Guide to Macintosh Jargon

The following list of Macronyms, will hopefully alleviate any doubts you may have had, concerning what things mean.

A/D, ADCAnalogue to Digital Converter. In the "real world", measurements such as temperature, sound, pressure and so on are continuously variable quantities. Digital computers, though, require information in a digital form - one which can be represented as 1s and 0s. An ADC converts the analogue information into those 1s and 0s. For example, newer Macs have a microphone input; this is fed via a built-in ADC so that the Mac can process and manipulate the sound.
See also DAC
A/UXApple's version of the Unix operating system.
See also Unix
Accelerator BoardA board containing a faster CPU, which effectively speeds up the Mac's operation. Specific accelerator boards are available which, for example, just speed up graphics performance rather than the entire Mac. Most accelerator boards take the form of NuBus cards.
See also NuBus
ADBApple Desktop Bus. The connectors which link the keyboard and mouse to the Mac.
AIArtificial Intelligence. This is the term used to describe a computer program which responds in such a way that it seems to have human-like intelligence. Programs which can recognise handwriting, speech input and so on are often referred to as AI systems.
See also Expert System, Intelligent Agent
AliasA tiny representation (but not true duplicate) of a master document or program. Aliases provide easy access to frequently used programs, documents and folders. The alias can be kept anywhere - the Mac will remember where the original is. To make an alias, you click once on the original and then select "Make Alias" from the File menu. Aliases were introduced with System 7.0.
See also Desk Accessory
ANSIAmerican National Standards Institute. A US organisation which sets many of the standards used in computing and computer design.
AppleTalkOften used to mean the software portion of Apple's LocalTalk networking system, although it is fairly interchangeable with the word LocalTalk.
See also LocalTalk
ARMAcorn RISC Machine. A RISC-based microprocessor invented by Acorn, which is used in some Apple LaserWriters.
See also RISC
ASCIIAmerican Standard Code for Information Interchange. A standard set of numeric codes which refer to characters of the alphabet and other symbols. Virtually all text-based programs can translate ASCII codes into the relevant characters, so even if your word processor can't understand anther's file format directly, it will be able to cope with text saved from that program as ASCII. In the Mac world, this is often referred to as "plain text".
ATMAdobe Type Manager. A program written by Adobe, which allows the Mac to display PostScript fonts smoothly on the screen at any size, and which also allows PostScript fonts to be output to non-PostScript printers.
BaudA measure of data speed, often used when referring to modems. Strictly speaking, baud refers to the number of changes between '1' and '0' per second in the data sent but, in practice, can be used synonymously with BPS.
See also BPS, Modem
BBSBulletin Board System. A computer to which you can connect via a modem and phone line. BBSs normally contain discussions on a wide range of topics, and public domain and shareware software which you can 'download' and run on your Mac.
See also CIX, CompuServe, Modem
BetaA program under development is said to be in 'beta stage' when it has had most of the bugs removed but is not yet complete. Beta testers are people whose job is to use the program and report any bugs they find.
Bezier curveA mathematically-specified curve. Named after a French mathematician, they are used in many graphics programs because of the ease with which they can be altered to the exact shape required. (Note that the user doesn't actually have to specify the mathematical formula - that is all taken care of within the program.)
BITBInary digiT. Binary digits are the numbers 1 and 0 - which can be represented in a computer by switching voltage on and off. A bit is the smallest amount of data that a computer can cope with; most computers have memory which can store thousands or even millions of bits.
See also K, M
BitmapA bitmap is a description of individual dots which are either on or off. This defines the appearance of the final image. All output devices such as laser printers and imagesetters are bitmap devices; it is the resolution of the device which determines the quality of the output. The problem with bitmapped images is that one produced on, say, a 72dpi screen will look very coarse when output on a laser printer at 300dpi or an imagesetter at more than 1000dpi. Bitmapped images are often referred to as 'paint' images.
