Text File | 1989-03-21 | 130.1 KB | 1,747 lines | [04] ASCII Text (0x0000)
Glossary F
facsimile (fax) machine: A machine that can scan a page and then transmit the image of the page over telephone lines; a receiving fax machine prints an identical copy of the original page.
fanfold paper: Special paper that comes in one continuous sheet, perforated and folded like a fan so that it lies in a stack. Also called continuous-form paper. Compare single-sheet paper. See also pin-feed paper.
fatal error: An error serious enough that the computer must halt execution.
fax: A method of transmitting images by electronic means.
fax-distribution list: A distribution list that's made up of fax-machine addresses.
fax envelope: An envelope that has been addressed with a fax-machine address or a fax-distribution list. Fax envelopes have the word Fax written across the front. These envelopes can hold only fax files and must be sent to fax machines.
fax file: A file that contains an image of a document. The file has been formatted for facsimile transmission so you can send it to a fax machine or a computer emulating a fax machine.
fax-machine address: An address that represents a fax machine.
fax station: Either a fax machine or an AppleFax Station.
FCB: See file control block.
field: (1) A data item separated from other data by blanks, tabs, or other specific delimiters. A particular type or category of information in a database management program. (2) A specific set of data that is related. A field is always defined by its size, given in bits or bytes, and usually has a name. (3) A string of ASCII characters or a value that has a specific meaning to some program. Fields may be of fixed length, or may be separated from other fields by field delimiters. For example, each parameter in a segment header constitutes a field. (4) In a BASIC file, a string of characters preceded by a return character and terminated by a return character. A field is written to a file by each PRINT statement not terminated by a semicolon. The INPUT command reads an entire field from a file. (5) In Pascal, one discrete variable within a record. (6) In HyperCard, the place where you type regular (as opposed to Paint) text. Also, the tool you use to create a field. HyperCard has two kinds of fields: card fields and background fields.
field delimiter: A character or value that designates the start or end of a field. For example, in a BASIC file each field begins and ends with a return character.
Field tool: In HyperCard, the tool you use to create, change, and select fields. Compare Browse tool, Button tool.
file: (1) Any named, ordered collection of information stored on a disk. Application programs and operating systems on disks are examples of files. You make a file when you create text or graphics, give the material a name, and save it to disk; in this sense, file is synonymous with document. A Macintosh file consists of a data fork and a resource fork. (2) For UNIX operating systems, an array of bytes; no other structure is implied by UNIX systems as they even treat devices like files.
file-buffered: Describes a buffer style in which characters sent to an output I/O function are queued and written as a block.
file control block (FCB): (1) A data structure set up in memory by ProDOS 16 to keep track of all open files. (2) A fixed-length data structure, contained in the file-control-block buffer, where information about an access path is stored.
file descriptor: A number used to identify a file. In C, a file descriptor is returned by a create or open call.
file directory: The part of a volume that contains descriptions and locations of all the files and directories on the volume. There are two types of file directories: hierarchical file directories and flat file directories.
file directory entry: The part of a ProDOS 16 directory or subdirectory that describes and points to another file. The file so described is considered to be "in" or "under" that directory. Also called a file entry.
file handling system: The set of data structures, commands, and subroutines used to manipulate files and data stored on physical devices.
file I/O queue: A queue containing parameter blocks for all input/output requests to the File Manager.
file level: See system file level.
file management: A general term for copying files, deleting files, and other chores involving the contents of disks.
File Manager: The part of the operating system that supports file input and output.
