ar	Apple Publications
	Glossary
	
	Version 3.0
	August 1988


a Apple Computer, Inc.
  
Copyright c 1988 by Apple Computer, Inc.
  
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, electronic, photocopying, recording, or otherwise, without prior written permission of Apple Computer, Inc.  

Apple, the Apple logo, AppleTalk, Apple IIgs, AppleWorks, HyperCard, ImageWriter, LaserWriter, Macintosh, MacTerminal,  and ProDOS are registered trademarks of Apple Computer, Inc.
  
AppleCD SC, Apple Desktop Bus, AppleFax, AppleMouse, AppleShare, Apple Writer, A/UX, EtherTalk, Finder, HyperTalk, LaserShare, and LocalTalk are trademarks of Apple Computer, Inc.
  
AppleWorks is a registered trademark of Apple Computer, Inc., licensed to Claris Corporation.
  
MacDraw, MacWrite, MacPaint, and MacProject are registered trademarks of Claris Corporation.
  
CP/M is a registered trademark of Digital Research, Inc.  

Ethernet is a registered trademark of Xerox Corporation.
  
ITC Avant Garde Gothic, ITC Garamond, and ITC Zapf Dingbats are registered trademarks of International Typeface Corporation.
  
Microsoft and MS-DOS are registered trademarks of Microsoft Corporation.  
NuBus is a trademark of Texas Instruments.
  
PC-DOS is a registered tradkmark of International Business Machines Corporation.
  
PostScript is a registered trademark of Adobe Systems, Incorporated.
  
UNIX is a registered trademark of AT&T Information Systems.


Contents


Using the Apple Publications Glossary  v

Listings	1   
Glossary A  1
Glossary B  7
Glossary C  11
Glossary D  19
Glossary E  27
Glossary F  31
Glossary G-H  37
Glossary I-J  41
Glossary K-L  47
Glossary M  53
Glossary N-O  59
Glossary P-Pk  63
Glossary Pl-Pz  67
Glossary Q-R  73
Glossary S-Sk  79
Glossary Sl-Ss  85
Glossary St-Sz  89
Glossary T  93
Glossary U-Z  97
Appendix
Creating a Glossary for Your Manual  101

Audience considerations  102
	Know your audience  102
	Make definitions explanatory as well as correct  103
	Make the context clear  103
	Connect ordinary usage with technical meaning  103
Matters of form  103
	Galaxy Design  103
	Format of an entry  104
	Alphabetization  104
	Parts of speech  104
	Pronunciation  104
	Cross-references  105
	Multiple definitions  106
	Independence  106
Assembling the glossary  106

P	R	E	F	A	C	E


Using the 
Apple Publications Glossary





THIS GLOSSARY IS AVAILABLE ON DISK FOR EASY ELECTRONIC CUTTING  
and pasting. If you want a disk copy, contact Developer Services.

Use this glossary as a starting point for constructing a glossary for your own manual. Copy those entries you want to include and add any other terms you think your readers will need. If you think other terms should be added to this glossary, pass them on to:

 	Deborah Robbins
	Apple Computer, Inc.
	20525 Mariani Avenue
	Cupertino, CA 95014 

This glossary includes some basic definitions as well as more technical information. Where there is more than one definition for a term, the first definition is usually the simplest or most general one; the other definitions often give more complex technical meanings. If your manual is intended for beginners, you might want to keep only the first part; if your manual is a reference, you might want to eliminate the simple definition and even expand on the technical definition.  Many terms also have a number of definitions depending on the language, system, or other context.  


s  Important

The definitions have been compiled from individual glossaries written for Apple manuals. They have not necessarily been verified for technical accuracy. If you find an error, please bring it to our attention.s



Boldfaced terms within a definition are also defined in the glossary: be sure to include those terms in your own manual glossary. (If that's not desirable, change the boldface to plain text so readers won't be confused.) 
 

s  Important

Although usage of a term may be implied by its definition, this glossary is not a guide for correct Apple usage. See the Apple Publications Style Guide for usage rules.  s


The appendix, "Creating a Glossary for Your Manual," describes Apple standards for glossary sections and how to write glossary entries.  It was written by David Bice, Technical Writer, Developer Products Technical Publications, and Jody Larson, Senior Developmental Editor, Publication Services.  


Glossary A


absolute: Characteristic of a load segment or other program code that must be loaded at a specific address in memory and never moved. Compare relocatable.
  
absolute pathname: The complete name of a file, given by listing all of the directories leading down to that file, starting from root ( / ) and concluding with the filename itself. The directories leading to the file are separated from each other and from the filename by slashes. For example, /etc/passwd is the absolute pathname of the system password file, passwd, located in the etc directory beneath the root ( / ) directory. 
 
accelerator card: An expansion card that contains another processor that shares the work normally performed only by the computer's main microprocessor. An accelerator card speeds up processing time.
  
access byte: An attribute of a ProDOS 16 file that determines what types of operations, such as reading or writing, may be performed on the file.  
accessory: See desk accessory, peripheral device.
  
access privileges: The privileges to open and make changes to folders and their contents; they are given to or withheld from users. By setting access privileges, you can control access to confidential information stored in folders on a server.
  
Access Privileges window: When using the AppleShare file server, a window that displays the access privileges, owner, group, and other information about a folder or volume. You use the Get Privileges command in the File menu of the Finder or the Access Privileges desk accessory in the Apple menu to display the window and to review, set, or change access privileges for a folder or volume.
  
accumulator: The register in a computer's central processor or microprocessor where most computations are performed.
  
ACIA: Abbreviation for Asynchronous Communications Interface Adapter; a type of communications IC used in some Apple computers. An ACIA converts data from parallel to serial form and vice versa. It handles serial transmission and reception and RS-232-C signals under the control of its internal registers, which can be set and changed by firmware or software. Compare SCC. 
 
ack cycle: The last period of a transaction during which /ACK is asserted by a slave responding to a master. 
 
acoustic coupler: A type of modem with a cradle that uses a standard telephone handset for transmission. 
 
ACPC: Acronym for Apple Communications Protocol Card (pronounced "ACK-pick"); a parallel interface card that lets an Apple II-family computer communicate and exchange files with other Apple II computers or with most IBM host computers. 
 
acronym: A word formed from the initial letter or letters of the main parts of a compound term, such as ROM (from read-only memory or Fortran (from Formula Translator). 
 
activate: To make a nonactive window active by clicking anywhere inside it.  

activate event: An event generated by the Window Manager when an inactive window becomes the active window.
  
active window: The frontmost window on the desktop; the window where the next action will take place. An active window's title bar is highlighted.
  
activity report: A report created by the AppleFax application that shows the status of the envelopes in your current document's Envelope View. Each AppleFax document has its own activity report.
  
actual parameter: A variable within a program that is passed to a procedure for processing. Compare formal parameter.
  
ADB: See Apple Desktop Bus. 
 
ADB device table: A structure in the system heap that lists all devices connected to the Apple Desktop Bus.
  
ADC: See analog-to-digital converter.
  
address: (1) A number that specifies the location of a single byte of memory. Addresses can be given as decimal or hexadecimal integers. The Apple IIgs has addresses ranging from 0 to 16,777,215 (in decimal), or from $00 0000 to $FF FFFF (in hexadecimal). A complete address consists of a 4-bit bank number ($00 to $FF) followed by a 16-bit address within that bank ($0000 to $FFFF). (2) In data transmission, a code for a specific terminal. Multiple terminals on one communication line, for example, must have unique addresses. (3) A set of instructions that tell your AppleFax Station where, when, and how to send an envelope. The instructions include such information as the phone number to dial and the receiving fax station's password, if any. You make addresses with the New Address command in the AppleFax application. See also address book, envelope.
  
address book: A file that stores addresses and distribution lists. You make an address book with the Save Address Book command or the Save Address Book As command in the AppleFax application. See also address, distribution list.
  
address-book entry: Either an address or a distribution list in an address book.
  
address bus: The path along which the addresses of specific memory locations are transmitted. The width of the path determines how much memory can be used (addressed) directly by the computer. For an n-bit-wide address bus, the computer can use 2n locations in memory where information can be stored. In the Macintosh II, for example, the 32-bit address bus permits the processor to access 232 (4.3 billion) memory addresses. This is more than 250 times as much memory as computers with a 24-bit bus (or the Macintosh II in 24-bit mode) can address (224 = 16.8 million).
Address List: An area in the lower-left part of the AppleFax document window that displays the addresses and distribution lists for the current address book.
  
address mapping: Creating a mapped set of 24-bit addresses by ignoring the 8 highest bits of a 32-bit longword. Either of the two memory management units (MMUs) that can be used on the Macintosh II can accomplish this action when the Macintosh II is operating in 24-bit mode. Address mapping provides compatibility with applications for classic Macintosh machines.
  
address mark: Information that's used internally by the Disk Driver, including information it uses to determine the position of a sector on a disk.
  
address space: A range of accessible memory.
  
administrator: The person who sets up a file server, registers users and their passwords, creates AppleShare groups, and maintains the server.  

ALAP: See AppleTalk Link Access Protocol.
  
Alarm Clock: A desk accessory that displays the current date and time and lets you set an alarm.
  
alert: A warning or report of an error in the form of an alert box, a sound from the computer's speaker, or both. See also alert box.
  
alert box: A box that appears on the screen to give a warning or to report an error message. Its appearance is usually accompanied by a sound warning such as a beep.
  
algorithm: A step-by-step procedure for solving a problem or accomplishing a task.
  
alias: (n.) An alternate name used to invoke or identify a command, a network host, a list of users, or some other applicable entity. (v.) To provide an entity with an alternate name. 
 
alignment notch: A notch on the printer that indicates where to position the left edge of a sheet of paper.
  
A-line instructions: Unimplemented 68000-family instructions, used by the Macintosh to implement Toolbox and Operating System calls.
  
allocate: To reserve an area of memory for use. 
 
American Simplified Keyboard: See Dvorak keyboard.
  
American Standard Code for Information Interchange: See ASCII.
  
amplitude: The maximum vertical distance of a periodic wave from the horizontal line about which the wave oscillates.
  
AMU: The built-in address management unit on the Macintosh II. The AMU handles only 24-to-32-bit address translation and is not a true memory management unit like the optional PMMU. Sometimes called the HMMU.  
analog: (adj.) Varying smoothly and continuously over a range, rather than changing in discrete jumps. For example, a conventional 12-hour clock face is an analog device that shows the time of day by the continuously changing position of the clock's hands. Compare digital.
  
analog data: Data in the form of continuously variable quantities. Compare digital data.
  
analog RGB: A type of color video monitor that accepts separate analog signals for the red, green, and blue color primaries. The intensity of each primary can vary continuously, making possible many shades and tints of color.
  
analog signal: A signal that varies continuously over time, rather than being sent and received in discrete intervals. Compare digital signal.
  
analog-to-digital converter (ADC): A device that converts quantities from analog to digital form. For example, computer hand controls convert the position of the control dial (an analog quantity) into a discrete number (a digital quantity) that changes in steps even when the dial is turned smoothly.
  
analog transmission: Transmission of a continuously variable signal as opposed to a discretely variable signal. Compare digital transmission.
  
AND: A logical operator that produces a true result if both of its operands are true, and a false result if either or both of its operands are false. Compare exclusive OR, NOT, OR.
  
ANSI: Acronym for American National Standards Institute, which sets standards for many technical fields and provides the most common standard for computer terminals.
  
Apple Desktop Bus (ADB): A low-speed, input-only serial bus with connectors on the back panel of the computer that you use to attach the keyboard, mouse, and other Apple Desktop Bus devices, such as graphics tablets, hand controls, and specialized keyboards.
  
AppleFax: The combination of the AppleFax modem, the AppleFax application, and the AppleFax resource. Together with a Macintosh Plus, a Macintosh SE, or a Macintosh II, AppleFax creates a system that links your Macintosh to other AppleFax stations or fax machines. 
 
AppleFax address: An address that represents an AppleFax Station.
  
AppleFax application: A program that lets you send and receive fax files and Macintosh files.
  
AppleFax-distribution list: A distribution list that's made up of AppleFax addresses.
  
AppleFax document: A document that you create with the AppleFax application. An AppleFax document tells your AppleFax Station what files and documents to send, and when, where, and how to send them.
  
