer’s graphics capabilities to make the program easier to use. Well-designed graphical user interfaces can free the user from learning complex command languages. On the other hand, many users find that they work more effectively with a command-driven interface, especially if they already know the command language.
Graphical user interfaces, such as Microsoft Windows and the one used by the Apple Macintosh, feature the following basic components:

pointer: A symbol that appears on the display screen and that you move to select objects and commands. Usually, the pointer appears as a small angled arrow. Text -processing applications, however, use an I-beam pointer that is shaped like a capital I.

pointing device: A device, such as a mouse or trackball, that enables you to select objects on the displayscreen.

icons : Small pictures that represent commands, files, or windows. You can execute a command or convert the icon into a window by moving the pointer to the icon and pressing a mouse button. You can also move the icons around the display screen as if they were real objects on your desk.

desktop : The area on the display screen where icons are grouped is often referred to as the desktop because the icons are intended to represent real objects on a real desktop.

Windows: You can divide the screen into different areas. You can run a different program in each window or display a different file. You can move windows around the display screen and change their shape and size at will.

menus: Most graphical user interfaces let you execute commands by selecting a choice from a menu.
The first graphical user interface was designed by Xerox Corporation’s Palo Alto Research Center in the 1970s, but it was not until the 1980s and the emergence of the Apple Macintosh that graphical user interfaces became popular. One reason for their slow acceptance was the fact that they require considerable CPU power and a high-quality monitor, which until recently were prohibitively expensive.

In addition to their visual components, graphical user interfaces also make it easier to move data from one application to another. A true GUI includes standard formats for representing text and graphics. Because the formats are well-defined, different programs that run under a common GUI can share data. This makes it possible, for example, to copy a graph created by a spreadsheet program into a document created by a word processor.

Many DOS programs include some features of GUIs, such as menus, but are not graphics based. Such interfaces are sometimes called graphical character-based user interfaces to distinguish them from true GUIs.

USB 2.0

Also referred to as Hi-Speed USB, USB 2.0 is an external bus that supports data rates up to 480Mbps. USB 2.0 is an extension of USB 1.1. USB 2.0 is fully compatible with USB 1.1 and uses the same cables and connectors. Hewlett-Packard, Intel, Lucent, Microsoft, NEC and Philips jointly led the initiative to develop a higher data transfer rate than the 1.1 specification to meet the bandwidth demands of developing technologies. The USB 2.0 specification was released in April 2000.

peripheral device

A computer device, such as a CD-ROM drive or printer, that is not part of the essential computer, i.e., the memory and microprocessor. Peripheral devices can be external — such as a mouse, keyboard, printer, monitor, external Zip drive or scanner — or internal, such as a CD-ROM drive, CD-R drive or internal modem. Internal peripheral devices are often referred to as integrated peripherals. Also see I/O.


Short for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in analogue waves. A modem converts between these two forms.

Fortunately, there is one standard interface for connecting external modems to computers called RS-232. Consequently, any external modem can be attached to any computer with an RS-232 port, which almost all personal computers have. Some modems are an expansion board that you can insert into a vacant expansion slot. These are sometimes called onboard or internal modems.

While the modem interfaces are standardized, several different protocols for formatting data to be transmitted over telephone lines exist. Some, like CCITT V.34, are official standards, while private companies have developed others. Most modems have built-in support for the more common protocols — at slow data transmission speeds, most modems can communicate with each other. At high transmission speeds, however, the protocols are less standardized.

Aside from the transmission protocols that they support, the following characteristics distinguish one modem from another:

bps: How fast the modem can transmit and receive data. At slow rates, modems are measured in terms of baud rates. The slowest rate is 300 baud (about 25 cps). At higher speeds, modems are measured in bits per second (bps). The fastest modems run at 57,600 bps, although they can achieve even higher data transfer rates by compressing the data. Obviously, the faster the transmission rate, the faster you can send and receive data. Note, however, that you cannot receive data any faster than it is being sent. If, for example, the device sending data to your computer is sending it at 2,400 bps, you must receive it at 2,400 bps. It does not always pay, therefore, to have a high-speed modem. In addition, some telephone lines cannot transmit data reliably at very high rates.

voice/data: Many modems support changing voice and data modes. In data mode, the modem acts like a regular modem. In voice mode, the modem acts like a regular telephone. Modems that support a voice/data switch have a built-in loudspeaker and microphone for voice communication.

auto-answer: An auto-answer modem enables your computer to receive calls in your absence. This is only necessary if you offer some computer service people can call in to use.
data compression: Some modems perform data compression, enabling them to send data faster. However, the modem at the receiving end must be able to decompress the data using the same compression technique.

flash memory: Some modems come with flash memory rather than conventional ROM, so the communications protocols can be easily updated if necessary.

Fax capability: Most modern modems are fax modems that can send and receive faxes.

To get the most out of a modem, you should have a communications software package, a program that simplifies transferring data.

Also, see Dial-Up Modem Standards in the Quick Reference section of Webopedia.


Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.

Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

There are several different types of memory:

RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.

ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to.

PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.

EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light.

EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.


A silicon chip that contains a CPU. The terms microprocessor and CPU are used interchangeably in the world of personal computers. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.

Three basic characteristics differentiate microprocessors:

  • Instruction set: The set of instructions that the microprocessor can execute.
  • bandwidth: The number of bits processed in a single instruction.
  • clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
  • In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.

In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).

See the Microprocessor Comparison Chart page in the Quick Reference section of Webopedia for a comparison of microprocessors.

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