See also Object-oriented, RIP
BootStart up the computer.
BPSBits Per Second. A measure of data transfer speed, often used when referring to modems. It is almost (but not quite) equivalent to baud.
See also Baud, Modem
BugAn error in a program which makes it crash; sometimes this will 'just' mean that you lose the file you are working on, while sometimes it will crash your Mac completely, requiring you to restart it.
ByteA collection of eight bits of data. A byte can have any of 256 values, from 0 to 255.
See also K, M
Cache cardAn add-in card which accelerates the Mac by providing the CPU with some super-fast RAM for storing intermediate results of calculations and the like. Not to be confused with RAM Cache.
CADComputer Aided Design. A CAD program is used in architecture or design to help create plans and blueprints.
See also CAM
CAMComputer Aided Manufacture. Using the computer to control a manufacturing process - for instance, to drive a lathe or even a robot assembly line.
See also CAD
CCITTConsultative Committee for International Telephony and Telegraphy. The international committee which sets most of the standards for data communication, including those used by modems.
See also Modem
CD-ICompact Disc Interactive. A multimedia standard invented by Philips and Sony, based around CD-ROM. This standard is supported by Apple, and some CD-I authoring tools, which allow CD-I discs to be prepared, are now available on the Mac.
CD-ROMCompact Disc Read Only Memory. CD-ROM is the use of CD discs to store data - typically up to 660M or so - in a form which appears to the Mac as though it were a large hard disk. The only differences are that data access is often somewhat slower, and that data cannot be written to CD-ROMs from the Mac - only read from them. CD-ROM is often used to distribute large quantities of data, such as encyclopaedias and archived information, and for multimedia presentations which require huge amounts of data.
CDEVControl panel DEVice. Pronounced "see-dev". A utility program stored in the System folder (under System 7.0 stored in the Control Panel folder). CDEVs usually perform some function associated with the Mac's performance - for instance, the Sound CDEV allows you to alter the volume of the Mac's speaker, the General CDEV provides controls for the current date, time, desktop pattern and so on.
ChooserDesk accessory used for selecting printers, file servers and the like.
See also Desk Accessory
CIXCompulink Information eXchange. A popular UK bulletin board with a wide range of conferences on computing and non-computing related topics, and a large number of downloadable PD and shareware programs.
See also BBS
ClassicA word which reputedly cost Apple around $1 million. When Apple was searching for a name for its new, low-cost, compact Mac, it came up with the word 'Classic' - but a company in Florida already owned the rights to the word in the context of computers. So, according to rumours, Apple bought the rights - for a cool $1 million.
CMY, CMYKCyan, Magenta, Yellow, black ('Key'). The colour system used in full-colour printing. A printing press (or colour printer attached to the Mac) puts cyan, yellow and magenta ink on to paper - combining these colours you can create any other. However, although black can be created by mixing C, M and Y, black ink is often added separately, since the combination of the other three colours can lead to a rather muddy effect.
CompressionThe process of reducing the amount of memory or storage space that data takes up. Compression can either be 'lossless' - when re-expanded, the data is exactly the same - or 'lossy', where some degradation of the data has occurred. Data files, programs and so on are only ever compressed using lossless systems, since it is imperative that the data can be completely recovered. However, image files are often compressed using lossy systems, since a small amount of degradation in the image quality is often unnoticeable.
CompuServeAn American bulletin board which currently has more than 500,000 subscribers. Many software and hardware vendors have 'forums' on CompuServe, where users can ask questions about the products.
See also BBS
Control PanelsSpecial windows that allow modifications to the Macintosh interface. Found in the Control Panels folder in the System Folder, they include Keyboard, Mouse, Sound and Colour modifiers.
CPUCentral Processing Unit. The 'heart' of the computer, this is the chip which does much of the work. The Mac is based around Motorola's 68000 family of chips - the 68000, 68020, 68030 and 68040, in ascending order of power. IBM-compatible PCs are based around the 80x86 family - most current models use the 80486 chips.
