10Base2   The 10Base-2 standard (Thinnet) uses 50 ohm coaxial cable with maximum lengths of 185 meters. This cable is thinner and more flexible than that used for the 10Base-5 standard. Cables in the 10Base-2 system connect with BNC connectors. The Network Interface Card (NIC) in a computer requires a T-connector where you can attach two cables to adjacent computers. Any unused connection must have a 50 ohm terminator.

10baseT   A version of Ethernet in which stations are attached by twisted pair cable, the traditional cables used for telephone lines. 10BaseT uses a star formation, and transmits at 10 megabits per second.

ADAPTER   A part that connects two devices or systems, physically or electrically, and enables them to work together. It can be a plug that allows two wires to be connected, for example, or a printed circuit board that modifies the computer so it can work with certain hardware or software.

ADSL   Asymmetric Digital Subscriber Line, or Asymmetric Digital Subscriber Loop. A digital subscriber line (DSL) technology in which the transmission of data from server to client is much faster than the transmission from client to server. Whereas with HDSL (High-Speed Digital Subscriber Line), transmission is 784 kbp in both directions, with ADSL, the rate from client to server is 640 kilobytes per second and from server to client can be up to 6 megabits per second. This kind of connection is useful with applications such as interactive TV and Video on Demand, because the data the server sends is much more than the data sent by the client. ADSL uses bandwidth that is not used by voice; therefore voice and data can be transmitted at the same time.

API   Abbreviation of application program interface, a set of routines, protocols, and tools for building software applications. A good API makes it easier to develop a program by providing all the building blocks. A programmer puts the blocks together.

ARPANET   Advanced Research Projects Agency Network. A wide area network developed in the 1960s by the Advanced Research Projects Agency of the U.S. Department of Defense, that linked government sites, academic research sites, and industrial sites around the world. Later, the military communications part split off and was named MILNET. ARPANET was the testing ground and original backbone of the Internet.

AT   Advanced Technology. An IBM PC introduced in 1984 that was the most advanced PC at that time, with an Intel 80286 processor, 16-bit bus, and 1.2MB floppy drive.

ATAPI   AT Attachment Packet Interface -- an extension to EIDE that enables the interface to support CD-ROM players and tape drives.

ATX   The modern-day shape and layout of PC motherboards. It improves on the previous standard, the Baby AT form factor, by rotating the orientation of the board 90 degrees. This allows for a more efficient design, with disk drive cable connectors nearer to the drive bays and the CPU closer to the power supply and cooling fan.

AUI   Attachment Unit Interface -- the portion of the Ethernet standard that specifies how a cable is to be connected to an Ethernet card. AUI specifies a coaxial cable connected to a transceiver that plugs into a 15-pin socket on the network interface card (NIC).

AWG   American Wire Gauge.

BAUD RATE   The number of signaling elements that occur each second.

BIOS   Stands for Basic Input/Output System. A set of instructions stored on a ROM chip inside IBM PCs and PC-compatibles, which handles all input-output functions and controls how your PC starts up, and stores information about which devices are attached to it in the CMOS memory.

BIT   Short for binary digit. The smallest unit of information a computer can hold. The value of a bit is 1 or 0. There are 8 bits in a Byte.

BNC   Short form for British Naval Connector or Bayonet Nut Connector or Bayonet Neill Concelman. It is a type of connector used with coaxial cables such as the RG-58 A/U cable used with the 10Base-2 Ethernet system. The basic BNC connector is a male type mounted at each end of a cable. This connector has a center pin connected to the center cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to any female connector.

BNC T   BNC T-connectors are female devices for connecting two cables to a network interface card. A BNC barrel connector allows connecting two cables together.

BUFFER   A reserved area of memory for temporarily holding data. A buffer can hold data being sent from a high-speed device to a low-speed device until the slower device can accept the input; for example, to hold data sent to a printer until the printer is ready for it.

BUS   A set of conductors which connect the functional units in a computer. It is called a bus because it travels to all destinations. There are local busses that connect elements within the CPU and busses which connect the computer to external memory and peripherals. The bus width determines the speed of data transmission. Most personal computers use 32-bit busses both internally and externally. Internal busses are configured in parallel; there are also serial busses between computers in networks.


The standard measurement of storage capacity. A Byte is made up of eight bits, which is pretty much the same as eight characters.

See also KiloByte (KB), MegaByte (MB)and GigaByte (GB), which are approximately a thousand, a million, or a billion Bytes.

The work 'Byte' is capitalized to help distinguish the word from "bits" (e.g. "Kb", "Mb").

CABLE   A flexible wire or bundle of wires, usually metal (glass or silica in fiber optic cable), insulated with plastic or rubber, and having connectors on the ends. Some kinds of cable, especially coaxial cable and fiber optics cable, are used in electronics and computer networking.

CACHE   A temporary storage area for frequently-accessed or recently-accessed data. Having certain data stored in cache speeds up the operation of the computer. There are two kinds of cache: internal (or memory cache) and external (or disk cache). Internal cache is built into the CPU, and external cache is on the motherboard. When an item is called for, the computer first checks the internal cache, then the external cache, and finally the slower main storage. A cache hit (accessing data from a cache) takes much less time than retrieving information from the main memory; the cache has high-speed memory chips. The cache may also be used as a temporary storage area for data that will be written to disk when the computer is idle.