File menu: A menu in mouse-based applications that lists commands that affect whole documents-commands like Save, Print, and Quit.
file mode: See permissions.
filename: The name that identifies a file. The maximum character length of a filename and the rules for naming a file vary under different operating systems. Compare pathname.
filename expansion: A procedure performed by the shell that derives a list of files from a single, shorthand filename containing metacharacters. Also called globbing.
file number: A reference number assigned to a specific file. The Apple IIgs loader assigns a file number to each load file in a program; the MakeLib utility program assigns a file number to each object file incorporated into a library file.
file pointer: In C, a pointer to the next byte to be read or written in a stream.
file reference: A resource (type 'FREF') that provides the Finder with file and icon information about an application.
file server: (1) A specially equipped computer that allows network users to store and share information. (2) A combination of controller software and a mass-storage device that allows computer users to share common files and applications through a network. AppleShare software, Macintosh computers, and one or more hard disks make up a file server on an AppleTalk network system.
file system: A logical device (such as a disk partition) that contains the data structures that implement all or part of the directory hierarchy.
file transfer protocol: A protocol that exchanges files with a host computer.
file type: (1) In a directory listing, the code that characterizes the contents of a file and indicates how the file may be used. (2) An attribute in a ProDOS 16 file's directory entry that characterizes the contents of the file and indicates how the file may be used. On disk, file types are stored as numbers; in a directory listing, they are often displayed as three-character mnemonic codes. (3) A four-character sequence in single quotation marks, specified when a file is created, that identifies the type of file. Examples of file types are 'TEXT', 'APPL', and 'MPST'.
FILE variable: In C, a variable containing information about a stream, including the file descriptor and buffer size, location, and style.
filing calls: Operating-system calls that manipulate files. In ProDOS 16, filing calls are subdivided into file housekeeping calls and file access calls.
filter: A utility that transforms its input in some way and writes this transformed data to the standard output. Lines submitted as input to the sort command, for example, are reordered so that the lines in the output are arranged alphabetically or numerically.
filter: A program or "mask" that alters data in accordance with specific criteria, a formula, or an algorithm.
Finder: The application that maintains the Macintosh desktop and starts up other programs at the request of the user. You use the Finder to manage documents and applications, and to get information to and from disks. You see the desktop upon starting up your computer, unless you have specified a different startup application.
Finder information: Information that the Finder provides to an application upon starting it, telling it which documents to open or print.
Find File: A desk accessory that lets you find any folder or file on a disk.
firmware: Programs stored permanently in read-only memory (ROM). Such programs (for example, the Applesoft Interpreter and the Monitor program) are built into the computer at the factory. They can be executed at any time but cannot be modified or erased from main memory. Compare hardware, software.
5.25-inch disk: A flexible plastic disk measuring 5.25 inches in diameter and having a thin, flexible paper or plastic jacket. Compare CD-ROM, hard disk, 3.5-inch disk.
fixed: Describes blocks that are not movable in memory once allocated; also called unmovable. Program segments that must not be moved are placed in fixed memory blocks. Opposite of movable.
fixed-point notation: A method of representing numbers inside the computer in which the decimal point (more correctly, the binary point) is considered to occur at a fixed position within the number. Typically, the point is considered to lie at the right end of the number so that the number is interpreted as an integer. Compare floating-point notation.
fixed-point number: A signed 32-bit quantity containing an integer part in the high-order word and a fractional part in the low-order word.
fixed-width font: A font whose characters all have the same width. For example, in Courier font the letter M is the same width as the letter I. Thus, MMMMM takes up the same space as IIIII. Same as monospaced font. Compare proportional font.
flag: A variable whose value indicates whether some condition holds or whether some event has occurred. A flag is used to control the program's actions at a later time. The value of a flag is usually 0 or 1.
flag option: An argument included on the command line that instructs a program to execute a particular deviation of the command. A flag option is usually a hyphen followed by one or more characters. For example, the -l flag option to the ls command makes this utility print extra information, such as the date a file was last saved. Flag options are sometimes referred to as keyletters.
flat file system: The file system used on 400K disks and Macintosh XL hard disks. All files are at the same directory level, even though documents or folders might appear to be inside folders. Compare hierarchical file system.
flat panel display: A display device more compact than a video monitor that can be used with the Apple IIc. A flat panel display is easy to carry.
flexible disk: See 5.25-inch disk, 3.5-inch disk.
float: In C, a 32-bit floating-point data type with IEEE single precision. Equivalent to single in SANE.