CrashA term which means that the Mac has stopped working and will need to be restarted.
DA, Desk AccessoryA small program that, under Systems pre-7.0, was accessible from the Apple menu, even when other programs were running. System 7.0 (and above) allows you to run more than one program at once, and any application can be made accessible from the Apple menu, so DAs are indistinguishable from normal programs.
DACDigital to Analogue Converter. The opposite of an ADC, this converts digital information to analogue form.
DATDigital Audio Tape. This was primarily intended as an audio recording/storage system similar to the cassette tape. However, it is now increasingly being used as a back-up tape system for computers: all the data from a hard disk is saved to tape so that it can be recovered should the hard disk crash. The advantage of using DAT is that large quantities of data can be stored on a tape slightly smaller than a standard audio cassette.
DingbatsCharacters in a font which don't fit into the general categories of letters, numbers or punctuation. LaserWriters are normally shipped with a font called Zapf Dingbats, which is made up of these 'odd' characters such as bullet points, square boxes, arrows and the like.
DownloadThe transfer of data from a BBS or remote computer to your machine, usually via modem.
See also BBS, Modem, Upload
DPIDots Per Inch. A way of measuring the quality of an output device or scanner. Each character or image is made up of several tiny dots on the page; the more dots, the better the image appears. Typically, a laser printer will output 300dpi (although 600dpi machines are becoming more common), while an imagesetter normally outputs at 1270dpi or 2540dpi.
DRAMDynamic Random Access Memory. DRAM stores data as electrical charges on tiny capacitors in the chip.
See also RAM
DrawSee Object-oriented
DTPDeskTop Publishing. The creation of documents - magazine pages, brochures, sales letters and so on - using a computer. The Mac was the first machine to really explore the possibilities of DTP, and it's fair to say that without the invention of the Mac, DTP would be at a far more primitive stage than it is today.
EmailElectronic mail. The idea of electronic mail is that you dispense with normal paper memos, letters and so on, and instead send documents from computer to computer. The advantage is that, rather than writing a memo with your word processor, printing it out and then posting it, you can send the actual document across a network or via modem. The disadvantages are that the recipient must use a computer which is connected to this network or which has a modem attached, and that many people immediately print out copies of any email sent to them - which destroys the whole concept of a 'paperless office'.
EPSEncapsulated PostScript. A graphics file format which combines a PostScript file with a preview image, so that it can be imported into graphics or page make-up packages. The preview image normally doesn't take up much disk space, and is only low-resolution - it's simply there to allow the user to see a representation of what the final, printed version will look like.
See also PostScript
EthernetAn industry standard networking system, using co-axial cables. Much faster than LocalTalk. To connect Macs to an Ethernet network, you must install an Ethernet board in the Mac.
Expert SystemA program which uses artificial intelligence to produce solutions to problems. These are often 'rule-based' programs: an expert programs them with a system of rules, which they use to solve questions posed by users. A typical example is a medical diagnosis program, where the user inputs symptoms and the program uses diagnostic rules to produce a probable cause of illness.
See also AI
ExtensionSee INIT
Fax modemA modem which can also function as a fax machine, transmitting a Mac file to a receiving fax. Some fax modems will also receive faxes, storing them as TIFF files.
File formatThe way in which a file is stored on disk. Different programs have different file formats and can often not read each others. This has led to the creation of some standard file formats so that data can be exchanged between different programs. Typical text formats include ASCII and RTF, image formats include EPS, TIFF and PICT.
FinderThe program which creates the desktop and allows you to access and manage files. This is always loaded when you start up the Mac.
FPUFloating Point Unit. This is a chip which is designed to handle the complex arithmetic very quickly. It is often known as a 'maths co-processor'. Many Macs have a co-processor built-in; most of those that don't can have one fitted as an optional extra. Fitting a co-processor speeds up processor-intensive tasks such as large spreadsheet manipulation and graphics packages.