CATEGORY 5  (CAT-5) Category 5 describes network cabling that consists of four twisted pairs of copper wire terminated by RJ45 connectors. Category 5 cabling supports frequencies up to 100 MHz and speeds up to 100 Mbps.

CDROM   Compact Disc Read-Only Memory. An optical disk that is physically the same as an audio CD, but contains computer data. Storage capacity is about 680 megabytes. CD-ROMs are interchangeable between different types of computers.

CENTRONICS   A standard interface for connecting printers and other parallel devices. For PCs, almost all parallel ports conform to the Centronics standard. Two new parallel port standards that are backward compatible with Centronics, but offer faster transmission rates, are ECP (Extend Capabilities Port) and EPP (Enhanced Parallel Port).

CFM   Cubic feet per minute, the measure of air flow, representing how much air is displaced in 1 minute.

CMOS   Complementary Metal Oxide Semiconductor. A kind of integrated circuit used in a bit of memory on your motherboard that contains configuration information about your computer.

COAXIAL CABLE   A cable consisting of a single conductor which is surrounded by insulation and a conductive shield. The shield usually is connected to an electrical ground and prevents the cable from picking up or emitting electrical noise. Coaxial cable is used in communications.

COM PORT   A serial communications port.

CONDUCTOR   A material through which electrical current can flow.

CPU   Central Processing Unit. The CPU controls the operation of a computer. Units within the CPU perform arithmetic and logical operations and decode and execute instructions. In microcomputers, the entire CPU is on a single chip.

CSMA/CD   Carrier Sense, Multiple Access, Collision Detection. Ethernet packets are transmitted using CSMA/CD, which means the sending computer waits for the line to be free before sending a message, then sends; if two computers accidentally transmit at the same time and their messages collide, they wait and send again at different times.

DAISY CHAIN   A type of cabling configuration in which devices are connected along a continuous line.

DDC   Short form for Display Data Channel. It is a VESA standard for communication between a monitor and a video adapter. Using DDC, a monitor can inform the video card about its properties, such as maximum resolution and color depth. The video card can then use this information to ensure that the user is presented with valid options for configuring the display.

DECnet   A network protocol from Digital Equipment Corporation, which can interconnect PDP, VAX, PC, and Macintosh computers.

DEVICE DRIVER   A device driver is a program that extends the operating system to support a device such as a disk or tape drive; or a program that enables an application to use a device such as a printer. Hardware devices such as sound cards, printers, scanners, and CD-ROM drives must each have the proper driver installed in order to run.

DHCP   Dynamic Host Configuration Protocol. Windows NT Server software that assigns an IP address to each node in a network.

DIN   Stands for Deutsche Industrinorm, the standards -setting organization for Germany. A DIN connector is a connector that conforms to one of the many standards defined by DIN. DIN connectors are used in keyboard connectors for PCs.

DMA   Direct Memory Access/Addressing. A method of transferring data from one memory area to another without having to go through the central processing unit.

DNS   Domain Name System. A database system that translates an IP address into a domain name. For example, a numeric address like 232.452.120.54 can become something like xyz.com

DOMAIN NAME   An Internet address in alphabetic form. Domain names must have at least 2 parts: the part on the left which names the organization, and the part on the right which identifies the highest subdomain, such as the country (fr for France, uk for United Kingdom) or the type of organization (com for commercial; edu for educational, etc.). Directory levels can be indicated in other parts. The IP address is translated into the domain name by the domain name server.

DOS   Acronym for disk operating system. The term DOS can refer to any operating system, but it is most often used as a shorthand for MS-DOS (Microsoft disk operating system). Originally developed by Microsoft for IBM, MS-DOS was the standard operating system for IBM-compatible personal computers.

DOT MATRIX PRINTER   The workhorse of the computer industry, the dot matrix printer has been around for years and years. They're very reliable and fast, but the print quality often leaves something to be desired. They work by using a matrix of pins to form the letters, which press through a ribbon to form characters on the paper. One big advantage of dot matrix printers is their ability to easily handle multi-part forms. They're used often at point-of-sale terminals. Many cash registers employ small dot matrix printers.

DPI   Dots per inch is the standard measurement of printer resolution. A printer (unless it's a plotter) lays down a character as a series of dots. It stands to reason that the more dots you can cram into an inch of space, the better your text will look. This is also called resolution.The more dots per inch, the higher the resolution: 600 dpi would mean 600 x 600 = 360,000 dots per square inch

DSL   Digital Subscriber Line or Digital Subscriber Loop. A way of sending digital data over regular copper telephone lines. It is also called High-Speed DSL (HDSL).

ECP   Enhanced Capabilities Port. A high-speed enhanced parallel port from Microsoft.

EEPROM   Electrically Erasable Programmable Read Only Memory. A memory chip that can be recorded or erased electrically, but that does not lose its content when electrical power is removed. It is called ROM even though it can be recorded, because it takes a lot longer to record than RAM and is only practical for recording data which is not changed often.

EIA   Electronics Industries Association. An organization which establishes Recommended Standards (RS) for hardware devices and their interfaces. RS-232 is a well-known standard for transmitting serial data by wire.

EIDE   Enhanced Integrated Drive Electronics. A hardware interface which is faster than IDE, allows more memory, and can connect up to four devices (such as hard drives, tape drives, and CD-ROM drives) to the computer.

EPP   Enhanced Parallel Port. A high-speed transfer parallel port that can support several devices in a daisy chain formation.