AppleFax Preferences file: A file that stores your station's name, password, phone number, and dialing mode. You can set these options with the Fax Setup command in the AppleFax application.
  
AppleFax resource: A system file that lets your Macintosh communicate with the AppleFax modem. With the AppleFax resource, you can send a single fax file from within an application to a fax machine or an AppleFax Station. See also resource.
  
AppleFax Station: A Macintosh equipped with a hard disk, the AppleFax modem, the AppleFax application, and the AppleFax resource.  

Apple HD SC Setup: A utility program that you use to initialize and test SCSI hard disks.
  
Apple key: See Command key, Open Apple key, Solid Apple key.
  
Apple menu: The menu farthest to the left in the menu bar, indicated by an Apple symbol, from which you choose desk accessories.
  
Apple I: The first Apple computer. It was built in a garage in California by Steve Jobs and Steve Wozniak.
  
Applesoft BASIC: The Apple II dialect of the BASIC programming language. An interpreter for creating and executing Applesoft BASIC programs is built into the firmware of computers in the Apple II family. Compare Integer BASIC. See also BASIC.
  
AppleTalk Link Access Protocol (ALAP): The lowest-level protocol in the AppleTalk architecture, managing node-to-node delivery of frames on a single AppleTalk network.
  
AppleTalk Manager: An interface to a set of device drivers that enable programs to send and receive information via an AppleTalk network. 
 
AppleTalk network system: The system of network software and hardware used in various implementations of Apple's communications network.
  
AppleTalk Transaction Protocol (ATP): An AppleTalk protocol that's a Datagram Delivery Protocol (DDP) client. It allows one ATP client to request another ATP client to perform some activity and to report the activity's result as a response to the requesting socket with guaranteed delivery. See also Datagram Delivery Protocol. 
 
Apple II: A family of computers, including the original Apple II, the Apple II Plus, the Apple III, the Apple IIe, the Apple IIc, and the Apple IIgs. Compare standard Apple II. 
 
Apple IIc: A transportable personal computer in the Apple II family, with a disk drive and 80-column display capability built in.
  
Apple IIe: A personal computer in the Apple II family with seven expansion slots and an auxiliary memory slot that allow the user to enhance the computer's capabilities with peripheral and auxiliary cards.
  
Apple IIe 80-Column Text Card: A peripheral card that plugs into the Apple IIe's auxiliary memory slot and allows the computer to display either 40 or 80 characters per line.
  
Apple IIe Extended 80-Column Text Card: A peripheral card that plugs into the Apple IIe's auxiliary memory slot and allows the computer to display either 40 or 80 characters per line while extending the computer's memory capacity by 64K.
  
Apple IIgs: A personal computer in the Apple II family; gs stands for graphics and sound. The Apple IIgs features super high-resolution graphics, 15-voice sound capabilities, and 256K of RAM with a memory expansion slot for adding from 1 to 8 megabytes of RAM.
  
Apple IIgs Interface Libraries: A set of interfaces that enable you to access Toolbox routines from C.
  
Apple IIgs Programmer's Workshop (APW): The development environment for the Apple IIgs computer. It consists of a set of programs that facilitate the writing, compiling, and debugging of Apple IIgs applications.  
Apple IIgs tools: See toolbox.
  
Apple II Pascal: A software system for the Apple II family that lets you create and execute programs written in the Pascal programming language. Apple II Pascal was adapted by Apple Computer from the University of California, San Diego, Pascal Operating System (UCSD Pascal).
  
Apple II Plus: A personal computer in the Apple II family with eight expansion slots and 48K of RAM, expandable to 64K with a language card in slot 0. 
 
Apple III: An Apple computer; part of the Apple II family. The Apple III offered a built-in disk drive and built-in RS-232-C (serial) port. Its memory was expandable to 256K.
  
application: (1) Short for application program. (2) On the Apple IIgs, a program (such as the APW Shell) that accesses ProDOS 16 and the Toolbox directly, and that can be called or exited via the QUIT call. ProDOS 16 applications are file type $B3.
  
application font: The font your application will use unless you specify otherwise-in Roman-based scripts, the application font is Geneva. 
 
application heap: The portion of the heap available to the running application program and the Toolbox. 
 
application list: A data structure, kept in the Desktop file, for launching applications from their documents in the hierarchical file system. For each application in the list, an entry is maintained that includes the name and signature of the application, as well as the directory ID of the folder containing it. 
 
application program: (1) A program that performs a specific task, such as word processing, database management, or graphics. Also called an application. Compare controlling program, system program. See also shell application. (2) A program that runs stand-alone. An application's file type is 'APPL'. 
 
application software: A collective term for application programs. 
 
application space: Memory that's available for dynamic allocation by applications.
  
APW: see Apple IIgs Programmer's Workshop.
  
APW Debugger: A 65816 assembly-language code debugger provided with Apple IIgs Programmer's Workshop.
  
APW Editor: The program within Apple IIgs Programmer's Workshop that allows you to enter, modify, and save source files for all APW languages.
  
APW Linker: The linker supplied with Apple IIgs Programmer's Workshop. 
 
APW Shell: The shell program of the Apple IIgs Programmer's Workshop. The APW Shell provides the interface between APW programs and ProDOS and between the user and APW. 
 
arbitration contest: The mechanism used to choose which of two or more cards requesting control of the bus will become the next bus master. The arbitration contest requires two bus periods (at 100 uS each).
  
archive: (n.) (1) A collection of object files, plus a table of contents. Archives are used mainly as libraries to be searched by the link editor ld. (2) Any collection of files saved simultaneously for backup purposes, usually intended for longer storage than are daily backups. Compare backup. (v.) To save a collection of files for storage. Compare back up.
  
argument: (1) A value on which a function or statement operates; it can be a number or a variable. For example, in the BASIC statement VTAB 10, the number 10 is the argument. Compare operand. (2) A piece of information included on the command line in addition to the command; the shell passes this information to the command, which then modifies its execution in some particular way. Filenames, for example, are often supplied as arguments to commands, so that a command will operate on the named file.
  
argument list: All the arguments passed to a program.
  
arithmetic expression: A combination of numbers and arithmetic operators (such as 3 + 5) that indicates some operation to be carried out. 
 
arithmetic operation: One of the five actions computers can perform with numbers: addition, subtraction, multiplication, division, and exponentiation. 
 
arithmetic operator: An operator, such as +, that combines numeric values to produce a numeric result. Compare Boolean operator, relational operator. 
 
armature: In the ImageWriter print head, the movable member of the mechanism that drives the striker wire. The striker wire is attached to one end of the armature at a right angle. The armature with its striker wire is pulled toward the platen by an electromagnet and is pulled back from the platen by a spring. 
 
ARPANET: A wide area network that links government, academic, and industrial installations around the world. Primarily connecting research sites, the ARPANET was developed in the 1960s by the Advanced Research Projects Agency of the U.S. Department of Defense. See also Defense Data Network. 
 
array: An ordered collection of information of a given, defined type. Each element of the array can be referred to by a numerical subscript.  
arrow keys: The four directional keys in the lower-right corner of the keyboard. You can use the arrow keys to move around in an application.
  
ascent: The vertical distance from a font's base line to its ascent line. 
 
ascent line: A horizontal line that coincides with the tops of the tallest characters in a font. See also base line, descent line, x-height. 
 
ASCII: Acronym for American Standard Code for Information Interchange (pronounced "ASK-ee"). A standard that assigns a unique binary number to each text character and control character. ASCII code is used for representing text inside a computer and for transmitting text between computers or between a computer and a peripheral device. Compare EBCDIC. See also high ASCII characters, low ASCII characters.
  
aspect ratio: The ratio of an image's width to its height. For example, a standard video display has an aspect ratio of 4:3.
  
assembler: A language translator that converts a program written in assembly language (source code) into an equivalent program in machine language (object code). The opposite of a disassembler. Compare compiler, interpreter.
  
assembly: The process of translating source files into object files. 
 
assembly code: A source file written in a low-level programming language that corresponds to a specific computer's binary machine language.
  
assembly language: A low-level programming language in which individual machine-language instructions are written in a symbolic form that's easier to understand than machine language itself. Each assembly-language instruction produces one machine-language instruction. Because assembly-language programs require very little translation, they can be very fast. See also machine language.
  
asterisk (*): In C, the 32-bit pointer data type. 
 
asynchronous: Not synchronized by a mutual timing signal or clock. Compare synchronous.
  
asynchronous communication: See asynchronous transmission.
  
Asynchronous Communications Interface Adapter: See ACIA.
  
asynchronous execution: A method of routine execution that leaves a program free to perform other tasks until the routine is completed. 
 
asynchronous I/O: The capability to perform an I/O operation while its calling process continues to run. With synchronous I/O, the calling process "sleeps" until the I/O operation is finished.
  
asynchronous transmission: A method of data transmission in which the receiving and sending devices don't share a common timer, and no timing data is transmitted. Each information character is individually synchronized, usually by the use of start and stop bits. The time interval between characters isn't necessarily fixed. Compare synchronous transmission. 
 
ATP: See AppleTalk Transaction Protocol. 
 
attention cycle: The name given to a particular kind of start cycle, one in which both /START and /ACK are asserted.
  
audio jack: A connector on the back panel of the computer to which you can attach headphones or other audio devices. 
 
auto-key event: An event generated repeatedly when the user presses and holds down a character key on the keyboard or keypad.
  
automatic variable: In C, a dynamic local variable that comes into existence when a function is called and disappears when it is exited.
  
auto-repeat feature: A feature of keys on computer keyboards; when a key is pressed down and held, the computer will automatically repeat that key's character until the key is released. 
 
A/UX command: The name of a program or a built-in shell command that can be invoked under the A/UX operating system. For example, ls is a program that prints directory information to the terminal; typing ls as a command causes the program to execute. See also built-in shell command, program. 
 
auxiliary slot: The special expansion slot inside the Apple IIe used for the Apple IIe 80-Column Text Card or Extended 80-Column Text Card, and for the RGB monitor card. The slot is labeled AUX. CONNECTOR on the circuit board. See also expansion slot.
 


Glossary B 

back cover: The cover at the rear of the ImageWriter LQ that protects the forms tractor. 
 
background: (1) A relatively inconspicuous place. A program operates "in the background" if it continues to function automatically while you use another program. See also background job. (2) In HyperCard, a card's basic template, which is shared by a number of cards. The background is composed of the background picture, background fields, and background buttons.  

background activity: A program or process that runs while the user is engaged with another application.  

background button: In HyperCard, a button that appears on all cards with the same background. The button's actions are the same on all the cards. Compare card button.  

background field: In HyperCard, a field whose size, position, and text attributes remain constant on all cards associated with a particular background, but whose text changes from card to card. Compare card field.  

background job: A process executed by the shell in which the shell is not suspended while waiting for the process to finish. By default, a process starts in the foreground, and the shell waits until the process has finished executing before the shell returns its prompt. You run a process in the background by appending an ampersand character (&) to the end of a command line; the shell prompt reappears instantly, allowing you to run multiple processes simultaneously. Compare foreground job.  

background picture: In HyperCard, a picture that applies to a series of cards. You see the Background picture by choosing Background from the Edit menu. Compare card picture.  

background printing: Printing from one application while another application is running.  
background processing: In multitasking environments, the operating system's ability to process lower-priority tasks while you perform other work on the computer.  

back out: A method of retracting pin-feed paper, without removing it from the printer, to make printing a single sheet easy.  

back panel: The rear surface of the computer, which includes the power switch, the power connector, and connectors for peripheral devices.  

backslash (\): The "backward slash" character; often used as an escape character.  

backspace: To move to the left in a line of text, erasing the character or selection; thus synonymous with delete.  