Front endUsed to refer to the program's appearance to the user - the windows, buttons and so on, via which the user interacts with the program.
G, GbGiga, Gigabyte. A term used to describe memory and disk capacity. One gigabyte is equal to 1024 megabytes.
See also K, M
GUIGraphical User Interface. A system - such as the Mac - which allows you to control the computer through the use of images, icons and the like.
See also Icon, WIMP
HayesA modem manufacturer which set out a standard method of controlling modems by sending the letters 'AT' followed by a one- or two- character command. Modems are known as "Hayes-compatible" if they follow this standard - almost all do.
See also Modem
HFSHierarchical File System. The Mac's file system, which allows applications and documents to be stored in nested folders, rather than all on one 'level', as was the case in the earliest versions of the system.
HSBHue, Saturation, Brightness. A system of specifying colours when displayed on a monitor.
See also RGB, CMYK
IconA pictorial representation of an object; for instance, the standard image of a folder on the Mac desktop is a representation of an actual directory on the hard disk.
ImagesetterAn output device which produces pages on film or bromide; these are then normally used as master pages to print from. Imagesetters have resolutions ranging from 1000dpi to 3000dpi or more.
INITA program which must be located in the System folder of the Mac (in the Extensions folder when running System 7.0). INITs are normally programs which control some form of the Mac's hardware - for example, many scanners require an INIT to make them work properly.
Intelligent AgentA phrase coined by Microsoft to mean a program which performs a task using some amount of artificial intelligence.
See also AI
ISDNIntegrated Services Digital Network. The name for the digital telephone network. If two computers both have the appropriate interface - and access to the ISDN service - they can transfer data across ISDN phone lines at a speed of about 56,000bps
JPEGJoint Photographic Expert Group. A body which sets standards for still image compression. The JPEG standard is now widely used.
K, kKilo. Lower-case 'k' means 1000, so 30k is 30,000. In computing, K means 1024, so a 30K file is actually 30 x 1024 = 30720 bytes in size.
See also Byte, M
KerningThe process of closing up the space between pairs of letters - AV, for example - so they look better together.
LANLocal Area Network. A local area network is one where a number of computers in fairly close proximity to each other are connected together so that they can exchange data and share resources such as printers.
See also Network, WAN
LaserLight Amplification by Stimulated Emission of Radiation. (Not a lot of people know that!) Laser Light can be focussed to a very small point. In laser printers, a laser beam scans a specially coated rotating drum, building up a pattern of electrical charge in the shape of the image to be printed. The drum attracts tiny particles of toner to the charged areas, and these are then transferred to the actual sheet of paper, where they are fixed by heat.
LCDLiquid Crystal Display. LCD units are flat and lightweight, and so are ideal for portable computers. Early LCDs suffered from poor resolution and contrast, but these problems have now been at least partially resolved. For ease of viewing, many LCD screens are 'backlit' - a light is shone from behind the screen, which makes the characters much easier to read. The main problem with LCDs is that rapidly moving objects - such as the Mac's cursor - can blur, making them harder to distinguish.
See also Supertwist
LeadingThe amount of space between one line of text and the next.
LisaThe predecessor of the Mac, the Lisa had a larger screen and a much larger price-tag - several thousand pounds for a single-floppy, no hard disk model. The Lisa was a failure, but was succeeded by the Mac Plus... and the rest is history.
LocalTalkApple's built-in networking system. 'LocalTalk' can mean either just the hardware side of things, or both hardware and software.
See also AppleTalk
LSILarge Scale Integration. This is a guide to the complexity of the circuit on a chip. LSI is used to describe chips the electronic circuitry with equivalent to 100 or more logic 'gates' - the building blocks of digital circuits.
See also VLSI
MMega. Conventionally, mega is used to mean million. In computing, though, 1M is equivalent to 1024K - and since 1K=1024, 1M=1,048,576.