ETHERNET   The most popular type of local area network, which sends its communications through radio frequency signals carried by a coaxial cable. Each computer checks to see if another computer is transmitting and waits its turn to transmit. If two computers accidentally transmit at the same time and their messages collide, they wait and send again in turn. Software protocols used by Ethernet systems vary, but include Novell Netware and TCP/IP.

FAN   A cooling device that circulates air in a computer; fans are necessary to keep the computer from overheating.

FCC   Federal Communications Commission. A U.S. government agency that regulates interstate and foreign communications. The FCC sets rates for communications services; determines standards for equipment; and controls broadcast licensing.

FIBER OPTICS(FO)   The transmission of data in the form of pulses of light. Fiber optics uses cables containing glass or silica fibers no thicker than a human hair. There is very little signal loss, and information can be transmitted at high speed over long distances. Fiber optic cables do not have problems with external noise like wire cables do, and are better for transmissions requiring security.

FIFO   First In First Out. A method of storage in which the data stored for the longest time will be retrieved first.

FIREWIRE   The former name for High Performance Serial Bus. A serial bus developed by Apple Computer and Texas Instruments (IEEE 1394). The High Performance Serial Bus can connect up to 63 devices in a tree-like daisy chain configuration, and transmit data at up to 400 megabits per second. It supports plug and play and peer-to-peer communication between peripheral devices.

FLOPPY DRIVE   Today's standard floppy drive is 3.5" and holds 1.44 megabytes of data. Floppies can also come in 5.25" sizes and other capacities. Floppies are the most common portable method of data storage. They can be used to move data from one computer to another, for backup purposes, or for distribution of software. Floppy drives may one day be supplanted by removable drives.

FTP   File Transfer Protocol. A client/server protocol for exchanging files with a host computer. Examples are Xmodem, Ymodem, Zmodem and Kermit.

FULL DUPLEX   A communications channel which transmits data in both directions at once.

HALF DUPLEX   A communications channel which transmits data in either direction, but only one direction at a time.

HARD DRIVE(HDD)   The most common form of permanent data storage for your system, it consists of special magnetically-coated platters designed to store mass quantities of data. New on the market are Ultra DMA hard drives. Ultra DMA hard drives have a faster access time, but require that your motherboard supports this standard. It won't, however, hurt to put a UDMA drive on a system that doesn't support it. It will work like a standard hard drive. And if you should decide to upgrade you motherboard later, you'll have a drive that's ready for it.

HUB   Like the hub of a wheel, a central device that connects several computers together or several networks together. A passive hub may simply forward messages; an active hub, or repeater, amplifies or refreshes the stream of data, which otherwise would deteriorate over a long distance.

HVD   High Voltage Differential, also called Differential. A type of SCSI signal. An HVD SCSI system provides reliable signaling in high noise environments over a long bus length (up to 25m [82ft]). HVD hardware cannot be mixed with other SCSI signal types. A Differential bus requires Differential terminators. Less than 5% of all SCSI hardware uses HVD signaling.

I/O   Input/Output. Transfer of data into a computer, and from the computer to the outside world.

I/O ADDRESS   Input/Output address. A unique address given to a peripheral device for input and output; on a PC, the I/O address is in the form of a three-digit hexademical number.

I/O DEVICE   Input/Output device. A device that is used to transfer data into or out of the computer; also called peripheral device.

ICQ (I SEEK YOU)   A chat program from Mirabilis for Windows 95. It can be set to notify the user when friends are online; it seeks out friends of the user so messages and files can be exchanged.

IDE   Integrated Drive Electronics preceded EIDE on the market. IDE has a slower transfer rate, and will only allow two devices to be connected to the interface at one time.

IEEE   Institute of Electrical and Electronics Engineers. A worldwide professional association for electrical and electronics engineers, which sets standards for telecommunications and computing applications.

INKJET PRINTER   The inkjet printer, as its name implies, makes an image by spraying tiny jets of ink onto the paper. Until recently, the resolution on inkjet printers could not come close to laser printers, but technology has brought resolution up and prices down. For most color work, and inkjet printer is a good investment. Artists may want to look into a color laser or other type of printer. They're higher in cost, but the quality is far superior.

INTERNET   The biggest internet in the world. This worldwide information highway is comprised of thousands of interconnected computer networks, and reaches millions of people in many different countries. The Internet was originally developed for the United States military, and then became used for government, academic and commercial research and communications. The Internet is made up of large backbone networks (such as MILNET, NSFNET, and CREN), and smaller networks that link to them. The U.S. National Science Foundation maintains a major part of the backbone (NSFNET). The Internet functions as a gateway for electronic mail between various networks and online services. The World Wide Web facility on the Internet makes possible almost instantaneous exchange of information by linking documents around the world. Internet computers use the TCP/IP (Transmission Control Protocol/Internet Protocol). There are over six million hosts on the Internet: mainframes, minicomputers or workstations that support the Internet Protocol. The Internet is connected to computer networks worldwide that use various message formats and protocols; gateways convert these formats between networks so that the Internet functions as one big network. UNIX utilities such as FTP, Archie, Telnet, Gopher and Veronica have been widely used to access the Internet. The Internet sometimes appears to be amorphous and unregulated, but there are several administrative bodies: the Internet Architecture Board, which oversees technology and standards; the Internet Assigned Numbers Authority, which assigns numbers for ports and sockets, etc.; InterNIC, which assigns Internet addresses; the Internet Engineering and Planning Group, Internet Engineering Steering Group, and the Internet Society.