Backspace key: A key that backspaces over and erases the previously typed character or the current selection. Its function is identical to that of the Delete key on newer Macintosh keyboards.  

backup: (n.) A copy of a disk or of a file on a disk. It's a good idea to make backups of all your important disks and to use the copies for everyday work, keeping the originals in a safe place. (Some program or startup disks cannot be copied.) Compare archive.  

back up: (v.) To make a spare copy of a disk or of a file on a disk. Backing up your files and disks ensures that you won't lose information if the original is lost or damaged. Compare archive.  

backup bit: A bit in a file's access byte that tells backup programs whether the file has been altered since the last time it was backed up.  

bandwidth: The range of frequencies a device can handle. Bandwidth and maximum data transfer rate are directly proportional. For example, a video monitor's greater bandwidth allows it to display more information per scan frame than most home television sets can. To display 80 columns of text, a monitor should have a bandwidth of at least 12 megahertz.  

bang: A slang term for the exclamation point (!), used as a syntactical element by the C shell, by uucp, and by other utilities.  

bank: A 64K (65,536-byte) portion of the Apple IIgs internal memory. An individual bank is specified by the value of one of the 65C816 microprocessor's bank registers.  

bank-switched memory: On Apple II computers, the part of language card memory in which two 4K portions of memory have the same address range ($D000 to $DFFF).  

banner page: A printed page generated by an AppleShare print server to identify a printed document.  

base address: In indexed addressing, the fixed component of an address.  

base line: A horizontal line that coincides with the bottom of each character in a font, excluding descenders (tails on letters like p).  

BASIC: Acronym for Beginners All-purpose Symbolic Instruction Code; a high-level programming language designed to be easy to learn. Two versions of BASIC are available from Apple Computer for use with all Apple II-family systems: Applesoft BASIC (built into the firmware) and Integer BASIC.  

BASICOUT: The routine that outputs a character when the 80-column firmware is active.  

battery RAM: RAM on the Macintosh and Apple IIgs clock chips. A battery preserves the clock settings and the RAM contents when the power is off. Control Panel settings are kept in battery RAM.  

baud: (1) A unit of data transmission speed: the number of discrete signal-state changes (signal events) per second. Often, but not always, equivalent to bits per second. Compare bit rate. (2) The maximum speed at which data can be sent down a channel, such as a telephone line; often confused with the actual speed at which the data is transmitted between two computers, measured in bits per second.  
BBS: See bulletin board system.  

BBU: Abbreviation for Bob Bailey unit; a custom gate-array chip on the Macintosh SE that handles RAM, video, and sound, and that selects devices and performs other functions.  

bidirectional printing: A mode of printer operation in which characters are printed both when the print head is moving from left to right and when it is moving from right to left. Bidirectional printing is the default mode for the ImageWriter LQ. Compare unidirectional printing.  

binary: (adj.) Characterized by having two different components or by having only two alternatives or values available; sometimes used synonymously with binary system.  

Binary-Decimal Conversion Package: A Macintosh package for converting integers to decimal strings and vice versa.  

binary digit: The smallest unit of information in the binary number system; a 0 or a 1. Also called a bit.  

binary file: (1) A file whose data is to be interpreted in binary form. Machine-language programs and pictures are stored in binary files. Compare text file. (2) A file in binary file format.  

binary file format: The ProDOS 8 loadable file format, consisting of one absolute memory image along with its destination address. A file in binary file format has ProDOS file type $06 and is referred to as a BIN file. The System Loader cannot load BIN files.  

binary operator: An operator that combines two operands to produce a result. For example, + is a binary arithmetic operator; < is a binary relational operator; OR is a binary logical operator. Compare unary operator.  

binary synchronous communication (BSC): A type of protocol developed by IBM that uses synchronization of characters to control the transfer of data over communication lines. Also referred to as bi-sync communication. Compare SNA/SDLC.  

binary system: (1) A number system that uses only 0 and 1 as digits. Because computers can keep track of only two states (on or off), engineers code data in terms of 0's and 1's. (2) The representation of numbers in the base-2 system, using only the two digits 0 and 1. For example, the numbers 0, 1, 2, 3, and 4 become 0, 1, 10, 11, and 100 in binary notation. The binary system is commonly used in computers because the values 0 and 1 can easily be represented in a variety of ways, such as the presence or absence of current, positive or negative voltage, or a white or black dot on the display screen. A single binary digit-a 0 or a 1-is called a bit. Compare decimal system, hexadecimal system.  

BIN file: A file in binary file format.  

bit: A contraction of binary digit. The smallest unit of information that a computer can hold. The value of a bit (1 or 0) represents a simple two-way choice, such as yes or no, on or off, positive or negative, something or nothing. See also binary system.  

bit image: A collection of bits in memory that represents a two-dimensional surface. For example, the screen is a visible bit image.  
bitmap: (1) A set of bits that represents the graphic image of an original document in memory. (2) A set of bits that represents the positions and states of a corresponding set of items, such as pixels. In QuickDraw, a pointer to a bit image, the row width of that image, and its boundary rectangle. Used by the Macintosh to construct graphic images and fonts. Compare pixel map. See also bit image, global page bitmap, volume bitmap.  

bitmapped character: A character that exists in a computer file or in memory as a bitmap, is drawn as a pixel pattern on the graphics screen, and is sent to the printer as graphics data.  

bitmapped display: A display whose image is a representation of bits in an area of RAM called the screen buffer. With such a display, each dot, or pixel, on the screen corresponds, or is "mapped," to a bit in the screen buffer.  

bitmapped font: A font made up of bitmapped characters. Fonts stored in a Macintosh system file are bitmapped fonts, for example. Compare internal font.  

bit rate: The speed at which bits are transmitted, usually expressed as bits per second, or bps. Compare baud.  

bits per second: See bit rate.  

blank: A place to enter information. Task Info windows, dialog boxes, and tables have blanks.  

BLOAD: The binary load command; it causes the binary form of a file to be placed in memory. If the file is not a binary file, its uninterpreted image is placed in memory.  

block: (1) A unit of data storage or transfer, typically 512 bytes. In BASIC, the CATALOG command reports the sizes of disks and files in blocks. In Pascal, a block is a module of a program that includes a definition part, declaration part, and statement part. (2) A contiguous, page-aligned region of computer memory of arbitrary size, allocated by the Memory Manager. Also called a memory block.  

block device: A device that reads and writes blocks of bytes at a time. A block device can read from or write to any accessible block on demand. Disk drives are block devices. Also called block I/O device.  

block I/O: The transfer of data as chunks (blocks) of contiguous information. In A/UX, block I/O consists of 512-byte chunks by default. Compare character I/O.  

board: See printed-circuit board. 
 
board sResource list: A standard Apple sResource list that must be present in every NuBus slot card that communicates with the Macintosh II.  

body: In BASIC, the statements or instructions that make up a part of a program, such as a loop or a subroutine.  

Boolean operator: An operator, such as AND, that combines logical values to produce a logical result, such as true or false. Named for mathematician and logician George Boole. Also known as a logical operator. Compare arithmetic operator, relational operator.  

boot: Another way to say start up. A computer boots by loading a program into memory from an external storage medium such as a disk. Starting up is often accomplished by first loading a small program, which then reads a larger program into memory. The program is said to "pull itself up by its own bootstraps"-hence the term bootstrapping or booting.  

boot block: (1) An area on a formatted disk that signals the computer that the disk contains an application to be started up. (2) The first block of a file system, or the first two logical blocks of a volume. The boot block contains the system's startup instructions.  

boot device: The peripheral device that reads an operating system's initial startup instructions.  

boot disk: See startup disk.  

bootstrap: See boot.  

bottom paper-feed slot: A hole at the bottom of the ImageWriter LQ, indicated by triangular icons on either side of the printer, allowing pin-feed paper to be fed through a slotted table into the printer.  

Bourne shell: The standard UNIX System V command interpreter. See also shell.  

bps (bits per second): See bit rate.  

branch: (v.) To pass program control to a line or statement other than the next in sequence. (n.) A statement that performs the act of branching. See also conditional branch, unconditional branch.  

BREAK: A SPACE (0) signal, sent over a communication line, of long enough duration to interrupt the sender; often used to end a session with a time-sharing service. BREAK is also used in BASIC to stop execution of a program. It is generated by pressing Control-C.  

break table: A list of templates that determine the general rules for making word divisions in a particular script.  

bridge: (1) A device that lets you connect two or more networking systems together. (2) A combination of hardware and software that connects two or more networks in an internet. Bridges are used to increase the number of devices and the distances covered in a network. See also internet, zone. 
 
BRK: A "software interrupt"-an instruction that causes the 6502 or 65C02 microprocessor to halt. Pronounced "break."  

browse: (1) To wander through HyperCard's stacks. (2) To look through the information on a CD-ROM the way you page through a book or magazine waiting for something to capture your interest.  

Browse tool: The tool you use in HyperCard to click buttons and to set the insertion point in fields. Compare Button tool, Field tool.  

BRUN: The binary run command. BRUN causes a binary program to be brought into memory and run.  



BSAVE: The binary save command. BSAVE causes the binary data in a portion of memory to be saved in a disk file.  

BSC: See binary synchronous communication.  

BSD: Abbreviation for Berkeley Software Distribution; a version of the UNIX operating system developed at the University of California at Berkeley. The A/UX operating system incorporates many of the features of 4.2 BSD. 
 
buffer: (1) An area of memory set aside for the specific purpose of holding data until it is needed. (2) A "holding area" of the computer's memory where information can be stored by one program or device and then read at a different rate by another; for example, a print buffer. In editing functions, an area in memory where deleted (cut) or copied data is held. In some applications, this area is called the Clipboard. See also type-ahead buffer.  

buffer cache: A holding area in main memory where write information for block I/O is temporarily stored.  

bug: An error in a program that causes it not to work as intended. The expression reportedly comes from the early days of computing when an itinerant moth shorted a connection and caused a breakdown in a room-sized computer.  

Built-in font: See internal font. 
 
built-in shell command: A command written into the shell itself; built-in shell commands are generally used for writing shell scripts. 
 
bulletin board system (BBS): A computerized version of the bulletin boards frequently found in grocery stores-places to leave messages and to advertise things you want to buy or sell. One thing you get from a computerized bulletin board that you can't get from a cork board is free software. See also public-domain software.  

bundle: A resource (of type 'BNDL') that maps local IDs of resources to their actual resource IDs. This is used to provide mappings for file references and icon lists needed by the Finder.  

bus: (1) A path along which information is transmitted electronically within a computer. Buses connect short-distance networks of computer devices, such as processors, expansion cards, and physical RAM. Information that travels along the bus is transmitted according to a set of rules known as a protocol. (2) An electrical or electronic connection between devices. The devices connected by the bus are said to be resident on the bus and may be as small as ICs or as large as mainframe computers. A bus provides a means to send the same data, signals, or voltages (for power supply buses) to more than one device across a single carrier (wire, fiber-optic cable, and so forth). See also Apple Desktop Bus, NuBus, SE bus.  

bus lock: A mechanism for providing continuing tenure (bus ownership) by a single card. The extended tenure may include multiple transactions or attention cycles. One type of attention cycle is called a resource lock; therefore a bus lock may or may not include a resource lock.  





bus specification: The specification describing the physical characteristics of the bus and the protocol that governs the use of the bus. For example, the NuBus specification defines the clock rate of the bus, the width of the bus (in bits), the maximum rate of information transfer, and so on. It also defines the protocol, or set of rules, used to transfer information among the devices using the bus. Understanding the specification for a bus can lead to a better understanding of how the entire computer performs.  

Busy word: A firmware flag, consulted by the Scheduler, that protects system software that is not reentrant from being called while processing another call. See also reentrant, Scheduler.  

button: (1) A pushbutton-like image in dialog boxes where you click to designate, confirm, or cancel an action. Compare mouse button. (2) In HyperCard, something that initiates an action (making a connection, launching an application, starting a visual or sound effect, and so on) when you click it. See also background button, card button.  

Button tool: The tool you use in HyperCard to create, change, and select buttons. Compare Browse tool, Field tool.  

bypass: When using an AppleShare print server, to print a document from a workstation directly to a captured printer.  

byte: A unit of information consisting of a fixed number of bits. On Apple II systems, one byte consists of a series of eight bits and can take any value between 0 and 255 ($0 and $FF hexadecimal). The value can represent an instruction, number, character, or logical state. See also kilobyte, megabyte.  

byte lane: Any of four bytes that make up the NuBus data width. NuBus slot cards may use any or all of the byte lanes to communicate with each other or with the Macintosh II. See also NuBus.  
























Glossary C 

C: A portable, high-level language that also offers very low level operations, making it a flexible and efficient language for both application and system programming. A/UX is written almost entirely in C. 
 
cable: An insulated bundle of wires with connectors on the ends. Examples are serial cables, disk drive cables, and LocalTalk cables. 
 
cable extender: A small plastic adapter with a LocalTalk socket on either end that allows you to connect two LocalTalk cables together. 
 
cable terminator: See SCSI cable terminator.  

caddy: The plastic case that contains the CD-ROM while it's in use with the AppleCD SC. When you insert the caddy into the drive, the metal shutter on the caddy slides away to give the laser access to the disc surface as it spins.  