See also K
MbMegabyte. (Sometimes just M is used.) Used to define the capacity of storage systems - RAM, disk, tape or whatever. 1Mb is 1,048,576 bytes.
See also Byte, K
MIPSMillion Instructions Per Second. This is one way of expressing a computer's operating speed.
MMUMemory Management Unit. A chip which looks after the CPU's use of memory in the computer. The MMU can be either built into the CPU itself (as in the 68030 used by some Macs), or can be a separate chip (the 68020 used in the Mac II, for instance, doesn't have a built-in MMU, which means that the Mac II is limited to the amount of memory it can use unless an MMU is fitted).
MODEMMOdulator/DEModulator. A device which changes the digital information output from computers into an analogue signal suitable for sending along a phone line - and vice versa. In essence, this means that two computers equipped with modems can transfer files and data across a phone line.
See also Baud, BBS, BPS
MoireHorrible rosette patterns sometimes produced on printed colour photographs due to screen angles and frequencies clashing.
MonospacedA monospaced font is one where each of the characters occupies the same amount of horizontal space. Courier, for example, is a monospaced font.
See also Proportionally spaced
MPEGMoving Picture Expert Group. A body set up to decide technical standards for storage and compression of moving images - normally video.
See also JPEG
MS-DOSMicrosoft Disk Operating System. The operating system normally used on IBM-compatible PCs. This is a 'command line interface' - which means that all commands have to be typed in from the keyboard.
See also GUI, Windows
MultiFinderBefore System 7.0, MultiFinder allowed more than one application to be open at the same time. System 7.0 has the equivalent of MultiFinder built-in. This does not give a true multi-tasking environment, however - although some programs can continue working in the background, most suspend what they are doing if another application is brought to the front.
MultimediaA somewhat nebulous term; strictly speaking, the integration of elements such as sound, graphics, video and text. 'Multimedia program' is normally used to describe a program which incorporates more than one of these elements.
Multi-taskingThe ability to have more than one program actually performing operations at the same time. System 7.0 (and MultiFinder) allow a very basic form of multi-tasking; it is anticipated that the PowerPC range will allow true multi-tasking.
See also PowerPC
NetworkA connection of computers, printers and the like.
See also LAN, WAN
NTSCNational Television Standard Committee. Normally used to refer to the US television standard.
See also PAL
NuBusThe Mac's system for adding extra hardware. NuBus is an industry-standard connection system, which is consistent across different machines - so, for instance, a NuBus card should work identically when plugged into any model of Mac with NuBus slots. NuBus cards are often used for adding extra monitor support, video capture, accelerators and so on.
Object-orientedA method of describing an image by detailing the actual drawing process, rather than merely reproducing a bitmap. For instance, a square can be described in object-oriented terms by detailing the four corner points and the fact that lines should be drawn between them. The advantage of object-oriented graphics is that they do not depend on the resolution of the output device. Object-oriented graphics are often referred to as 'draw' images.
See also Bitmap
OCEOpen Collaboration Environment. A standard set up by a number of companies, including Apple, which will provide a common 'front-end' to email systems created by different vendors.
See also Email, Front end
OCROptical Character Recognition. Describes devices and/or software which can translate typed or printed text into a computer-readable form. Without OCR, you can scan a page of text and store the resulting image on disk, but you can't edit the text in any way. OCR, on the other hand, translates a page of text into a text file which can then be used just as if it were typed in at the keyboard.
OEMOriginal Equipment Manufacturer. The manufacturer, rather than the distributor, of a device. Often used as in: "Canon OEMs its laser printer engine to Apple". This means that Canon produces the device and sells it to Apple, which adds extra features of its own and then sells it on to users. This process is often known as 'rebadging' - the purchaser replaces the OEMs logo on the device with its own.
OSOperating System. A program which manages the resources of a computer, such as the input/output devices, the available memory and the storage and retrieval of files.