INTERRUPT REQUEST LINE(IRQ)   As you may have discovered, it's possible for PC devices to live in the same virtual space, and when they do, they tend to interfere with each other. By setting each device to a different interrrupt request line, either 8 or 16, you can avoid nasty conflicts such as frozen mice or a out-of-control sound cards. Plug-and-Play technology is one step toward eliminating the hassle of setting IRQ's.

INTRANET   A local area network which may not be connected to the Internet, but which has some similar functions. Some organizations set up World Wide Web servers on their own internal networks so employees have access to the organization's Web documents.

IP   Internet Protocol. The IP part of TCP/IP; the protocol that is used to route a data packet from its source to its destination over the Internet.

IPX   Internetwork Packet Exchange. A Novell NetWare protocol for delivering messages in datagram format.

IPX/SPX   Internet Packet Exchange/Sequenced Packet Exchange. IPX is a Novell communications protocol used by NetWare clients and servers to deliver messages within and between networks. SPX ensures reliable delivery of complete messages.

ISA BUS   ISA stands for Industry Standard Architecture, and it was the original 8-bit bus for IBM and compatible computers. Now the ISA bus is 16-bits. Many peripheral cards still conform to ISA standards, though many are moving to PCI.

ISDN   Stands for Integrated Services Digital Network. An ISDN line can deliver speeds of up to 128 kbps. ISDN requires installation of a digital line to the home or office and an ISDN adapter in the computer.

ISO   International Organization for Standardization. A voluntary organization founded in 1946, comprised of the national standards organizations of many countries, and responsible for creating international standards in many areas, including computers and communications. ANSI (American National Standards Institute) is the American member of ISO. ISO produced OSI (Open Systems Interconnection), a seven-layer model for network architecture.

JACK   A connector into which a plug is inserted.

Kbps   Kilobits per second. Modem speed is generally measured in Kbps (kbps), or Mbps (mbps; megabits per second).

KEYBOARD   One of the primary peripherals on your system, and one that is likely to wear out long before the rest of your system ever will. The keyboard, along with the mouse, are the primary means of working with your system. If you have Windows 95/98 or NT, you'll want a 104-key keyboard which has access to the Start button and some menu features directly from your keyboard. Shop around for the keyboard that "feels" best. Some have a louder "click" than others, for example. Others, such as the Microsoft Natural Keyboard," are ergonomically designed. Some keyboards may include a built-in pointing device, most all include a 10-key numeric keypad.

KiloBytes (KB)   One KiloByte (KB) is equal to 1,024 Bytes (approximately 1 thousand Bytes).
One KiloByte also equals 8.192 kilobits (Kb) (8,192 bits).

KVM   Stands for Keyboard-Video-Mouse

LAN   Local Area Network. A network that connects computers that are close to each other, usually in the same building, linked by a cable.

LASER PRINTER   A laser printer works on the same principal as a copier, but instead of scanning an image on a glass platen, the image is fed from the PC to the drum of the printer. Laser printers are faster - and usually cost more - than inkjet or dot matrix printers. The quality, especially for printed text, is generally better, but inkjet technology is catching up.

LED   Light-Emitting Diode. A type of semiconductor diode that emits visible or infrared light when current passes through it. Visible LEDs are used as indicator lights; for example, the light that shows a computer or printer is turned on. Infrared LEDs are used in remote-control devices.

LINUX   Pronounced lee-nucks, A freely-distributable implementation of UNIX that runs on a number of hardware platforms, including Intel and Motorola microprocessors. It was developed mainly by Linus Torvalds. Because it's free, and because it runs on many platforms, including PCs, Macintoshes and Amigas, Linux has become extremely popular over the last couple years.

LOCAL BUS   An extra bus in addition to the main bus in a computer, which provides a fast data path connecting the CPU with memory and peripherals. The local bus is designed to run at the speed of the CPU. The most common local busses are VLB (VESA Local Bus) and PCI (Peripheral Component Interconnect).

LPT   Line Print Terminal. On a personal computer, the usual designation for a parallel port connection to a printer or other device such as a scanner or camera. LPT connections are numbered LPT1, LPT2, LPT3, etc.; most computers have at least one. More parallel ports can be added by installing parallel port adapter cards.

LVD   Low Voltage Differential. A type of SCSI signal growing increasing popular. A typical multimode LVD/SE SCSI system provides a moderately long bus length (up to 12m [39ft]) and downward compatibility with Single Ended hardware. LVD-rated equipment is required for "Ultra" SCSI standards.

Mbps   Megabits per second. Modem speed is generally measured in Mbps or Kpbs (kilobits per second).

MEGABYTE (MB)   One MegaByte is equal to 1,048,5761 Bytes (approximately 1 million Bytes).

MEMORY   Also called main memory. The working space used by the computer to hold the program that is currently running, along with the data it needs, and to run programs and process data. The main memory is built from RAM chips. The amount of memory available determines the size of programs that can be run, and whether more than one program can be run at once. Main memory is temporary, and is lost when the computer is turned off. It is distinguished from more permanent internal memory (ROM) which contains the computer's essential programs, and storage (the disks and tapes which are used to store data).

Mhz   (MegaHertz or megahertz). Millions of cycles per second. The unit of frequency used to measure the clock speed of a computer.