CAI: See computer-aided instruction.  

Calculator: A desk accessory that works like a four-function pocket calculator. Calculation results can be cut and pasted into your documents using the Edit menu.  

call: (n.) (1) A request from the keyboard or from a procedure to execute a named procedure. See also procedure. (2) A request issued by the CPU or a program to the SCSI card firmware. A call consists of a command number, a pointer, and a parameter list. (v.) To request the execution of a subroutine, function, or procedure.  

Cancel button: A button that appears in a dialog box. Clicking it cancels the command.  

canonical: Adhering to standard, accepted, or authoritative procedures or principles.  

canonical mode: See cooked mode.  

Caps Lock key: A key that, when engaged, causes subsequently typed letters to appear in uppercase; its effect is like that of the Shift key except that it doesn't affect numbers and other nonletter symbols. 
 
capture: When using an AppleShare print server, to take control of a printer so that it prints only documents sent by a print server, unless the Bypass option is selected. Opposite of release.  

card: (1) A printed-circuit board that plugs into one of the computer's expansion slots, allowing the computer to use one or more peripheral devices such as disk drives. (2) A printed-circuit board or card connected to the bus in parallel with other cards. Also called a peripheral card, a device, or a module. (3) HyperCard's basic entity-one screenful of information.  

card button: In HyperCard, a button that appears on a single card. The button's actions apply only to that card. Compare background button. 
 
card field: In HyperCard, a field whose size, position, text attributes, and contents are limited to the card on which the field is created. Compare background field.  

card-generic driver: A driver that can be used with a variety of NuBus cards of a given type. Compare card-specific driver.
  
card picture: In HyperCard, a picture that applies to a specific card. Compare background picture.  

card-specific driver: A driver that can be used with only one specific model of NuBus card. Compare card-generic driver.  

caret: A generic term meaning a symbol that indicates where something should be inserted in text. The specific symbol used on-screen is a vertical bar (|).  

carriage return (CR): A nonprinting ASCII character (decimal 13, hexadecimal $0D) that ordinarily causes a printer or display device to place the next character on the left margin; that is, to end a line of text and start a new one. It's used to end paragraphs. A carriage return, however, does not move the print head or cursor down to the next line; the line feed (LF) character does that. Even though you can't see carriage returns, you can delete them the same way you delete other characters. In APW C, carriage return (\r) is equal to newline (\n).  

carrier: The background signal on a communication channel that is modified to carry information. Under RS-232-C rules, the carrier signal is equivalent to a continuous MARK (1) signal; a transition to 0 then represents a start bit. 
 
carrier rod: The metal rod on which the print-head assembly rides.  

carry flag: A status bit in the microprocessor, used as an additional high-order bit with the accumulator bits in addition, subtraction, rotation, and shift operations.  

cartridge support tabs: The two plastic tabs that secure the ImageWriter ribbon cartridge to the ribbon cartridge deck.  

case sensitive: Able to distinguish between uppercase characters and lowercase characters. Programming languages are case sensitive if they require all uppercase letters, all lowercase letters, or proper use of uppercase and lowercase. For example, Applesoft BASIC recognizes only uppercase. Instant Pascal, however, is not case sensitive; you can use any combination of uppercase and lowercase letters you like.  

CAT: A ProDOS command that displays a list of the names and characteristics of all the files in a directory. This display of information is often referred to as a catalog. The CAT command displays a 40-column list.  

catalog: A list of all files stored on a disk. Synonymous with directory.  

CATALOG: A command in DOS and ProDOS that displays a list of the names and characteristics of all the files in a directory. In DOS, the CATALOG command displays a 40-column list; in ProDOS, an 80-column list.  



cathode-ray tube (CRT): An electronic device, such as a television picture tube, that produces images on a phosphor-coated screen. The phosphor coating emits light when struck by a focused beam of electrons. A CRT is a common display device used with personal computers.  

CCITT: Abbreviation for Consultative Committee on International Telegraphy and Telephony; an international committee that sets standards and makes recommendations for international communication. The CCITT interface standard is considered mandatory in Europe; it is very similar to the RS-232 standard used in the United States.  

CD: See CD-ROM, compact disc.  

CD-ROM: Acronym for compact disc read-only memory; a compact disc 120 mm (4.72 inches) in diameter that can store 550 MB of information. The information is designated as read-only memory because a CD drive can read the information but cannot record new information.  

cell: (1) The basic component of a list from a structural point of view. A cell is a box in which a list element is displayed. (2) The intersection of a row and a column in a spreadsheet. A cell can hold a number, label, function, or formula.  

central processing unit (CPU): The "brain" of the computer; the microprocessor that performs the actual computations in machine language. See also microprocessor.  

channel: A queue that's used by an application to send commands to the Sound Manager.  

char: In C, an 8-bit character data type whose range is 0 to 255. Same as unsigned char.  

character: Any symbol that has a widely understood meaning and thus can convey information. Some characters-such as letters, numbers, and punctuation-can be displayed on the monitor screen and printed on a printer. See also control character.  

character code: An integer representing the character that a key or key combination stands for.  

character device: A device that reads or writes a stream of characters, one at a time. It can neither skip characters nor go back to a previous character. Character devices include terminals, modems, keyboards, and network interfaces. Compare block device.  

character generator: The integrated circuit responsible for printing characters on the screen. Also called character generator ROM. 
 
character image: An arrangement of bits that defines a character in a font.  

character I/O: The transfer of data one character at a time rather than in blocks of characters. Compare block I/O.  






character key: (1) Any of the keys on a computer keyboard-such as letters, numbers, symbols, and punctuation marks-used to generate text or to format text; any key except Caps Lock, Command, Control, Esc, Option, and Shift. Character keys repeat when you press and hold them down. (2) A key that generates a keyboard event when pressed; that is, any key other than a modifier key.  

character limit: The maximum number of characters allowed in a single program statement. In Applesoft, the character limit is 256 (0 through 255 inclusive). Character limit is not applicable to Pascal statements.  

character offset: The horizontal separation between a character rectangle and a font rectangle; that is, the position of a given character within the font's bit image.  

character origin: The point on a base line used as a reference location for drawing a character.  

character pitch: The number of characters per inch printed along a horizontal line.  

character position: An index into an array containing text, starting at 0 for the first character.  

character set: The entire set of characters that can be either shown on a monitor or used to code computer instructions. In a printer, the entire set of characters that the printer is capable of printing.  

character string: Two or more characters read or sent in sequence; for example, Esc Z 3 Control-4 is a character string.  

character style: A set of stylistic variations, such as bold, italic, and underline. The empty set indicates plain text (no stylistic variations). 
 
character width: The distance from one character's origin to the next character's origin.  

check box: A small box associated with an option in a dialog box. When you click the check box, you may change the option or affect related options.  

checksum: The result of an arithmetic operation on the number of bits in a sequence, used to help verify the integrity of data through stages of processing.  

child process: A program submitted for execution by another program. The original program is called the parent process, and the child is created by the system call fork. See also exec.  

chip: See integrated circuit.  

choose: To pick a command by dragging through a menu. You often choose a command after you've selected something for the program to act on; for example, selecting a disk and choosing the Open command from the File menu.  





Chooser: A desk accessory that lets you configure your computer system to print on any printer for which there's a printing resource on the current startup disk. If you're part of an AppleTalk network system, you use the Chooser to connect and disconnect from the network and choose among devices connected to the network. You can also specify a user name that the system uses from time to time-when you're printing on a LaserWriter, for example.  

chr: A Pascal function. When followed by a number, chr returns the ASCII character represented by that number. For example, chr(65) is the character A.  

CHR$: An Applesoft function. When followed by a number, CHR$ returns the ASCII character represented by that number. For example, CHR$(4) returns a Control-D; CHR$(68) yields the character D.  

circuit board: A board containing embedded circuits and an attached collection of integrated circuits (chips). Sometimes called a printed-circuit board or card.  

circuitry: A network of wires, chips, resistors, and other electronic devices and connections.  

clamp: A memory location that contains the minimum and maximum excursion positions of the mouse cursor when the desktop is in use.  

class: A menu with an associated list of users.  

classic Macintosh: A term encompassing the original Macintosh (128K and 512K models), the Macintosh 512K enhanced, and the Macintosh Plus.  

clear: (1) To erase information or commands from memory. (2) To erase data from memory or reset a control register. Clearing is usually done by loading the memory location or register to be cleared with zeros.  

Clear: A command in the Edit menu that removes selected material without placing it on the Clipboard. You can use the Undo command immediately after using Clear to reverse the action.  

Clear key: A key on the numeric keypad that clears the entry in the Calculator desk accessory and in applications that require numeric entry and calculations, such as spreadsheets.  

Clear To Send: An RS-232-C signal from a DCE to a DTE that is normally kept false until the DCE makes it true, indicating that all circuits are ready to transfer data. See also Data Communication Equipment, Data Terminal Equipment.  

click: (v.) To position the pointer on something, and then press and quickly release the mouse button. (n.) The act of clicking. 
 
client: A computer that has access to services on a network. The computers that provide services are called servers. A user at a client may request file access, remote log-on, file transfer, printing, or other available services from servers.  




clip art: Electronic pictures that you can copy from one disk or document and paste into another. The term comes from using scissors to clip pictures on paper. You can buy disks of clip art and use these professional-quality drawings to illustrate your documents.  

Clipboard: The holding place for what you last cut or copied; a buffer area in memory. Information on the Clipboard can be inserted (pasted) into documents.  

clipping region: The region to which an application limits drawing within a graphics port.  

CLIST: Acronym for command list; a sequential set of commands or control statements that is assigned a name. When the CLIST name is invoked, the commands in the list are executed.  

clock chip: A special chip in which parameter RAM and the current setting for the date and time are stored. This chip is powered by a battery when the system is off, thus preserving the information.  

close: (1) To turn a window back into the icon that represents it by choosing the Close command or by clicking the close box on the left side of the window's title bar. (2) To terminate access to an open file. When a file is closed, its updated version is written to disk and all resources it needed when open (such as its I/O buffer) are released. The file must be opened before it can be accessed again.  

close box: The small white box on the left side of the title bar of an active window. Clicking it closes the window.  

closed driver: A device driver that cannot be read from or written to.  

closed file: A file without an access path. Closed files cannot be read from or written to.  

CMOS: Acronym for complementary metal oxide semiconductor; one of several methods of making integrated circuits out of silicon. CMOS devices are characterized by low power consumption. CMOS techniques are derived from MOS techniques.  

code: (1) A number or symbol used to represent some piece of information. (2) The statements or instructions that make up a program.  

code resource: A resource that contains a program's code. It is most commonly a resource of type 'CODE' (for applications and MPW tools), but other resource types such as 'DRVR' and 'PDEF' also contain code.  

code segment: (1) An individual 'CODE' resource, which is part of the code of a Macintosh application. Segments are loaded in and out of memory by the Segment Loader. (2) An object segment that contains program code. Code segments are provided for programs that differentiate between code and data segments.  

cold start: The process of starting up the computer when the power is first turned on (or as if the power had just been turned on) by loading the operating system into main memory, and then loading and running a program. Compare warm start.  


color wheel: A dialog box that appears when you click the Change Color button in the Control Panel desk accessory. The color wheel lets you adjust hue, saturation, and brightness.  

column: A vertical arrangement of graphics points or character cells on the display screen.  

command: (1) An instruction that causes a device such as a computer or printer to perform some action. A command can be typed from a keyboard, selected from a menu with a hand-held device (such as a mouse), or embedded in a program. (2) In the Standard C Library, a parameter that tells a function which of several actions to perform. (3) In the APW Shell, a word that tells APW which utility to execute. (4) An instruction that causes the target device to perform a specific operation. Commands are passed to the firmware in calls.  

command code: One or more characters whose function is to change the way a program or device acts (as opposed to text, which is simply printed).
  
command file: (1) A program that runs other programs. (2) In MPW or A/UX, a file consisting of executable commands that can be run from the shell. Also called a script. See also EXEC file.  