See also MS-DOS
OS/2IBM's GUI, which runs on IBM-compatible PCs. OS/2 is not currently very popular - most people who run a GUI on their PC run Windows.
See also GUI, Windows
PaintSee Bitmap
PALPhale Alternating Line. The television system used in the UK.
See also NTSC
PARCPalo Alto Research Centre, a division of the Xerox Corporation where much early work was done on GUIs.
See also GUI
PCPersonal Computer. Although, strictly speaking, the Mac is a PC, this abbreviation is normally used to mean 'IBM-compatible personal computer'.
PDPublic Domain. Used to describe programs that can be freely copied and distributed. Often authors specify that their program may not be altered in any way, although strictly speaking this is not PD, but Freeware.
See also Shareware
PDAPersonal Digital Assistant. An intelligent electronic notepad that allows freeform note taking, drawing, calculating, scheduling and communicating. Apple's first PDA, the Newton, comes with stylus input for free-form handwriting entry and has been available since 1993.
PDLPage Description Language. A system of controlling a printer or other output device where the details of the image which is to appear on the page are sent to the printer in the form of a list of instructions similar to a programming language; the printer 'rasterises' these into a bitmap, which it then prints.
See also Bitmap, Rasterise, PostScript
PDSProcessor Direct Slot. A connector for expansion cards. Not many Macs have PDS slots, since these are specific to the CPU used in the Mac - most use NuBus expansion slots instead.
See also NuBus
PICTPICTure. A Mac file format where an image is stored in object-oriented format. PICT is the most common Mac graphics format - any image processing program should be capable of importing and exporting PICTs.
PixelPICture ELement. The smallest element of a computer display that can be controlled. The greater number of pixels per inch, the better the resolution of the display. 'Pixels per inch' (ppi) on a monitor is equivalent to 'dots per inch' (dpi) on an output device, and often monitors are described in terms of their dpi, rather than ppi. Most Mac monitors display at 72dpi.
PointA typesetting measurement equivalent to all intents and purposes, to 1/72nd of an inch.
PostScriptA page description language created by Adobe in the early 1980s. PostScript is now the industry standard PDL for professional-quality document production.
See also DTP, EPS, PDL
PowerPCA collaboration between Apple, IBM and Motorola that resulted in a new generation of computers based on a RISC chip, which run far faster than current PCs. PowerPCs are able to run Mac and OS/2 applications, as well as programs written specifically for them. The first PowerPC came from Apple in 1994.
See also RISC
PRAMParameter RAM. A small portion of the Mac's memory which stores information such as the current date and time, and user settings for things like the desktop pattern and speaker volume. PRAM has a battery back-up, so it is not erased when the Mac is switched off.
Programmer's switchTwo small switches which allow the Mac to be restarted without actually turning the power off, if it has crashed. On some Macs these take the form of two small pieces of plastic protruding from the front or side of the case - on the Quadras they are actually small buttons on the front of the case, and on the LC and IIsi they don't exist. One switch restarts the Mac, the other calls up a machine code monitor, which is only used by programmers - if you get a small white rectangle in the middle of the screen, you've pressed the wrong one, and you should press the other. The programmer's switch should only be used if you're sure that your Mac has crashed - remember that if you restart, you will lose whatever you've been working on.
Proportionally spacedA proportionally spaced font is one where different letters take up different amounts of horizontal space - for example, the amount of space taken up by the letter 'i' is much less than that taken up by 'W'. Proportionally spaced fonts look much more elegant than monospaced fonts.
See also Monospaced
PSSPacket Switching Stream. A technique for sending data over the BT network of phone lines. Data plus destination information is assembled as a string of information called a 'packet'. The packet enters the network, and at each major junction ('node') the destination address is read and used to send the packet to the next appropriate node. Normally, the user pays a fixed fee per packet sent or received, rather than a fee based on the distance that the data is sent, so this form of data transfer is more cost-effective than a direct-dial call.
PSUPower Supply Unit. The circuitry inside the computer which changes the 240V mains power supply into the lower DC voltages that the computer requires.
