- A set of wires used to send an address to the memory; the memory uses this address to decide which data item (i.e. which memory location) is to be read (and sent to the processor) or written (copied from the processor); the memory send or receives the data for the memory via the data bus.
- (Asymmetric Digital Subscriber Line) A WAN connection for higher-speed connections between networks. Used over telephone wiring, often to connect home PCs to the Internet.
- (Advanced Graphics Processor, or Accelerated Graphics Port) A connection for higher-speed graphics cards, faster that PCI slots. Usually as a slot for an AGP Expansion Card, but maybe on board. Gives transfer rates of 266Mbps up to 1Gbit per second. AGP slots & cards use a dual-row edge connector.
- (Audio/Modem Riser) an Intel specification, packaging the analog I/O audio functions of modem circuitry together with a codec chip on a small board, plugging onto a motherboard.
- Operating using continuously variable quantities- such as voltages, which may take on any value, not just discrete quantized levels. As opposed to Digital.
- A single, binary digit, capable of representing one of only two values - which might be true/false, on/off, black/white, 0/1, or any other two-valued item. See also binary number lecture notes.
- A disk you can start the computer up from; a floppy disk or CD can allow you to start up a computer whose operating system is faulty, to fix problems or load a new OS.
- abbreviation for Bits per Second. A measure of data transfer speed, used in networking, e.g. for modem speed. Usually as kilobits per second (kbps - 1000 bits per second) and Megabits per second (Mbps - million bits per second); see Metric Prefixes.
- A high-speed type of memory between the processor and the main memory, used to speed up access to main memory. In a PC, there are two kinds: the Level-1 is on the processor, Level-2 is on the Motherboard
- A connector for the parallel interface found on many computers for connecting printers (etc), named after the printer manufacturer that invented the interface, although Epson further developed the PC version. [Picture]
- In a computer, the signal that controls the speed of the processor (or graphics card, sound card etc); the clock speed of the computer is measured in MegaHertz or GigaHertz. See also real-time clock.
- (Complementary Metal-Oxide Semiconductor) - memory that is kept alive (i.e. made non-volatile by the motherboard battery, to run the real-time clock and remember the BIOS settings.
- Cyan, Magenta, Yellow, Black; colours used in colour printing inks to make all colours, and representing colours on the computer using these colours; compare with RGB.
- (COder/DECoder or COmpressor/DECompressor) either a chip or some software used for encoding & decoding digital sound or video. May be part of the Analog-Digital conversion, or just for coding/compressing data for transmission/reception
- a sudden computer failure; usually through a software fault. A "system crash" causes the whole machine to stop working; a "program crash" may just cause a program to stop, leaving the computer running otherwise.
- A radial division of data on a disk drive, where the head stays at the same radius around the whole of all of the surfaces - that is, a cylinder is all the tracks, on all the surfaces, at the same radius. See track, sector and block.
- (Double Data Rate) - A form of memory where the reading and writing can occur on both edges of the FSBclock, making the memory up to twice as fast. {also Dial-on-Demand Routing - a networking technique}
Digital - operating using (discrete) numbers, as opposed to Analogue. In electronics and computing, this (almost always) means working in Binary - using two discrete voltage (or current, or charge, or switch position) levels to represent ones and zeros, and combining many of these to make larger numbers.
- (Deutches Industrial Norm) A standards body in Germany; DIN-type connectors are used to connect old-style keyboards, and miniature DINs connect PS/2 devices.
- (Digital Versatile Disk - ReWritable) - DVDs used for storing read-only computer data, recordable and erasable/rewritable on a computer using a DVD-RW drive.
- Changing; in computer memory, dynamic RAM will only keeps it's data if it is read or written frequently, a process called "refreshing"; compare with static.
- Electrically-Erasable Programmable Read-Only Memory - a ROM which can be reprogrammed through applying voltages to special "programming" pins. See Flash.
- The most common computer networking (LAN) system; see IEEE 802.3. Developed by Bob Metcalfe at Xerox, then at 3-Com; originally released as a standard by DEC, Intel and Xerox.
- in a computer, small fans are used to cool the power supply, and sometimes other components like the CPU or disks, and sometimes also the graphics card.
- The way the computer organises the data on the disk drives, defining how the sectors, blocks and tracks are numbered and indexed, and how filenames and folders are named and arranged. See FAT and NTFS.
- A serial interface giving high-speed (400Mbits per sec) connections for external disk drives, cameras, video etc. Also know as the IEEE 1394 standard.
- (i) to reprogram an EEPROM; (ii) a type of random-access memory used in digital cameras, MP3 players and memory keys. Available in various formats, including "compact flash" or "smartmedia" cards. Non-volatile - does not lose its contents when there is no power.
- (Front-Side Bus) - In a PC, the connection between the chipset and the main memory. The FSB speed controls the speed of the memory; typically 133MHz.
- a metal component used to carry away heat from an electronic component; there will usually be heat sinks on the processor and on the power-supply components, and sometimes on other parts like disks and graphics processors.
- A base-16 numbering system, using the numbers 0-9, and the letters A-F representing numbers 10-16. Since 24=16, each 4 binary bits can be written as a hex digit. See also Binary)
- (Integrated Device Electronics) - the most common method for connecting internal PC disk drives; each IDE interface can normally connect to two disk drives, a master and a slave drive. Normally connected using flat cables. See also cable select, SCSI Interface.
- A standard for 10Mbps or faster networking (developed from Ethernet); variants of this are the most common networking standard. Most of the PCs in the University use 100Mbps IEEE802.3 networking.