Floating-Point Arithmetic Package: A Macintosh package that supports extended-precision arithmetic according to IEEE Standard 754.
floating-point coprocessor (MC68881): A coprocessor on the Macintosh II that provides high-speed support for extended-precision arithmetic.
floating-point notation: A method of representing numbers inside the computer in which the decimal point (more correctly, the binary point) is permitted to "float" to different positions within the number. Some of the bits within the number itself are used to keep track of the point's position. Compare fixed-point notation.
floating-point unit (FPU): See 68881.
floppy disk: A disk made of flexible plastic, as opposed to a hard disk, which is made of metal. The term floppy was originally applied to disks with thin, flexible disk jackets, such as 5.25-inch disks, which were literally floppy and could be easily bent. With 3.5-inch disks, the disk itself is flexible, but the jacket is made of hard plastic. Both kinds, however, are called floppy disks. See also 5.25-inch disk, 3.5-inch disk.
flush: To update an open file (write all information in the I/O buffer to a disk) without closing it.
folder: (1) A holder of documents, applications, and even other folders on the desktop. Folders act as subdirectories, allowing you to organize information in any way you want. (2) The secondary organizing unit on the server. A folder on the server is equivalent to a ProDOS subdirectory.
font: A complete set of characters in one design, size, and style. In traditional typography usage, font may be restricted to a particular size and style or may comprise multiple sizes, or multiple sizes and styles, of a typeface design. See also bitmapped font, font family, font scaling, internal font, printer font.
font characterization table: A table of parameters in a device driver that specifies how best to adapt fonts to that device.
font class: A group of fonts that all use the same method of implementing different font styles, such as italic or bold.
Font/DA Mover: An application that allows you to add or remove fonts and desk accessories from a disk's System file or from a font or desk accessory file.
font family: A complete set of characters for one typeface design, including all styles and sizes of the characters in that font. For example, the Geneva font family includes 9-point to 36-point characters in italic, bold, outlined, and other styles.
Font file: A specific file used with the Font/DA Mover. You copy fonts to and from this file to the System file of the disk that the Font/DA Mover is on.
font height: The vertical distance from a font's ascent line to its descent line.
Font Manager: The part of the Toolbox that supports the use of various character fonts for QuickDraw when it draws text.
font name: The name, such as Geneva or Times, given to a font family to distinguish it from other font families.
font number: The number by which you identify a font to QuickDraw or the Font Manager.
font record: A data structure, derived from a font resource, that contains all the information describing a font.
font rectangle: The smallest rectangle that would enclose all the character images in a font, if the images were all superimposed over the same character origin.
font scaling: A feature that allows Macintosh computers to create all sizes of a font from one size. Scaled fonts in larger sizes are usually not as attractive as the installed font.
font script: The writing system used by the font currently designated by ThePort; hence the system that determines in what form text characters are displayed to the user.
font size: The size of a font of characters in points; equivalent to the distance between the ascent line and the descent line of one line of text. Examples of font size are 12 point and 18 point. See also base line, leading, line spacing, point, x-height.
font style: A set of stylistic variations other than size, such as italic, bold, and underline.
Font Substitution option: A feature that lets you choose whether or not the Macintosh automatically substitutes LaserWriter fonts for equivalent Macintosh fonts.
footer: An identifying line at the bottom margin of a document. A footer can appear on every page and can include text, pictures, page numbers, the date, and the time. Footers that are repeated throughout a document are called running footers or running feet. Compare header.
foreground job: A process that, while running, does not allow other activities on a terminal. The shell waits until the foreground job has finished executing before the shell returns its prompt and gives you control again of the terminal. Compare background job.
fork: (n.) (1) A system call that creates a new process. (2) One of the two parts of a Macintosh file: the data fork contains data accessed via the Macintosh File Manager, and the resource fork contains data used by the application, such as menus, fonts, and icons. (v.) To create a new process.
formal parameter: In the declaration of a procedure, the parameter that will be used to pass information into the procedure for processing. Compare actual parameter.
format: (n.) (1) The form in which information is organized or presented. (2) The general shape and appearance of a printer's output, including page size, character width and spacing, line spacing, and so on. (v.) To divide a disk into tracks and sectors where information can be stored. Blank disks must be formatted before you can save information on them for the first time; synonymous with initialize.
format block: A structure in a declaration ROM that provides a standard entry point for other structures in the ROM.
form feed: An ASCII character (decimal 12) that causes a printer or other paper-handling device to advance to the top of the next page.