Publish/SubscribeApple's system of transferring data between applications; you Publish data from one file, and Subscribe to it in another. If the data is altered in the published file, that change will automatically be reflected in the subscribing file.
QuickDrawA set of graphics commands built in to the System that controls how the Mac draws graphics and text on the screen. Also used for output to devices which don't have a PostScript interpreter.
See also PostScript
QuickTimeApple's standard format for storage and display of moving images and sound. QuickTime also incorporates data compression algorithms, both for still and moving images. Although Apple designed QuickTime, it has now been licensed by a number of other vendors, so ensuring its success as a cross-platform standard.
RAMRandom Access Memory. The standard memory in a computer, in the form of chips, used to store the program and data currently running. RAM is measured in kilobytes or megabytes; Macs can have between 1M and 128M of RAM installed. RAM loses its data when the Mac is switched off - so all data must be saved to a storage device such as a hard disc.
RAM cacheAn area of memory used to hold information recently read from disk - so if the information is needed again, it can be retrieved from memory, which is faster than accessing the disc. The size of the RAM cache is set from the Memory Control Panel under System 6.0. Not to be confused with Cache card.
RasteriseThe process of converting a page description into a bitmap; the action of a RIP.
See also RIP, PDL
RGBRed, Green, Blue. a form of specifying colour, normally used when referring to colours produced by a monitor, since monitors have three electron 'guns', one each for red, green and blue.
See also CMYK, HSB
RIPRaster Image Processor. A device which converts a page description in a PDL - typically PostScript - into a bitmap which the output device can then print. Desktop laser printers normally have the RIP built-in, whereas many imagesetters require an external RIP.
See also Bitmap, Imagesetter, PDL, PostScript
RISCReduced Instruction Set Computer/Chip. Traditional microprocessors, such as Motorola's 680x0 series used in the Mac, have long lists of operations they can perform (known as the 'instruction set'). However, much of the time only a small proportion of those instructions are used, so RISC chips were designed to take advantage of this. Not only is the size of the instruction set reduced, but the remaining instructions can be executed more efficiently, increasing the processing speed of the chip. Those instructions which have been omitted ca be simulated when necessary by combining a number of the remaining instructions. PowerPC, the next generation of Macs, will use a RISC chip for increased speed.
See also ARM, PowerPC
ROMRead-Only Memory. Any memory device from which the contents may be read but not written; normally used when referring to chips inside the computer that contain part of the operating system.
See also CD-ROM, RAM
RTFRich Text Format. A text file format created by Microsoft which contains not only the text but also some formatting details such as margins, tabs and fonts used. A number of word processors can be read RTF files.
Sans-serifA sans-serif font is one which has no decorative elements - its characters tend to be simply designed, and to have a fairly 'stern' look, Helvetica is an example of a sans-serif font.
See also Serif
SCSISmall Computer System Interface. Pronounced 'scuzzy'. This is a means of connecting devices such as hard disks, CD-ROM players and tape drives to a computer. Each device is 'daisy-chained', and up to eight can be connected in total. The Mac and any internal hard disk each count as one device, allowing up to six external devices to be connected. Each SCSI device has a unique 'ID' number between 0 and 7 - the Mac is always device number 7.
SerifThe 'twiddly bits' on a font such as Times which make it look more decorative - and which also make it easier to read.
See also Sans-serif
SharewareA form of 'try-before-you-buy' software. The software can be freely distributed, but if you like it and continue to use it, you are required to send money to the author. Much of the Mac's best-known utility software, such as the StuffIt file compressor, started life as shareware.
SIMMSingle In-line Memory Module. A small circuit board containing memory chips and ancillary circuitry. To expand the memory of the Mac, you add RAM into special 'banks' of connectors attached to the main circuit board, which accept SIMMs. The capacity of a single SIMM typically ranges from 1M to 16M (64M SIMMs are now available), although the Mac requires that, to add SIMMs, each bank of connectors (either two or four, depending on the Mac) must be completely full or completely empty, which restricts the number of different memory configurations available.