MODEM   It stands for MOdulate, DEModulate. A modem takes digital data and changes (modulates) it to a series of beeps that can travel down and ordinary phone line. It also takes those beeps and changes (demodulates) it back to digital data your computer can understand. Other features you might find on a modem are the ability to send and receive faxes, a speakerphone, and voice mail. Some modems can send data and handle a voice call simultaneously, but that requires a compatible modem on each end of the connection. So what kind do you buy? 28.8? 33.6? 56K? ISDN? You can go up to 56K with a standard telephone line. Actually, the present limit is 53K due to the restrictions the FCC has put on the amount of power that can be applied to a standard telephone line. ISDN requires a special line, and an ISDN modem on the other end as well. 56K modems are the best way to go for most people. One caveat: There are presently at least three competing standards for 56K. Check with your Internet Service Provider and see which, if any standard they offer or intend to offer in the future before you purchase a modem.

MONITOR   Also called a display. A device that displays text and graphics generated by a computer. Desktop monitors are usually cathode-ray tubes, and laptop monitors are usually liquid crystal display. A monitor can be monochrome (black and white) or color. Color monitors may show either digital or analog color. The resolution of a monitor is expressed in dot pitch. The lower the number, the closer the dots are together, which means a finer "grain" picture. Monitors also come in various screen sizes, and like a television, are measured diagonally.

MOTHERBOARD   The main circuit board inside a computer, which contains the central processing unit, the bus, memory sockets, expansion slots, and other components. Additional boards, called daughter boards, can be plugged into the motherboard.

MOUSE   A pointing device that is used to move a cursor on the computer screen, and make various operations possible such as typing, drawing, editing text and graphics, opening and closing files, and giving other commands. The wire connecting it to the computer or keyboard looks like a mouse's tail. A mouse is moved over a flat horizontal surface, usually a rubber mouse pad, and its position is read by the computer. The original mouse has a button which the user clicks or holds down to place the cursor; now many models have more than one button.

NARROW SCSI   A Narrow SCSI bus is capable of transferring 8-bits of information simultaneously. Most external SCSI devices still use Narrow SCSI interfaces, which require 50-pin connections. Some Narrow SCSI connectors have less than 50-pins, which is accomplished by tying ground wires together.

NDIS   Network Device Interface Specification, a Windows device driver interface that enables a single network interface card (NIC) to support multiple network protocols. For example, with NDIS a single NIC can support both TCP/IP and IPX connections. NDIS can also be used by some ISDN adapters.

NETWORK   A means of hooking a number of computers together in order to share data and/or peripherals. A network can have as few as two computers, or practically an infinite number. A perfect example of a very large network is the Internet. When adding a network card to your PC, you need to know to which type of network you'll be connecting. The two most common kinds are thin wire, which uses a BNC connector (it looks sort of like a barrel) and 10BaseT, which uses a connector that looks like a telephone plug on steroids. These days many network cards can accept both kinds of connectors. Networks aren't just for large corporations. Any home with two PC's can network them together inexpensively for sharing files or playing games.

NETWORK INTERFACE CARD (NIC)   an expansion board you insert into a computer so the computer can be connected to a network.

NOISE   An outside signal that interferes with a communications transmission. It can come from heavy machinery, power line spikes, nearby TVs or radios, etc.

ODI   Open Data-link Interface, an application programming interface (API) developed by Novell for writing network drivers. ODI separates the physical network layer (the Data-Link Layer in the OSI model) from the network protocol layer (the Transport Layer). As a result, the same network interface card (NIC) can be used to carry data for different protocols. For example, ODI allows a computer with just one NIC to be simultaneously connected to both an IPX/SPX network and a TCP/IP network.

Ohm   A unit of electrical resistance; the resistance of a conductor in which a potential difference of one volt produces a current of one ampere. Named after Georg Simon Ohm, German physicist (1787-1854).

OPERATING SYSTEM (OS)   The operating system on your computer largely determines the type of software you will be able to use. The most current OS for Macintosh is System 8.x. On the PC side, the most common operating systems are MS-DOS, Windows 3.x, Windows 95/98, Windows NT, UNIX and OS/2. The operating system defines the way you (and your software) interact with the computer. MS-DOS and some versions of UNIX provide a text-only environment where the user has to remember a number of commands. The other operating systems are graphical, so all the user needs to do is point and click using a mouse to start programs or execute other commands. Programs generally have to be written specifically for an operating system. In other words, your favorite Mac game won't run on your PC unless the CD also contains a PC version of the game. Some programs are written specifically for certain versions of operating systems, so when purchasing software check to be sure your operating system and version is compatible with the product.

OS/2   An operating system for PCs developed originally by Microsoft Corporation and IBM, but sold and managed solely by IBM. OS/2 is compatible with DOS and Windows, which means that it can run all DOS and Windows programs. However, programs written specifically to run under OS/2 will not run under DOS or Windows.

PACKET   A unit of data formatted for transmission on a network. Data is broken up into packets for sending over a packet switching network. Each packet has a header containing its source and destination, a block of data content, and an error-checking code. All the data packets related to a message may not take the same route to get to their destination; they are reassembled once they have arrived.

PARALLEL PORT   Normally devices such as printers or external devices such as a Zip Drive or Snappy! Video Capture are hooked up to a parallel port. A parallel port allows for several bits of data to be moved at the same time along different lines. Side by side. For example, a parallel interface can transmit eight bits (a whole byte) at one time, over eight parallel lines. A serial interface transmits only one bit at a time.