Command key: A key that, when held down while another key is pressed, causes a command to take effect. When held down in combination with dragging the mouse, the Command key lets you drag a window to a new location without activating it. The Command key is marked with a propeller-shaped symbol. On some machines, the Command key has both the propeller symbol and the Apple symbol on it.  

command line: The entire input string that you enter in response to the shell prompt to issue a command or to start a program. The command line includes the command itself and any arguments and flag options.  

command mode: An operating state in which a program (such as a text editor) interprets the characters you type as commands rather than as data to be entered into a file.  

command number: A hexadecimal number that corresponds to a specific ProDOS, SmartPort, or SCSI command; each command has a unique command number within its group (SCSI, ProDOS, or SmartPort).  

command register: A location in a device controller that stores control information. Compare data register.  

command structure: The nature and interrelations of all the possible instructions that can be sent to a device such as a computer or printer.  

command table: A text file containing a list of command names, command types (internal, or command; external, or utility; and language), and command or language numbers. The APW Shell checks the command table each time you execute a command. If it finds the command in the command table, it executes that command; if it doesn't find the command in the command table, the shell looks for a program with that name and attempts to run that program.  

command terminator: See end-of-command mark.  

comment: Information that is ignored by a program such as a compiler. A comment normally includes instructions, references, or notes for people inspecting a source file.  

communication controller: A type of communication control unit with its operations controlled by a program stored and executed at that unit. For example, the IBM 3704 and 3705 are communication controllers.  

communication mode: An operating state in which a serial card or port is prepared to exchange data and signals with a modem or other type of data communication equipment (DCE).  

communications protocol: See protocol.  

comp: A 64-bit SANE data type with signed integral values and one NaN.  

compact: To rearrange allocated memory blocks in order to increase the amount of contiguous unallocated (free) memory. The Memory Manager compacts memory when needed.  

compact disc: A metal-and-plastic disk in which information is stored digitally in the form of pits burned into the surface with a laser beam. Compact discs containing music are widely available, but this medium can also be used to store other kinds of data, such as text and images. See also CD-ROM.  

compaction: The process of moving allocated blocks within a heap zone to collect the free space into a single block.  

compatibility: The condition under which devices can work with each other.  

compatible: Capable of running without problems on the computer system. Applications are normally written to run on specific types of computers; applications that run on a computer system are said to be "compatible" with the computer.  

compile: To convert a program written in a high-level programming language (source code) into a file of commands in a lower-level language (object code) for later execution.  

compiler: A language translator that converts a program written in a high-level programming language (source code) into an equivalent program in some lower-level language such as machine language (object code) for later execution. Compare assembler, interpreter. 
 
component: A part; in particular, a part of a computer system.  

composite video: A video signal that includes both display information and the synchronization (and other) signals needed to display it. See also RGB monitor.  

computer: An electronic device that performs predefined (programmed) computations at high speed and with great accuracy; a machine that is used to store, transfer, and transform information.  


computer-aided instruction (CAI): The use of a computer to help teach people through interaction with educational software.  

computer language: See programming language.  

concatenate: Literally, "to chain together." (1) To combine two or more strings into a single, longer string by joining the beginning of one to the end of the other. (2) To combine two or more files.  

concurrent application: An application that runs on a file server at the same time as the AppleShare software.  

concurrent processing: The ability of an operating system to execute multiple programs simultaneously.  

conditional assembly: A feature of an assembler that allows the programmer to define macros or other pieces of code such that the assembler assembles them differently under different conditions.  

conditional branch: A branch whose execution depends on the truth of a condition or the value of an expression. Compare unconditional branch.
  
conditional compilation: In C, use of preprocessor commands (#if, #ifdef, #ifndef, #else, and #endif) to vary the output depending on compile-time conditions.  

configuration: (1) A general-purpose computer term that can refer to the way you have your computer set up. (2) The total combination of hardware components-central processing unit, video display device, keyboard, and peripheral devices-that make up a computer system. (3) The software settings that allow various hardware components of a computer system to communicate with one another.  

configuration ROM: A chip on a NuBus expansion card that contains the information the computer's microprocessor needs to communicate with the card, or with peripheral devices attached to the card.  

configure: To change software or hardware actions by changing settings. For example, you give software the necessary settings for communicating with a printer. You can configure hardware (a printer or interface card) by resetting physical elements like DIP switches or jumper blocks. Configurations can also be set or reset in software.  

connection box: A small box at one end of a LocalTalk connector. Cables plug into the box, allowing network signals to flow through it.  

connector: A plug, socket, jack, or port. See also LocalTalk connector.  

connect time: The amount of time you spend connected to an information service.  

console: (1) The main terminal (that is, keyboard and screen) of your system. The console must be connected to your system. It receives log and error messages from the operating system that are not sent to any other terminal. (2) The window where a command is entered and executed (standard input). Also, the window to which the command's output is returned (standard output).  

constant: In a program, a symbol that represents a fixed, unchanging value. Compare variable.  

content region: The area of a window that the application draws in.  

context sensitive: Able to perceive the situation in which an event occurs. For example, an application program might present help information specific to the particular task you're performing, rather than a general list of commands; such help would be context sensitive.  

continuous-form paper: See fanfold paper.  

contrast knob: A control on a monitor or other display device that lets you adjust the contrast between light and dark on the screen.  

control: (1) The order in which the statements of a program are executed. (2) An object in a window on the Macintosh screen with which the user, by using the mouse, can cause instant action with visible results or change settings to modify a future action. The control is internally represented in a control record.  

control character: A nonprinting character that controls or modifies the way information is printed or displayed. In the Apple II computer family, control characters have ASCII values between 0 and 31, and can be typed from a keyboard by holding down the Control key while pressing some other key.  

control code: (1) One or more nonprinting characters-included in a text file-whose function is to change the way a printer prints the text. For example, a program may use certain control codes to turn boldface printing on and off. See also control character. (2) A hexadecimal number that corresponds to a particular control function for an external SCSI device. 
 
control key: See modifier key.  

Control key: A specific key on Apple II-family keyboards that produces control characters when used in combination with other keys.  

controller card: A peripheral card that connects a device such as a printer or disk drive to a computer's main logic board and controls the operation of the device.  

controlling program: A program that loads and runs other programs, without itself relinquishing control. A controlling program is responsible for shutting down its subprograms and freeing their memory space when they are finished. A shell, for example, is a controlling program. Compare application program, system program.  

Control Manager: The part of the Toolbox that provides routines for creating and manipulating controls (such as buttons, check boxes, and scroll bars).  

control panel: On ImageWriter printers, the cluster of buttons and lights near the lower-right corner of the printer.  

Control Panel: A desk accessory that lets you change the speaker volume, the keyboard repeat speed and delay, mouse tracking, color display, and other features.  

control register: A special register that programs can read from and write to; similar to soft switches. The control registers are specific locations in the I/O space ($Cxxx) in bank $E0. They are accessible from bank $00 if I/O shadowing is on.  

Control-Reset: A combination keystroke on Apple II-family computers that usually causes an Applesoft BASIC program or command to stop immediately. If a program disables the Control-Reset feature, you need to turn the computer off to get the program to stop.  

control variable: See index variable.  

convergence: The correctness of aim of the red, green, and blue beams of an RGB color monitor. When the beams converge properly, the monitor gives the best quality color. You can test your monitor's convergence and adjust it by using the Control Panel desk accessory.  

conversion command: A command that allows you to convert a DOS 3.3 file structure to a ProDOS file structure and vice versa. The command also allows you to list the directory or catalog of each type of file.  

cooked input: Data that has been processed by a terminal driver's line discipline. Special characters such as the erase and kill characters cause the line discipline to convert the raw data accordingly.  

cooked mode: A terminal driver's method of operation that converts data sent from the keyboard or to the terminal screen. This conversion is performed by a line discipline to accommodate interactive use of the system. For example, an erase character sent from the keyboard causes the line discipline to delete the previous character; the terminal driver then sends the converted data to the reading process. Also known as canonical mode. Compare raw mode.  

coordinate: One of a pair of numbers that designates a position on a grid. The numbers correspond to the columns (vertical placement) and rows (horizontal placement) in a display grid.  

coordinate axis: A figure used with graphs to define the scale, consisting of a horizontal or vertical line intersected by tick marks at regular intervals.  

coordinated font: A font that is assigned to a font class and has a correctly formatted name. Compare noncoordinated font.  

coordinate plane: A two-dimensional grid. In QuickDraw, the grid coordinates are integers ranging from -32,767 to 32,767, and all grid lines are infinitely thin.  

coprocessor: An auxiliary processor that is designed to relieve the demand on the main processor by performing a few specific tasks. Coprocessors may favor a certain set of operations, like floating-point calculations for graphics instruction looping, and therefore they can optimize the speed at which such operations are processed. Generally, coprocessors handle tasks that could be performed by the main processor running appropriate software but would be performed much more slowly that way.  

copy-protect: To make a disk uncopyable. Software publishers frequently try to copy-protect their disks to prevent them from being illegally duplicated by software pirates. Compare write-protect. See also lock. 
 
courseware: Educational software.  

COUT: The firmware entry point for the Apple II character output subroutine. COUT is an I/O link-it is in RAM rather than ROM, and so it can be modified to contain the address of any presently active character output subroutine.  

COUT1: An entry point within the Apple II character output subroutine. 
 
cover page: A page generated by a workstation's application to identify a printed document.  

CPU: See central processing unit.  

CR: See carriage return.  

crash: To cease to operate unexpectedly, possibly destroying information in the process. Compare hang.  

creation date: An attribute of a ProDOS 16 file; it specifies the date on which the file was created.  

creation time: An attribute of a ProDOS 16 file; it specifies the time at which the file was created.  

crossbar: A type of drawing pointer. A crossbar is used in HyperCard, for example, for using many of the Paint tools.  

CRT: See cathode-ray tube.  

C SANE Library: A set of routines that provides extended-precision mathematical functions.  

C shell: The standard BSD command interpreter. See also shell.  

C3COUT1: The routine that COUT jumps to when the 80-column firmware is active. Also called BASICOUT.  

current: (adj.) Describes what you're using now. For example, in HyperCard the current card is the one you can see on your screen.  

current application: The application program currently loaded and running. Every application program is identified by a User ID number; the current application is defined as that application whose User ID is the present value of the USERID global variable.  

current directory: In A/UX, the last directory you moved into with the cd command; this directory is the starting reference point for all relative pathnames you enter. Also called the working directory.  

current input device: The source, such as the keyboard or a modem, from which a program is currently receiving its input.  

current language: The APW language type that is assigned to a file opened by the APW Editor. If an existing file is opened, the current language changes to match that of the file.  



current line: The data in the print buffer that is currently being processed by the printer; the printer commands in this line are read and acted on as appropriate. The current line is not printed until a print command is received or a full line's worth of text is in the print buffer. Command codes in the line following the current line in the print buffer are not read by the printer until the current line has been printed or canceled.  

current output device: The destination, such as the display screen or a printer, currently receiving a program's output.  

current prefix: The prefix that is used by the APW Shell if a partial pathname is used.  

current startup disk: The disk that contains the system files the computer is currently using. The startup disk icon always appears in the upper-right corner.  

cursor: (1) A symbol displayed on the screen marking where the user's next action will take effect or where the next character typed from the keyboard will appear. (2) A mark on the screen that indicates your position on the command line or inside a file. The cursor is usually a small box or an underscore, and it usually blinks. (3) The term used in technical manuals for the pointer on the screen.  

cut: To remove something by selecting it and choosing Cut from a menu. What you cut is placed on the Clipboard. In other editing applications, "Delete" serves the same function. See also buffer.  

cut and paste: To move something from one place in a document to another in the same document or a different one. It's the computer equivalent of using scissors to clip something and glue to paste the clipping somewhere else.  

Cut Sheet Feeder: An optional feature of the ImageWriter LQ, consisting of one, two, or three bins and a forward collator that automatically feeds and collates stationary, letterhead, and envelopes for you. It holds up to 100 sheets of paper per bin.  

cycle: One period of the NuBus clock, nominally 100 nanoseconds in duration, and beginning at the rising edge.  


