See also M, RAM
SupertwistThe form of display used on Apple's high-end portable computers - the PowerBook 170 and 180. SuperTwist displays look similar to LCDs, but the amount of blurring produced when items move around the screen is vastly reduced.
See also LCD
SYLKSYmbolic LinK. A file format for exchanging data between different spreadsheets.
SyQuestA proprietary name which refers to a form of removable hard disks that have become the de facto standard for transferring large quantities of data. Two versions exist: 40M, and the rather less popular 80M.
TIFFTagged Image File Format. A widely-supported bitmap graphic file format, particularly suited to images produced by scanners.
See also Bitmap, File Format
Trojan HorseA program which has been written to help transport a virus from computer to computer. Trojan horse programs usually have appealing names such as 'Super 3D Racecar', so that as many users as possible will run them. When they are run, they spread the virus into the system.
TrueTypeA font format created by Apple and Microsoft as an alternative to PostScript fonts. TrueType fonts are scalable, which means they will appear smooth at any size, and on any output device. However, PostScript fonts are still normally used for professional-quality DTP work. A PostScript output device will be able to image TrueType fonts, so it is possible to mix TrueType and PostScript in the same document.
See also PostScript
UnixAn operating system written by Bell Laboratories in the US, which is often used on mainframe and minicomputers, and which is very popular in educational institutions. Versions of Unix can be bought to run on the Mac, such as Apple's own A/UX.
See also A/UX, Operating system
UploadThe transfer of data from your computer to a remote machine or BBS, usually via modem.
See also BBS, Download, Modem
VapourwareThe name given to software which was announced by its manufacturers some time ago, but which has still not been shipped.
Virtual memoryA method of 'fooling' the computer into thinking it has been more RAM than it really does, by switching memory contents to and from spare space on a hard disk. If you use virtual memory on your Mac, you can run more programs at once, but you will find that speed is decreased - due to continually swapping memory contents to and from disk.
See also RAM
Virtual realityAny form of imaginary 'space' created in a computer. Current usage refers to a computer-generated world that you see in three dimensions by wearing a helmet with two tiny screens, the displays of which combine to form the 3D image. Interaction with this visual world is normally achieved by wearing a glove-like device which contains sensors to detect your hand movements. Moving your hand causes an image of a hand displayed on the screens to move.
VirusA program which is designed to spread from computer to computer without the user's knowledge. Some viruses are harmless, while others can wipe off all the data from a hard disk. Viruses can be detected and removed using an anti-virus software such as the public domain program, Disinfectant.
See also Trojan Horse
VLSIVery Large Scale Integration. A VLSI chip is one where the circuit is equivalent to at least 1000 logic 'gates'. VLSI chips are widely used in computers.
See also LSI
WANWide Area Network. A network of computers where the distances between the machines are large. Often the connection is via modem or land lines which run underground from one site to another.
See also LAN, Network
WIMPWindows, Icons, Mouse, Pointer. An older term, now superseded by the more fashionable 'GUI'.
See also GUI
WindowsA GUI written by Microsoft to run on IBM-compatible PCs. Similar in some respects to Apple's Mac interface - which resulted in a long-lasting court case between the two companies, with Apple accusing Microsoft of using copyrighted concepts.
See also GUI, OS/2
WORMWrite Once, Read many times. This generally refers to optical storage devices which use a laser beam to write data by etching the specially-coated surface of a disk or tape. A lower-power laser is then used to read the data. Once written, the data cannot be altered - hence the name.
WYSIWYGWhat You See Is What You Get. This refers to programs which display on-screen exactly what you will get when the document is printed out. The Mac was one of the earliest computers to utilise WYSIWYG.

Please send any comments on this page to:
(George W. Mills, Computing Service, University of Glasgow)