PC CARD   The little credit card-size slot on notebook computers and many PDA's and HPC's accepts PC Cards. PC Cards are built to fulfill a variety of functions from networking and modems to sound cards and CD-ROM interfaces. PC Cards also provide an easy way to add additional memory to a portable system. They're also known as PCMCIA cards.

PCI   Peripheral Component Interconnect. A personal computer local bus designed by Intel, which runs at 33 MHz and supports Plug and Play. It provides a high-speed connection with peripherals and allows connection of seven peripheral devices. It is mostly used with Pentium computers but is processor independent and therefore able to work with other processors. It plugs into a PCI slot on the motherboard and can be used along with an ISA or EISA bus.

PCMCIA   Personal Computer Memory Card International Association -- A Sunnyvale, California nonprofit trade association, created to standardize the connection of peripherals to portable computers. The PCMCIA developed the PC Card (often called the PCMCIA card), a lightweight, removable module about the size of a credit card that adds features to a portable computer.

PENTIUM   An Intel high-performance microprocessor introduced in 1993, also called P5, 586, or 80586. The name Pentium refers to the fact that it is the fifth microprocessor in the 80x86 series. It is about twice as fast as the 486.

PERIPHERAL   Any piece of hardware connected to a computer; any part of the computer outside the CPU and working memory. Some examples of peripherals are keyboards, mice, monitors, printers, scanners, disk and tape drives, microphones, speakers, joysticks, plotters, and cameras.

PLUG-AND-PLAY (PnP)   The ability of a computer to automatically detect and configure new hardware components when they are plugged in, without requiring the user to go through complicated installation procedures. With plug and play, it should be possible to immediately use a new peripheral as soon as it is plugged in. Macintosh equipment has always been plug and play; PC users have it since Windows 95. A computer must have a plug and play BIOS on the motherboard as well as the right operating system for plug and play. Expansion boards are designed specifically for plug and play, though if an older expansion board is added, the plug and play system will help the user find the correct settings for it.

POP   Post Office Protocol. A protocol used by mail clients to download messages from a mail server on the Internet.

PORT   Basically it's a place where you plug in a device, be it parallel, serial, IDE, SCSI, etc.

POWER SUPPLY   The power supply takes the current from your wall electrical socket and coverts it into the various voltages your computer needs. The size of a power supply is measured in watts, and a general rule of thumb is the more peripherals the more powerful the supply. Generally speaking, however, a 200 watt power supply will work for most systems. The fan is a great collector of dust, so it's a good idea to blow it out with canned air every once in a while, just to keep the air flowing.

PRINTER   A printer prints data. Common printers are inkjet, laser and Dot Matrix.

PROCESSOR   This is the "brains" of your system. Also called the Central Processing Unit or CPU, the processor handles almost all of the calculations your programs require to run. It goes without saying that the faster CPU speed, the faster it can handle calculations and the faster your program will run. If you're buying a PC, look into a Pentium® III, Celeron processor or other multimedia processor. These processors are designed to better process video and sound, and along they way they'll even calculate your spreadsheet a bit faster. On the Mac side, look for a PowerPC® processor. With the right software, you can run both Mac and PC applications.

PROM   Programmable Read Only Memory. A memory chip that can only be programmed once. Unlike ROM, which is programmed by the manufacturer, PROM is programmed by the user. c.f. EPROM

PS/2   A port type developed by IBM for the purpose of connecting a keyboard or mouse to a PC. The PS/2 port has a mini DIN plug containing 6 pins. PS/2 ports are used so that the serial port can be used by another device. The PS/2 port is often called the mouse port.

RAM   Random Access Memory. The working memory of the computer. RAM is the memory used for storing data temporarily while working on it, running application programs, etc. "Random access" refers to the fact that any area of RAM can be accessed directly and immediately, in contrast to other media such as a magnetic tape where the tape must be wound to the point where the data is. RAM is called volatile memory; information in RAM will disappear if the power is switched off before it is saved to disk. There is also a form of non-volatile RAM, which must be continually energized by a battery to maintain its content. The most common form of RAM is built from semiconductor integrated circuits.

REMOVABLE DRIVE   Be it Zip, Jaz, Syquest, Orb or another brand, a removable drive lets you store more far more data than a floppy, but considerably less than a hard drive. These are popular for backup devices, extra storage on systems, or for transporting files between two systems. Be aware that no two different types of drive cartridges are compatible, so if you need to move data between home and office or between your desktop workstation and a service bureau, make sure both systems have the same brand and type of drive. For example, Iomega makes both the Zip and Jaz drives, but they're physically incompatible. Removable drives are available in both internal and external versions.

REPEATER   A device that amplifies or refreshes a stream of data transmitted over a network, so it can travel to more remote computers. Without repeaters, a transmission will deteriorate as it travels farther and farther from the source.

RESOLUTION   In both printers and monitors, it means how many dots are placed in a certain amount of space. The more dots, the better. In a printer, it's expressed in DPI, or dots per inch, and higher numbers mean better resolution. Monitor resolution is generally expressed in dot pitch, and lower numbers mean better resolution. So a 720 DPI printer will have better output than a 300 DPI model, and a .28 dot pitch screen will look better than a .32

RJ-45   Registered Jack-45, an eight-wire connector used to connect computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors look similar to the RJ-11 connectors used for connecting telephone equipment, but they are a bit wider.