Glossary D 

DAC: See digital-to-analog converter.
  
daemon: A noninteractive process that manages services. Network daemons, for example, automatically handle incoming network connection requests.  

daisy chain: (n.) A colloquial term for a group of devices connected to a host device, where the first device in the "chain" is connected to the host, the second device is connected to the first, the third device is connected to the second, and so on.  

daisy-chain: (v.) To link together sequentially.  

daisy wheel: A printing element shaped like a daisy: characters are at the ends of "petals" radiating from a central hub. When installed in the printer, the element spins to move each letter into position as needed for printing. 
Sometimes called a print wheel.  
daisy-wheel printer: A printer that uses a daisy wheel to print characters on paper. Compare dot-matrix printer, laser printer.  

data: Information, especially information used or operated on by a program. The smallest unit of information a computer can understand is a bit.  

database: (1) A collection of information organized in a form that can be readily manipulated and sorted by a computer user. (2) Short for database management system.  

database management system: A software system for organizing, storing, retrieving, analyzing, and modifying information in a database.  

data bits: In the stream of bits being sent from your computer to a peripheral device or another computer, the bits that contain meaningful information; distinguished from bits used to indicate that a character is about to start, has stopped, or is correct. See also start bit, stop bit.  

data block: A 512-byte information portion of a ProDOS 16 standard file.  

data buffer: Heap space containing information to be written to a file or device driver from an application, or read from a file or device driver to an application.  

data bus: The path along which general information is transmitted within the computer. The wider the data bus, the more information can be transmitted at once. The Macintosh II, for example, has a 32-bit data bus. Thus, 32 bits of information can be transferred at a time, so that information is transferred twice as fast as in 16-bit computers (assuming equal system clock rates).  

data byte: The basic unit of data the computer sends to the printer.  

data byte length: The number of bits in a data byte. The ImageWriter LQ receives data in 8-bit data bytes.  



Data Carrier Detect (DCD): An RS-232-C signal from a DCE (such as a modem) to a DTE (such as an Apple IIc) indicating that a communication connection has been established. See also Data Communication Equipment, Data Terminal Equipment.  

Data Communication Equipment (DCE): As defined by the RS-232-C standard, any device that transmits or receives information. Usually this device is a modem.  

data cycle: Any period in which data is known to be valid and acknowledged. It includes ack cycles as well as intermediate data cycles within a block transfer.  

data disk: A disk that contains your work-letters, budgets, pictures, and so on-in the form of files.  

data fork: The part of a file that contains data, accessed via the File Manager.  

data format: The form in which data is stored, manipulated, or transferred. Serial data transmitted and received typically has a data format of one start bit, five to eight data bits, an optional parity bit, and one or two stop bits.  

Datagram Delivery Protocol (DDP): An AppleTalk protocol managing socket-to-socket delivery of datagrams over a networking system. 
 
data register: A location in a device controller that stores data. Compare command register.  

data segment: An object segment that consists primarily of data. Data segments are provided for programs that differentiate between code and data segments.  

data set: A device that modulates, demodulates, and controls signals transferred between business machines and communication facilities; a form of modem.  

Data Set Ready (DSR): An RS-232-C signal from a DCE to a DTE indicating that the DCE has established a connection. See also Data Communication Equipment, Data Terminal Equipment.  

Data Terminal Equipment (DTE): As defined by the RS-232-C standard, any device that generates or absorbs information, thus acting as an endpoint of a communication connection. A computer might serve as a DTE.  

Data Terminal Ready (DTR): (1) One of the handshake lines in a data transmission interface. Also, a name for the default communications protocol for the ImageWriter LQ printer. See also hardware handshake. (2) An RS-232-C signal from a DTE to a DCE indicating a readiness to transmit or receive data. See also Data Communication Equipment, Data Terminal Equipment.  

date/time record: An alternate representation of the date and time (which are stored on the clock chip in seconds since midnight, January 1, 1904).  

DCB: See Device Control Block.  

DCD: See Data Carrier Detect.  

DCE: See Data Communication Equipment.  
DDN: See Defense Data Network.  

DDP: See Datagram Delivery Protocol.  

debug: A colloquial term that means to locate and correct an error or the cause of a problem or malfunction in a computer program. Often synonymous with troubleshoot. See also bug.  

debugger: A utility that allows you to analyze a program for errors that cause it to malfunction. For example, a debugger may allow you to step through execution of the program one instruction at a time.  

decimal system: The commonly used form of number representation, in which numbers are expressed in the base-10 system, using the ten digits 0 through 9. Compare binary system, hexadecimal system.  

decimal tab: A tab, represented by a decimal tab marker, that aligns columns of numbers at the decimal point position (or columns of words to the left of the tab).  

decimal tab marker: An unfilled triangle with a dot in it that you drag from the decimal tab well to a position under the inch scale of a ruler. The decimal tab marker indicates the position to which the insertion point will move when you press Tab.  

declaration ROM: Read-only memory on a NuBus slot card that contains information about the card and may also contain code or other data.  

decrement: In programming, to decrease the value of a variable used as a counter. Compare increment.  

default: A value, action, or setting that a computer system assumes, unless the user gives an explicit instruction to the contrary. For example, unless told otherwise, the ImageWriter LQ begins printing with a left margin set to the default value of 0. Default values prevent a program from stalling or crashing if no value is supplied by the user.  

default prefix: The pathname prefix attached by ProDOS 16 to a partial pathname when no prefix number is supplied by the application. The default prefix is equivalent to prefix number 0/.  

Defense Data Network (DDN): A single, wide area, packet-switching network that integrates the ARPANET research network and the MILNET defense network.  

deferred execution: Execution of an instruction only when the complete program of which it's a part is run. In BASIC, you defer execution of an instruction by preceding it with a program line number. The complete program executes consecutive instructions in numerical order. Compare immediate execution.  

deferred printing: Writing a representation of a document's printed image to a disk or to memory, and then printing it (as opposed to immediate printing).  

DEL: See delete character.  


delete: To remove something, such as a character or word from a file, or a file from a disk. Keys such as the Backspace key and the Delete key can remove one character at a time by moving to the left. The Cut command removes selected text and places it on the Clipboard; the Clear command removes selected text without placing it on the Clipboard. (The Undo command can reverse the action of Clear and of the Backspace or Delete key if it is used immediately.)  

delete character: ASCII code $7F (DEL).
  
Delete key: A key that moves the insertion point backward, removing the previously typed character, or that removes the current selection. Its function is identical to that of the Backspace key on the original Macintosh keyboards. Compare Forward Delete key.  

delimiter: A character that is used for punctuation to mark the beginning or end of a sequence of characters and is therefore not considered part of the sequence itself. For example, Applesoft BASIC uses the double quotation mark (") as a delimiter for string constants: the string "DOG" consists of the three characters D, O, and G, and does not include the quotation marks. 
 
delta: The difference from something the program already knows. For example, mouse moves are represented as deltas compared to previous mouse locations. The name comes from the way mathematicians use the Greek letter delta (d) to represent a difference.  

delta guide: A description of something new in terms of its differences from something the reader already knows about. The name comes from the way mathematicians use the Greek letter delta (d) to represent a difference.  

demodulate: To recover the information being transmitted by a modulated signal. For example, a conventional radio receiver demodulates an incoming broadcast signal to convert it into the sound emitted by the radio's speaker. Compare modulate.  

demon: See daemon.  

demount: See unmount.  

denormalized number: A number represented in floating-point notation, in which the first bit of the significand is 0. Compare normalized number.  

dereference: In programming, to refer to a block by its master pointer (directly) instead of by its handle (indirectly).  

descent: The vertical distance from a font's base line to its descent line. 
 
descent line: A horizontal line that coincides with the bottoms of character descenders (such as the tail on a lowercase p) extending farthest below the base line. See also ascent line, base line, font size, x-height.  

deselect: A command to a device such as a printer to place it into a condition in which it will not receive data. A deselect command has an effect opposite to that of a select command.                      




desk accessory: A "mini-application" that is available from the Apple menu regardless of which application you're using-for example, the Calculator, Note Pad, Alarm Clock, Puzzle, Scrapbook, Key Caps, and Chooser. Desk accessories are files of type 'DFIL' and creator 'DMOV', and are installed by using the Font/DA Mover.  

Desk Manager: The part of the Toolbox that supports the use of desk accessories from an application.  

desk scrap: Synonymous with buffer.  

desktop: Your working environment on the computer-the menu bar and the gray area on the screen. You can have a number of documents on the desktop at the same time. At the Finder level, the desktop displays the Trash and the icons (and windows) of disks that have been accessed.  

Desktop: In AppleWorks, an area of memory where you can keep several files at a time. Once files are in the Desktop, you can switch back and forth between files without having to get files from the data disk. 
 
desktop environment: A set of program features that make user interactions with an application resemble the way people work on a desk top. Commands appear as options in pull-down menus, and material being worked on appears in areas of the screen called windows. The user selects commands or other material by using the mouse to move a pointer around on the screen or by using keyboard equivalents.  

Desktop file: A resource file in which the Finder stores the version data, bundle, icons, and file references for each application on the volume.  

desktop publishing: A system providing you with the ability to produce publication-quality documents. A Macintosh computer, a LaserWriter printer, and page-formatting software provide this capability.  

destination: (adj.) Describes the disk or folder that receives a copied or translated file, as in destination disk.  

destination volume: The duplicate volume, as opposed to the source (original) volume. When you are making a copy of a file or a volume, the destination volume is the volume onto which you are copying. Compare source volume. See also volume.  

device: (1) A hardware component of a computer system, such as a video monitor, a disk drive, or a printer. Also called a peripheral device because such equipment is often physically separate from, but attached to, the computer. (2) A part of the computer, or a piece of external equipment, that can transfer information. (3) Any piece of equipment that can be attached to a network-a computer, a printer, a file server, a print server, or any other peripheral device.  

device address: A value in the range $00 through $0F assigned to each device connected to the Apple Desktop Bus.  

Device Control Block (DCB): A block of device-specific data stored on the device itself. Data in the DCB is usually setup information for use in initializing the device after power-up or reset.  

device driver: A program that manages the transfer of information between the computer and a peripheral device. See also resource.  
device driver event: An event generated by one of the computer's device drivers.  

device file: A file that represents a device. For example, an A/UX process reading from or writing to the device file /dev/rfloppy0 is actually reading from or writing to the first floppy disk drive on the Macintosh II. Also called device special file.  

device handler: See device driver, resource.  

device handler ID: A value that identifies the kind of device connected to the Apple Desktop Bus.  

Device Information Block (DIB): A block of device-specific data stored on the device itself. Data in the DIB is used to construct the SDAT and DIBTAB for the device.  

device I/O space: An area of memory that's used for accessing hardware devices, through hardware logic internal to the device.  

Device Manager: The part of the operating system that supports device input and output.  

device name: The name used in pathnames to refer to a particular device without regard to the files associated with the device. 
 
device number: See major device number, minor device number.  

device partition: A set of blocks on a device set up for use by one or more operating systems. All the operating systems using a partition must be compatible.  

Device Partition Map (DPM): A table made up of a number of 1-block entries called Partition Descriptor Maps. The DPM always begins on physical block 1 of any device and is defined as logical block 0.  

device resource file: An extension of the printer resource file containing all the resources needed by the Chooser for operating a particular device (including the device driver code).  

device switch: A data structure composed of the addresses of routines that manage input and output for a device.  

diagnostic output: A file to which error messages are sent by default. Generally merged with standard output but can be redirected.  
dialog: See dialog box.  

dialog box: (1) A box that contains a message requesting more information from you. Sometimes the message warns you that you're asking your computer to do something it can't do or that you're about to destroy some of your information. In these cases, the message is often accompanied by a beep. (2) A box that a Macintosh application displays to request information or to report that it is waiting for a process to complete. A dialog box is internally represented in a dialog record.  

Dialog Manager: The part of the Toolbox that provides routines for implementing dialog and alert boxes.  


dialog record: The internal representation of a dialog box, where the Dialog Manager stores all the information it needs for its operations on that dialog box.  

DIB: See Device Information Block.  