- "interleaving" - drawing only every second line of a video display, so that it takes half the time to scan down the screen, reducing flicker; of course it then takes two scans to draw the whole screen.
- (Industry Standard Architecture) - An old style of expansion slot used to add Expansion Cards on a PC Motherboard. Also called AT slots. Developed for the original IBM AT computer. See also EISA, PCI.
- Lithium Ion - a type of rechargable battery used in laptop computers and other portable equipment. Better than NiMH, and much better than NiCd batteries.
- A free PC operating system based on Unix; there are many versions, for example Red Hat fedora, SuSE, Mandrake. "Paid for" versions with technical support are also available.
- A small (keyring sized) device - usually plugging into the USB, and made from Flash memory - which emulates a disk drive - allowing transfer of files between computers. Also known as a "key drive" or "pen drive".
- (Musical Instrument Digital Interface) A way of writing music as computer code, similar to sheet music. Includes definitions of how hard a note is played, which note and for how long. Can be played through a MIDI-interfaced musical instrument, or a synthesiser on a sound card.
- (MODulator/DEModulator) A device for connecting a computer to a communications line (usually a telephone line); used for connecting PCs to the Internet. (Also connecting FAX machines to other FAX machines across the telephone system.) Speed is measured in bps.
- The main circuit board (PCB) in a PC, which the processor, memory and Expansion Cards plug into. Also usually carries the chipset and interfaces for the printer, USB devices, keyboard etc.
- MPEG-II level 3 file format; a video file format often used to compress music recordings for distribution over the Internet or playing on an MP3 player. See MPG.
- (Original Equipment Manufacturer) - parts packaged for sale to a manufacturer - without "fancy" packing, extra software, instructions, cables etc. Compare with retail.
- The software system that runs the computer, and provides the "user interface", organises the memory and file system, and runs the application programs; examples are Unix, Linux, Windows - all of which come in various versions.
- an error-checking method used in memory; adds an extra bit used to flag if there are an even or odd number of ones in each byte. Special "parity-checked" memory boards and motherboard features are needed for this.
- Printed Circuit Board - a board with electronic circuit components fixed to it and wires "printed" onto it. See Motherboard and Expansion card. Also called a "card".
- (PnP) A system which detects hardware devices connected to the computer, and finds and sets up the software for each device; this means devices can be connected to a computer and automatically work without the user needing to do any "installation".
- The "brain" of the computer: the device that actually runs the program instructions, storing data in the memory, sending data to the outputs and getting data from the inputs. See Celeron, Pentium, AMD and Power-PC.
- (Power Supply Unit) - the device that converts the high-voltage AC electricity from the wall socket into low-voltage DC currents for the computer components. Usually a rectangular metal box in the corner of the case.
- the device, usually run by a battery on the motherboard, which holds the date and time-of-day. Not the same as the processor clock; see also CMOS Memory.
- "update". (i) In graphics displays, this means to redraw the screen; a high "refresh rate" (measured in Hz) means less flicker. Video refresh rates vary between about 50-100Hz. (ii) In dynamic RAM, refreshing prevents the memory from "forgetting" its contents.
- a measure of detail in computer graphics; usually expressed in a number of pixels vertically & horizontally (for a screen) or dots-per-inch (for a printer)
- Red, Green, Blue - the colours used to make all the colours displayed on a computer video screen, and representing colours this way. Also sometimes the connection method for monitors. See also CMYK
- Read-Only Memory; memory which can only be read from, and not written - i.e. permanent, "non-volatile" memory, which keeps its data even without power, and cannot be modified. See EEPROM, RAM, BIOS and video card.
- (Small Computer System Interface, pronounced "scuzzy") - a faster, more flexible method (interface)for connecting disk drives (and other devices) than IDE; there are various versions, which can connect 7 or 15 devices to the computer.
- one bit at a time - compare to Parallel. The Serial interface on some computers (and the USB interface are connections which communicate by sending one bit at a time, along a single wire; see USB, RS232.
- an electronic device, used in computers as a switch. Can be made very small, and to use very little power. Many millions of transistors are now made on each CPUchip, such as the Pentium.
- (Universal Serial Bus) - a method of connecting external devices to the computer, such as printers, keyboards, modems, disk drives etc, using a high speed (12Mbytes per sec) serial interface; designed to be plugged in and out whilst the computer is running, and to be fully "plug-and-play". USB uses two connectors: USB-A & USB-B.
- (a U.S. term; also known as a "valve") an early electronic device, made of glass, with all the air removed. Valves were large and parts of them had to run red-hot; this meant they used a lot of power, and were unreliable. Used in early computers, but replaced in the 1960s by transistors (in TV sets, replaced by transistors in the mid-1970s). Valves are still used as CRT displays, and in guitar amplifiers.
- The PCB that makes the "video signal", or the image, to display on the screen. May be an Expansion Card or built-in (on-board) to the Motherboard. Has it's own processor, clock, RAM and ROM. Also known as VGA card, Graphics card.
- (Wide Area Network) - a computer network spanning a large area, usually between separate organisations and connecting LANs together. An example is the Internet.
- (Pronounced "wizz-ee-wig") - "what you see is what you get" - describes a system where what you see on the screen looks very like what is printed out.
- A version of Windows introduced in 2001. Comes as XP-Home and XP-professional. Office XP is the version of Microsoft Office released at the same time.
- (Zero Insertion Force socket) - a socket for an Integrated Circuit with a mechanism to release or hold the chip without using force on the chip itself. Used for processors.