RJ45   Registered Jack-45, an eight-wire connector used to connect computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors look similar to the RJ-11 connectors used for connecting telephone equipment, but they are a bit wider.

ROM   Read-Only Memory. Memory that can be read but not changed. Read-only memory is non-volatile storage; it holds its contents even when the power is turned off. Data is placed in ROM only once, and stays there permanently. ROM chips are used for storage of the essential software of the computer, called firmware. Some kinds of ROM are PROM, EPROM, EEPROM, and CD-ROM.

ROUTER   A device that finds the best path for a data packet to be sent from one network to another. A router stores and forwards electronic messages between networks, first determining all possible paths to the destination address and then picking the most expedient route, based on the traffic load and the number of hops. A router works at the network layer (layer 3 of the OSI model); a bridge works at the data link layer (layer 2). A router does more processing than a bridge does. A router can be hardware or a combination of hardware and software.

RPM   Revolutions Per Minute. The speed at which a disk drive rotates is measured in revolutions per minute.

RS-232   (Recommended Standard-232). An Electronics Industries Association standard asynchronous serial line which is used commonly for modems, computer terminals, and serial printers. RS-232 uses a 25-pin or 9-pin connector. The standard designates the purpose for each of the 25 or 9 lines, including lines for sending and receiving data, ground connections, and control lines. However, often not all of the lines are used. Some connections use only three: one for data in each direction, and one for a ground. Data sent over RS-232 is a stream of bits at a constant speed. Each character is preceded by a start bit and followed by one or two stop bits; a positive voltage is transmitted for a 0 bit, a negative voltage for a 1. RS-232 is normally used for short distances; the maximum distance with high-quality cable would be several hundred feet. The standard is now officially called EIA-232D, but RS-232 is the name in common use.

SCANNER   An input device that reads images or text and converts the data into digital signals. Graphical scanners read photos or other images into the computer and digitize them, producing bitmapped graphics files. Text scanners use optical character recognition software to read pages of text and produce editable text files. Bar code scanners, as used in stores, convert bar codes into digital information. Some types of scanners are flatbed scanners, sheet-fed scanners, hand-held scanners, and slide scanners.

SCSI   Pronounced, "scuzzy" it provides a way of chaining a number of devices together. SCSI stands for Small Computer System Interface. While SCSI is standard on a Macintosh, a PC requires an interface card in order to use SCSI devices. Common SCSI devices include hard drives, CD-ROM drives, scanners and removable drives. Many of these devices are also available in other in other interfaces (hard drives and CD-ROMs in the PC world commonly use EIDE interfaces), so having one such device hooked into your PC does not necessarily mean you have a SCSI adapter.

SCSI ID   A unique address assigned to a SCSI device. Narrrow SCSI devices must have an ID between 0-7. Wide SCSI devices can have an ID between 0-15.

SERIAL PORT   Devices such as mice and modems are hooked into a serial port. Serial data is moved one bit at a time, one after another.

SINGLE ENDED   The most common type of SCSI signal. Most SCSI devices use "normal" SE signaling, which limits the maximum length of a SCSI bus to 1.5m (4.9ft). This includes most 50-pin (Narrow) SCSI devices such as scanners and Zip drives.

SMTP   Simple Mail Transfer Protocol. A server-to-server protocol for delivering electronic mail. The standard protocol used on the Internet; also used on other TCP/IP networks.

SOCKET 7   The socket where the CPU is connected to the motherboard, on 486 and Pentium systems.

SOUND CARD   An add-on expansion board that improves a computer's sound quality, and adds other sound capabilities. A sound card makes it possible to use speakers, a stereo, and a microphone to record and play sound; some sound cards also include MIDI.

SPEAKERS   If your system has a sound card, it needs a pair of speakers. A pair of headphones will work just fine, or if your card has a LINE OUT jack (and most do) you can connect it to a home stereo system. Multimedia speakers have a built-in amplifier so you can hear the music and control the volume without need of a rack of stereo equipment.

SPX   Sequenced Packet Exchange. A Novell NetWare communications protocol used to transmit messages reliably over a network.

SRAM   Static Random Access Memory. A kind of random access memory that requires a constant supply of power in order to hold its content, but does not require refresh circuitry as dynamic random access memory (DRAM) does. Each static RAM bit is a flip-flop circuit made of cross-coupled inverters; the activation of transistors controls the flow of current from one side to the other. Unlike read-only memory (ROM), SRAM will lose its content when the power is switched off. Static RAM is usually faster than dynamic RAM, but takes up more space and uses more power. It is used for the parts of a computer that require highest speed, such as cache memory.

STP   Shielded Twisted Pair. Twisted pair cable that is wrapped in a metal sheath to provide extra protection from external interfering signals.

SURGE   A sudden pulse of extra voltage, lasting a second or longer, which can cause the computer to crash and damage files or computer components if there is no surge protector on the line. A burst of extra voltage that lasts only a fraction of a second is called a spike.

SVGA   Super VGA, a set of graphics standards designed to offer greater resolution than VGA. There are several varieties of SVGA, each providing a different resolution.

TCP   Transmission Control Protocol. The most common Internet transport layer protocol, defined in STD 7, RFC 793. This communications protocol is used in networks that follow U.S. Department of Defense standards. It is based on the Internet Protocol as its underlying protocol; TCP/IP means Transmission Control Protocol over Internet Protocol. TCP is connection-oriented and stream-oriented, and provides for reliable communication over packet-switched networks.