DIBTAB: A software table loaded into SCSI card RAM that contains information on the type and version of the device, as well as the logical size and accessibility of the device. Often this is the same information as that contained in the DIB.  

digit: (1) One of the characters 0 through 9, used to express numbers in decimal form. (2) One of the characters used to express numbers in some other form, such as 0 and 1 in binary or 0 through 9 and A through F in hexadecimal.  

digital: Represented in a discrete (noncontinuous) form, such as numerical digits or integers. For example, contemporary digital clocks show the time as a digital display (such as 2:57) instead of using the positions of a pair of hands on a clock face. Compare analog.  

digital data: Data that can be represented by digits-that is, data that are discrete rather than continuously variable. Compare analog data.  

digital oscillator chip: An integrated circuit in the Apple IIgs that contains 32 digital oscillators, each of which can generate a sound from stored digital waveform data.  

digital signal: A signal that is sent and received in discrete intervals, rather than varying continuously over time. Compare analog signal.  

digital-to-analog converter (DAC): A device that converts quantities from digital to analog form.  

digital transmission: Transmission of a discretely variable signal as opposed to a continuously variable signal. Quantities such as temperature are continuously variable-that is, a given temperature value may fall between 2 degrees-and so are described as analog. Data characters, on the other hand, are coded in discrete, separate pulses or signal levels-either 0 or 1, on or off, and so on-and are referred to as digital. Compare analog transmission.  

dimension: The maximum size of one of the subscripts of an array.  

dimmed: Used to describe words or icons that appear in gray. For example, menu commands appear dimmed when they are unavailable; folder icons are dimmed when they are open.  

dimmed icon: An icon that represents an opened disk or folder or a disk that has been ejected. Double-clicking a dimmed disk or folder icon causes the window for the disk or folder to become the frontmost, active window. You can select and open a dimmed icon representing an ejected disk, but you cannot open the folders or documents on it unless you insert the disk.  

DIN: Acronym for Deutsche Industrie Normal, a European standards organization.  

DIN connector: A type of connector with multiple pins inside a round outer shield.  

DIP: See dual in-line package.  

DIP switch: A small switch that can be set manually for two different values (usually on or off). There are 24 switches in three DIP switch assemblies inside the case of the Apple ImageWriter LQ.  

directive: A source-file instruction to an assembler or compiler. Directives are not translated into machine-language instructions.  

directory: (1) A pictorial, alphabetical, or chronological list of the contents of a folder or a disk. (2) A file that contains a list of all the names and locations of other files stored on a disk. These other files may themselves be directories (called subdirectories). A directory is sometimes called a catalog.  

directory dialog box: A type of dialog box you use to work in the hierarchical file system from within an application. Such dialog boxes appear whenever you choose the Open or Save As commands from within an application. See also hierarchical file system.  

directory file: (1) A file that contains the names and locations of other files. Related files should be grouped together into a single directory file. Compare volume directory. (2) One of the two principal categories of ProDOS 16 files. Directory files contain specially formatted entries that give the names and disk locations of other files. Compare standard file.  

directory hierarchy: The collection of all files on the currently mounted file systems.  

directory window: The window that shows you the contents of a disk or folder.  

direct page: A page (256 bytes) of bank $00 of Apple IIgs memory, any part of which can be addressed with a short (one-byte) address because its high-order address byte is always $00 and its middle address byte is the value of the 65C816 direct register. Co-resident programs or routines can have their own direct pages at different locations. The direct page corresponds to the 6502 processor's zero page. The term direct page is often used informally to refer to any part of the lower portion of the direct-page/stack space. See also direct register, zero page.  

direct-page/stack space: A portion of bank $00 of Apple IIgs memory reserved for a program's direct page and stack. Initially, the 65C816 processor's direct register contains the base address of the space, and its stack register contains the highest address. In use, the stack grows downward from the top of the direct-page/stack space, and the lower part of the space contains direct-page data. See also direct page, direct register, stack, stack register.  

direct register: A hardware register in the 65C816 processor that specifies the start of the direct page.  

disabled: Describes a menu item or menu that cannot be chosen; the menu item or menu title appears dimmed. A disabled item in a dialog or alert box has no effect when clicked.  





disassembler: (1) A language translator that converts a machine-language program into an equivalent program in assembly language, which is easier for programmers to understand. The opposite of an assembler. (2) A program that examines data in memory and interprets it as a set of assembly-language instructions. Assuming that the data is object code, a disassembler gives the user the source code that could have generated that object code.  

disc: See compact disc.  

disk: A flat, circular, magnetic surface, serving as a medium for storing information. A RAM disk is memory that functions as a cross between internal memory (RAM) and a disk. See also CD-ROM, floppy disk, hard disk.  

disk-based: See disk-resident.  

disk buffer: An area in RAM used by the operating system as a temporary holding area before it saves the information on a disk.  

disk capacity: The maximum amount of data a disk can hold, usually measured in kilobytes (K) or megabytes (MB). For instance, Apple 3.5-inch disks typically have a disk capacity of either 400K or 800K.  

disk controller card: A peripheral card that provides the connection between one or two disk drives and the computer. This connection, or interface, is built into both the Apple IIc and the Macintosh family of computers.  

disk directory: An index of a disk's contents. It holds the names and locations of every file on its disk.  

disk drive: The device that holds a disk, retrieves information from it, and saves information to it.  

disk drive light: A light that comes on when your disk drive is loading from or storing on a disk. Sometimes called an in-use light. When the light is off, it's safe to put disks in or take disks out. When the light is on, don't remove the disk inside.  

Disk Driver: The device driver that controls data storage and retrieval on 3.5-inch disks.  

disk envelope: A removable, protective paper sleeve used when handling or storing a 5.25-inch disk. It must be removed before you insert the disk in a disk drive. Compare disk jacket.  

Disk Initialization Package: A Macintosh package for initializing and naming new disks; called by the Standard File Package.  

disk-inserted event: An event generated when the user inserts a disk in a disk drive or takes any other action that requires a volume to be mounted. 
 
disk jacket: A permanent, protective covering for a disk. A 5.25-inch disk has a flexible, paper or plastic jacket; a 3.5-inch disk has a hard plastic jacket. The disk is never removed from the jacket. Compare disk envelope.  




disk operating system (DOS): An operating system whose principal function is to manage files and communication with one or more disk drives. DOS 3.3 and ProDOS 8 are two examples of Apple II disk operating systems.  

disk-resident: (adj.) Characterizes a program that does not remain in memory; the computer retrieves all or part of the program from the disk, as needed. Sometimes called disk-based. Compare memory-resident.  

disk space: The amount of space available on a disk for storing or processing a document or an application.  

Disk II drive: An older type of disk drive made and sold by Apple Computer for use with the Apple II, II Plus, and IIe. It uses 5.25-inch disks.  

disk-use light: See in-use light.  

display: (1) A general term to describe what you see on the screen of your display device when you're using a computer; from the verb form, which means "to place into view." (2) Short for display device.  

display color: The color currently being used to draw high-resolution or low-resolution graphics on the display screen.  
display device: A device that displays information, such as a television set or video monitor.  
display rectangle: A rectangle that determines where an item is displayed within a dialog or alert box.  

display screen: The screen of the monitor; the area where you view text and pictures when using the computer. Also called simply the screen.  

dispose: To permanently deallocate a memory block. The Memory Manager disposes of a memory block by removing its master pointer. Any handle to that pointer will then be invalid. Compare purge.  

disposition: An attribute of the data set where the host components reside.  

distribution list: One or more addresses that have been combined together under one name. A distribution list sends one envelope to multiple destinations. You make distribution lists by using the Create Distribution List command in the AppleFax application.  

dithering: A technique for alternating the values of adjacent dots or pixels to create the effect of intermediate values. In printing color or displaying color on a computer screen, the technique of making adjacent dots or pixels different colors to give the illusion of a third color. For example, a printed field of alternating cyan and yellow dots appears to be green. Dithering can give the effect of shades of gray on a black-and-white display, or more colors on a color display.  

dither pattern: The matrix of threshold values used to represent gray shades in a black-and-white electronic image. 

document: Whatever you create with an application program-information you enter, modify, view, or save. See also file.  

Documenter's Workbench: A group of utilities used for formatting files to be printed on a wide variety of output devices.  

document window: The window that displays a document image or a document opened from disk.  

dormant: (adj.) Describes a program that is not being executed, but whose essential parts are all in the computer's memory. A dormant program may be quickly restarted because it does not need to be reloaded from disk.  

DOS: See disk operating system.  

DOS 3.3: A disk operating system used by the Apple II family of computers. The number 3.3 indicates the version. Disks formatted with DOS 3.3 have 16 sectors per track.  

DOS 3.2: An early Apple II disk operating system. The number 3.2 indicates the version. Disks formatted using DOS 3.2 have 13 sectors per track.  

dot column: (1) A horizontal position that can be taken by the print head. The number of dot columns on a page depends on the horizontal resolution set by the character pitch command. (2) A column of dots, as in a graphics pattern specification.  

dot-matrix printer: A printer that forms characters with patterns of dots produced by tiny striker wires. Compare daisy-wheel printer, laser printer.  

dot pitch: A measure of the distance between dots on the screen. The closer the dots, the sharper and clearer the image.  

dot space: The horizontal distance between dot centers. This distance depends on the character pitch in effect.  

double: In SANE, a 64-bit floating-point data type with IEEE double precision.  

double click: (n.) Two clicks in quick succession, interpreted as a single command. The action of a double click is different from that of a single click. For example, clicking an icon selects the icon; double-clicking an icon opens it.  

double-click: (v.) To position the pointer where you want an action to take place, and then press and release the mouse button twice in quick succession without moving the mouse.  

double-click time: The greatest interval between a mouse-up event and a mouse-down event that would qualify two mouse clicks as a double click.  

double high-resolution mode: A graphics mode that can display information using a rectangular array of 560 horizontal by 192 vertical dots for black and white and 140 horizontal by 192 vertical dots for 16 colors.  

Double Hi-Res: An Apple II high-resolution display mode, consisting of an array of points 560 wide by 192 high, with 16 available colors.  

download: To transfer files or information from one computer to another, or from a computer to a peripheral device such as a printer. A printer will download fonts if a user prints a document containing fonts that are stored on a Macintosh computer but not stored in the printer's memory.  

DPM: See Device Partition Map.  

draft printing: (1) The printing of bitmapped text in which the printer driver sends printer commands and ASCII codes to the printer, which prints using its internal fonts. Draft printing is the fastest way to print a document, but it does not reproduce on paper the appearance of the characters on the screen. Compare spool printing. (2) Printing a document immediately as it's drawn in the printing GrafPort. Also known as immediate printing.  

Draft quality: A high-speed, low-density print quality on the ImageWriter LQ. Draft mode printing is used mainly for quick printouts of documents for review or editing.  

drag: To position the pointer on something, press and hold the mouse button, move the mouse, and release the mouse button. When you release the mouse button, you either confirm a selection or move an object to a new location.  

drag region: A region in a window frame; usually the title bar. Dragging inside this region moves the window to a new location and makes it the active window unless the Command key was down.  

drive: (n.) See disk drive. (v.) For a card, to cause a bus signal line to be in a known, determinate state.  

drive number: A number used to identify a disk drive. The internal drive is number 1, the external drive is number 2, and any additional drives will have larger numbers.  

drive queue: A list of disk drives connected to the Macintosh.  

driver: (1) A program, usually in a System Folder, that lets a peripheral device and a computer send and receive files. Printer drivers control printers; a hard disk driver controls exchanges between a hard disk and a computer. (2) Synonymous with resource.  

Driver Descriptor Map (DDM): A table that contains the starting address, size, and operating-system type of all device drivers resident on the device. Each descriptor is eight bytes long, one descriptor for every driver on the device.  

driver I/O queue: A queue containing the parameter blocks of all input/output requests for one device driver.  

driver name: A sequence of up to 255 printing characters used to refer to an open device driver. Driver names always begin with a period ( . ).  

driver resource: See driver.  

driving edge: The rising edge (low to high) of the central system clock (/CLK).  

DSR: See Data Set Ready.  

DTE: See Data Terminal Equipment.  

DTR: See Data Terminal Ready.  


dual in-line package (DIP): An integrated circuit packaged in a narrow rectangular box with a row of metal pins along each side. DIP switches on the box allow you to change settings. For example, ImageWriter printer DIP switches control functions such as line feed, form length, and baud setting. 
 
duplex transmission: Simultaneous two-way, independent transmission of data between two computers or between a computer and a terminal.  

duplicate file: A backup copy of a file or document that is stored in the same folder as the AppleFax application. You create duplicate files with the Copy files button in the Envelope Contents window. Your AppleFax Station sends duplicate files when the original file is not available.  

duration: The length or persistence of a signal in time. Compare frequency.  

Dvorak keyboard: An alternate keyboard layout, which increases typing speed because the keys most often used are in the positions easiest to reach. Also known as the American Simplified Keyboard. Compare QWERTY keyboard.  

DWB: See Documenter's Workbench.  

dynamic segment: A segment that can be loaded and unloaded during execution as needed. Compare static segment.  




































Glossary E 

Easy Access: A feature of system software that assists people who have difficulty typing on the keyboard or manipulating the mouse. See also mouse keys, sticky keys.  

EBCDIC: Acronym for Extended Binary-Coded Decimal Interchange Code (pronounced "EB-si-dik"). A code used by IBM that represents each letter, number, special character, and control character as an 8-bit binary number. EBCDIC has a character set of 256 8-bit characters. Compare ASCII.  

echo: To send an input character back to the originating device for display or verification; for example, to send each character of your message back to your monitor so you know it's been sent to another computer or to a printer.  

edit: To change or modify. For example, to insert, remove, replace, or move text in a document.  

Edit menu: A menu in most mouse-based programs that lists editing commands-like Copy, Cut, and Paste.  

editor: A program that helps you create and edit information of a particular form; for example, a text editor or a graphics editor.  

edit record: A complete editing environment in TextEdit, which includes the text to be edited, the GrafPort and rectangle in which to display the text, the arrangement of the text within the rectangle, and other editing and display information.  

effective address: In machine-language programming, the address of the memory location on which a particular instruction operates, which may be arrived at by indexed addressing or some other addressing method.  

effective user ID: One of two user IDs associated by the kernel with a process. When necessary for execution, the effective user ID for a process can be changed by programs to temporarily allow different permissions. After completing the task that required the different permission, the effective user ID is set back to its original permission. Compare real user ID. See also user ID.  

e flag: One of three flag bits in the 65C816 processor that programs use to control the processor's operating modes. The setting of the e flag determines whether the processor is in native mode or emulation mode. See also m flag, x flag.  

8-bit Apple II: Another way of saying standard Apple II; that is, any Apple II with an 8-bit microprocessor (6502 or 65C02).  

8-bit microprocessor: A microprocessor that can address 65,536 memory locations directly.  





8-pin mini-circular connector: The small, round connector on the serial interface cable that plugs into the printer; the connector on the end of the AppleTalk System Connector that plugs into the Modem port on the Macintosh Plus, Macintosh SE, and Macintosh II. Also known as an 8-pin mini-DIN connector.  

80-column card: Same as 80-column text card.  

80-column display: The screen display format that can fit 80 characters in one line. The other option is 40 columns.  

80-column text card: A peripheral card that allows the Apple II, Apple II Plus, and Apple IIe to display text in 80 columns (in addition to the standard 40 columns).  

80-Column Text Card: See Apple IIe 80-Column Text Card.  

80/40-column switch: A switch that controls the maximum number of columns or characters across the screen. A television can legibly display a maximum of 40 characters across the screen, whereas a video monitor can display 80 characters.  

eject: (1) To remove a disk from a disk drive. (2) To move paper out of the printer. You can eject paper by pressing the Form Feed button or by turning the platen knob clockwise.  

electronic mail (E-mail): A message sent from one computer with a modem to another computer with a modem over phone lines.  

electronic worksheet: See spreadsheet program.  

element: (1) A member of a set or collection; specifically, one of the individual variables making up an array. (2) A string of characters, terminated by a comma or a carriage return, that can be read by using the BASIC statement INPUT. For example, INPUT A$,B$ reads two elements.  

11-pin plug: A standard plug, having a maximum of 11 connector wires (pins), used to connect various devices to the computer. Standard plugs may have fewer than the maximum number of pins. They have an elongated shape like a flattened letter "D". Compare DIN connector.  

eligible: In Apple File Exchange, a file is eligible if it can be translated with a selected translator or translators.  
E-mail: See electronic mail.  

embedded: Contained within. For example, the string 'HUMPTY DUMPTY' is said to contain an embedded space.  

empty handle: A handle that points to a NIL master pointer, signifying that the underlying relocatable block has been purged.  

emulate: To operate in a way identical to a different system. For example, the 65C816 microprocessor in the Apple IIgs can carry out all the instructions in a program originally written for an Apple II that uses a 6502 microprocessor, thus emulating the 6502.  




emulation mode: A manner of operating in which one system imitates another. For example, a Macintosh computer in emulation mode can imitate the operation of an IBM 3278 terminal. An Apple IIgs computer in emulation mode uses the 8-bit configuration of the 65C816 processor to function like a 6502 processor in all respects except clock speed.  

ending value: The value against which the index variable is tested after each pass through a loop. Used to determine when to stop repeating the loop.  

end-of-command mark: A punctuation mark used to separate commands sent to a peripheral device such as a printer or plotter. Also called a command terminator.  

end-of-file (EOF): (1) In A/UX, the position of one byte past the last byte in a file (also known as the logical end-of-file ); this is equal to the actual number of bytes in the file. If a program calls a routine that uses the physical end-of-file convention, the logical end-of-file is used instead. (2) The logical size of a ProDOS 16 file; it is the number of bytes that may be read from or written to the file. See also logical end-of-file, physical end-of-file.  

end-of-line character: Any character indicating that the preceding text constitutes a full line. When text is sent to a printer, the end-of-line character indicates that the line may now be printed.  

Enter key: A key that confirms an entry or sometimes a command. 

enum: In C, an enumerated data type of 8, 16, or 32 bits depending on the range of the enumerated literals.  

envelope: A container that holds information about fax files and Macintosh files. Your AppleFax Station sends envelopes to other fax stations. You create an envelope by selecting the New Envelope Stack from the AppleFax document window and dragging it to the Envelope View. See also fax envelope, plain envelope.  

Envelope Attachment: The attachment to the Cut Sheet Feeder that automatically feeds envelopes into the ImageWriter LQ.  

Envelope View: The display area in the AppleFax document window where you create and work with envelopes.  

environment: (1) See operating environment. (2) In SANE, the rounding direction, rounding precision, exception flags, and halt settings. (3) During program execution, the complete set of machine registers associated with a running program. Saving the environment allows a program to be restored to its original operating mode with all of its registers intact as though nothing had happened. Saving and restoring an environment is most often associated with calling system functions or processing interrupts. (4) A list of characteristics that identifies you to the system and influences and constrains your access to the system. You can modify many of these characteristics. See also environment variable.  

environment variable: A characteristic controlling your use and access of the system that is available to the current shell and all of the child processes invoked from that shell. Compare shell variable.  

EOF: See end-of-file.  

erase character: The keyboard character that, when pressed, erases the last character you typed. By default, this character is Control-H in A/UX.  

ergonomics: The science of designing work environments that allow people and things to interact efficiently and safely. Sometimes called human engineering.  

error code: A number or other symbol representing a type of error.  

error condition: The state of the hardware or program after it has detected a fault in one or more commands sent to it.  

Error light: The red light that indicates a problem with the printer, such as its being out of paper.  

error message: A message displayed or printed to tell you of an error or problem in the execution of a program or in your communication with the system. An error message is often accompanied by a beep.  

escape character: ASCII character $1B (ESC). Pressing either the Esc key or Control-[ generates an escape character.  

escape code: A sequence of characters that begins with an escape character and constitutes a complete command. Escape codes are used to control the video firmware and to send certain commands to a printer. Usually synonymous with escape sequence.  

Escape key: See Esc key.  

escape mode: An operating state of the Apple IIe and IIc entered by pressing the Esc key and certain other keys. The other keys take on special meanings for positioning the cursor and controlling the display of text on the screen.  
escape sequence: See escape code.  

Esc key: A key that generates the escape character. In many applications, pressing Esc allows you to return to a previous menu or to stop a procedure. The Esc key can be used with other keys to generate escape codes.  

Ethernet: A high-speed local area network that consists of a cable technology and a series of communication protocols. The hardware (cable) provides the physical link to connect systems together. The TCP/IP protocol allows different computers to exchange information over a network. The Ethernet specification was developed by Digital Equipment Corporation, Intel Corporation, and Xerox Corporation. Ethernet is a registered trademark of Xerox Corporation.  

Ethernet cable system: A system of high-performance coaxial cables widely used in the communications industry. Ethernet cables can be part of an AppleTalk network system.  

EtherTalk: A high-speed AppleTalk network system that uses the cables of an Ethernet network. Ethernet is a widely used communications network.   

even/odd parity check: A check that tests whether the number of 1 bits in a group of binary digits is even (even parity check) or odd (odd parity check) in data transmission.  

even parity: The use of an extra bit set to 0 or 1 as necessary to make the total number of 1 bits an even number; used as a means of error checking in data transmission. Compare MARK parity, odd parity, space parity. 
 
event: A notification to an application of some occurrence, such as an interrupt created by a keypress, that the application may want to respond to.  

event-driven: (1) Describes a kind of program that responds to user input in real time by repeatedly testing for events posted by interrupt routines. An event-driven program does nothing until it detects an event such as a click of the mouse button. (2) Describes a style of programming in which program actions are based on events generated by the user, rather than on some sort of fixed script.  

Event Manager: See Toolbox Event Manager or Operating System Event Manager.  

event mask: A parameter passed to an Event Manager routine to specify which types of events the routine should apply to.  

event queue: The Operating System Event Manager's list of pending events.  

event record: The internal representation of an event, through which your program learns all pertinent information about that event.  

Everyone: The user category to which you can assign privileges for any user with access to an AppleShare file server, whether logged on as a registered user or as a guest.  

exception: (1) An error or abnormal condition detected by the processor in the course of program execution; includes interrupts and traps. (2) A condition in the SANE environment that can cause a program halt.  

exception event: Any event interpreted by the processor as an exception to normal processing. An exception event could be a reset, an interrupt, or a trap.  

exception vector: The first 256 bytes of RAM ($00 0000 through $00 00FF) as used by the 68000 processor. These locations contain the addresses of routines that gain control whenever an exception to normal processing occurs. Exceptions include such events as a reset, an interrupt, or a trap.  

exclusive OR: A logical operator that produces a true result if one of its operands is true and the other false, and a false result if its operands are both true or both false. Sometimes written as XOR. Compare AND, NOT, OR.  

exec: A system call or a built-in shell command that loads a program file and executes it by overlaying the address space of the calling process.  
EXEC: An Applesoft BASIC command that causes input to be taken from a sequential text file rather than from the keyboard. When you use the EXEC command, you control the operation of the computer by using commands that are stored in a text file.  

EXEC file: A text file that runs other programs when it is executed by the EXEC command.  

execute: To perform the actions specified by a program command or sequence of commands.  

exit function: In C, a function that is registered with onexit for execution when the program terminates.  

expansion card: A circuit board that implements specialized functions not otherwise supported by the computer. Expansion cards are installed in expansion connectors or expansion slots.  

expansion connector: A connector inside the Macintosh SE that lets you install an expansion card to enhance the computer's performance.  

expansion slot: A narrow socket into which you can install a peripheral card. Sometimes called a peripheral slot or just slot. See also auxiliary slot.  

exponent: In scientific notation, a superscripted number denoting a power to which an immediately preceding number or value is raised. For example, in 210 (2 to the 10th power), 10 is the exponent. In computer notation, 210 is shown as 2E10, where E stands for exponent. See also scientific notation, significand.  

export: (v.) (1) To pass the value of a shell variable to a child process. (2) To make local file systems available to remote users. (n.) (1) The built-in shell command for the Korn or Bourne shell that passes the values of shell variables to child processes. See also child process, shell variable. (2) For a computer on a network using the Network File System protocols, the command that makes local file systems available to remote users.  

expression: A formula in a program that defines a calculation to be performed.  


extended: In SANE, an 80-bit floating-point data type with IEEE extended precision; used for all intermediate results.  

extended 80-column card: An interface card used in other models of the Apple II that adds 64K of memory and makes it possible for the computer to display information in 80-column format instead of the standard 40-column format.  

Extended 80-Column Text Card: See Apple IIe Extended 80-Column Text Card.  

extended SmartPort call: A SmartPort call that allows data transfer to or from anywhere in the Apple IIgs memory space. Compare standard SmartPort call.  

external command: An APW utility program that functions like an APW Shell command.  

external drive: Any disk drive attached to the computer through a port or slot; distinguished from a built-in drive in the Apple IIc and Apple IIc Plus.  

external device: See device.

external reference: (1) A reference to a symbol that is defined in another segment. External references must be to global symbols. (2) A reference to a routine or variable defined in a separate compilation or assembly. 