TCP/IP   The Transmission Control Protocol (TCP) on top of the Internet Protocol (IP). These protocols were developed by DARPA to enable communication between different types of computers and computer networks. The Internet Protocol is a connectionless protocol which provides packet routing. TCP is connection-oriented and provides reliable communication and multiplexing.

TELNET (TN)   A terminal emulation protocol that lets a user log in remotely to other computers on the Internet; it has a command line interface. Originally developed for ARPAnet, Telnet runs on top of the TCP/IP protocol.

TERMINATOR   A small device designed to dampen electrical signals reflected from the ends of a SCSI cable. Termination is disabled for any SCSI device that is positioned between the two cable ends.

TRACKBALL   This is a popular alternative to a mouse. The beauty of this is that you can keep your arm pretty much in one spot. They're also very handy for some types of games, and popular on laptops because they're compact.

TRANSCEIVER   Transmitter-receiver. A device that transmits and receives data.

UART   Pronounced u-art, and is a short form for universal asynchronous receiver-transmitter. The UART is a computer component that handles asynchronous serial communication. Every computer contains a UART to manage the serial ports, and all internal modems have their own UART.

UDP   User Datagram Protocol. A communications protocol for the Internet network layer, transport layer, and session layer, which makes it possible to send a datagram message from one computer to an application running in another computer. Like TCP (Transmission Control Protocol), UDP is used with IP (the Internet Protocol). Unlike TCP, UDP is connectionless and does not guarantee reliable communication; the application itself must process any errors and check for reliable delivery.

UNIDIRECTIONAL   In only one direction; referring to a data channel that only transmits one way.

UNINTERRUPTIBLE POWER SUPPLY (UPS)   A UPS will provide battery backup for your system to keep it running in case of a power failure. A basic UPS unit will keep your computer running for a few minutes, while the more powerful ones will keep your system running for hours. Even a basic UPS will keep your PC running during a momentary power loss, and will give you time to save your data and safely power your system down in the case of a power failure.

UNIVERSAL SERIAL BUS   This standard is supported under Windows 98, the iMac, and some Maciintosh G3 systems. USB allows for connection of up to 127 devices to your PC. These devices include, but are certainly not limited to, mice, keyboards, monitors, joysticks and handheld scanners as well as a number of exciting new devices being developed.

UNIX   Pronounced yoo-niks, a popular multi-user, multitasking operating system developed at Bell Labs in the early 1970s. Created by just a handful of programmers, UNIX was designed to be a small, flexible system used exclusively by programmers. Although it has matured considerably over the years, UNIX still betrays its origins by its cryptic command names and its general lack of user-friendliness.

UTP   Unshielded Twisted Pair. The cable used for most telephone wire, and is also used for some computer-to-computer communications. It contains pairs of unshielded wires twisted together, and is a cheap and fairly noise-free way to transmit signals. In shielded twisted pair cables, each pair has a metal sheath around it for protection against interference. Unshielded twisted pair lacks the sheath, but has the advantage of being more flexible and thinner.

VESA   Video Electronics Standards Association. An organization which sets standards for video and multimedia in PCs. VESA established the Super VGA (SVGA) standard and the VESA Local Bus. VESA is headquartered in San Jose, California, and its members are PC vendors.

VGA   Video Graphics Array. A video display standard for color monitors that superseded CGA and EGA. VGA monitors display 16 colors at a resolution of 640 x 480 pixels, the minimum standard display. The vertical scan frequency is around 56Hz to 60Hz. For multimedia applications, it is better to have Super VGA.

VIDEO CARD   Also called graphics adapter, display adapter, video adapter. A circuit board that enables a computer to display information on its screen. The resolution, number of colours, and refresh rate of a monitor is determined by the kind of video card used, plus the limitations of the monitor itself.

VIEWABLE IMAGE SIZE   Along with a monitor's screen size a Viewable Image Size is listed. This number is measured diagonally, just like a monitor or television screen. While your monitor may have a 15" screen, the actual area reserved for the picture may measure 14.5"

VL-BUS   The VESA local bus is many times faster than ISA, but it seems to be going by the wayside. But just like the man in Monty Python's plague village, it's not dead, yet. You'll find the VL-Bus mainly on 386 and 486 machines. If you decide to upgrade to a Pentium® motherboard, you'll have to swap out your old VL-Bus cards for PCI and ISA cards.

WAN   wide area network. A network in which computers are connected to each other over a long distance, using telephone lines and satellite communications. See local area network (LAN).

WIDE SCSI   A Wide SCSI bus is capable of transferring 16-bits of information simultaneously -- twice as much as a Narrow SCSI bus. At present, most internal SCSI drives use Wide SCSI interfaces, which require 68-pin or 68-contact connectors.

XEON   A new Pentium II cartridge introduced by Intel in 1998, designed for use with high performance servers. The Xeon, twice as tall as the Pentium II, fits into new connector called Slot Two. Other improvements are new type L2 cache CSRAM chips, which run at full CPU speed; support for clustered servers; new chip sets 82440GX and 82450NX; possibility of caching up to 8 GB RAM; ability to use up to eight Xeons in one server.

XGA   Extended graphics array, a high-resolution graphics standard introduced by IBM. It provides resolutions of 640 by 480 or 1024 by 768 pixels, and supports simultaneous colors (65 thousand colors). In addition, XGA allows monitors to be non-interlaced