Form Feed button: A button on the printer's control panel that advances a whole sheet of paper, aligning the top edge of the paper with the top-of-form mark on the paper guide.
formula: An equation. By writing formulas to defne relationships between the various numbers in your spreadsheet, you can try out different numbers, and the formulas will recalculate all the totals for you.
Fortran: Acronym for Formula Translator; a high-level programming language especially suitable for applications requiring extensive numerical calculations, such as in mathematics, engineering, and other sciences.
40-column display: The screen display format that can fit 40 characters in one line. The other option is 80-column display.
Forward Delete key: A key on the Apple Extended Keyboard that causes the character to the right of the insertion point to be deleted. The insertion point does not move: the characters to its right are "vacuumed" in toward it as each is deleted. Compare Delete key.
four-tone record: A data structure describing the tones produced by a four-tone synthesizer.
four-tone synthesizer: The part of the Sound Driver used to make simple harmonic tones, with up to four "voices" producing sound simultaneously.
FPU: See 68881.
frame: (1) The time elapsed from the start bit to the last stop bit during serial communication. (2) In the CloseView utility, a thick rectangular outline that marks off the portion of the screen that will fill the screen when you turn on magnification.
frame pointer: A pointer to the end of the local variables within a routine's stack frame, held in an address register and manipulated with the LINK and UNLK instructions.
framing error: In serial data transfer, the absence of the expected stop bit(s) at the end of a received character.
free block: A memory block containing space available for allocation.
free-form database: A database that lets you enter information in paragraph form (instead of by categories) and designate keywords that you can search for later.
free-form synthesizer: The part of the Sound Driver used to make complex music and speech.
free space: The portion of a disk that is not contained in a partition.
frequency: The number of complete cycles transmitted per second. Frequency is usually expressed in hertz (cycles per second), kilohertz (kilocycles per second), or megahertz (megacycles per second). In acoustics, frequency of vibration determines musical pitch. Compare duration.
friction feed: A paper lever setting on a printer that turns off the pin-feed mechanism and engages the rollers that drive single sheets of paper using friction between the platen and the paper.
front cover: The lid that covers the front of the ImageWriter LQ. Remove the front cover to gain access to the ribbon cartridge and DIP switches. The front cover must be firmly in place or the printer will not print.
front cover window: The clear plastic piece in the upper portion of the front cover of the ImageWriter II or ImageWriter LQ.
full duplex: A four-wire communication circuit or protocol that allows two-way data transmission between two points at the same time. Compare half duplex.
full-duplex communication: A method of data transmission where two devices transmit data simultaneously. This method allows the receiving device to echo back each character of your message as it is received.
full pathname: (1) The complete name by which a file is specified. A full pathname always begins with a slash (/), because a volume directory name always begins with a slash. Also called the absolute pathname. (2) A pathname beginning from the root directory. A full pathname is a pathname that contains embedded colons but no leading colon. Compare partial pathname.
function: (1) A built-in formula in a spreadsheet you can use to calculate an average, a square root, and the like. (2) In a programming language, an instruction that converts data from one form to another; a preprogrammed calculation that can be carried out on request from any point in a program. The CHR and CHR$ functions, for example, convert an ASCII code number into its corresponding character. Because a function takes in one or more arguments and returns a single value, it can be embedded in an expression.
function key bar: The bottom line of the FT/TSO and FT/CMS screen, which can be set up with buttons for commonly used 3278 function keys.
Fwd Del: See Forward Delete key.
Glossary G-H
game I/O connector: A 16-pin connector inside the Apple II, II Plus, and IIe, originally designed for connecting hand controls to the computer, but also used for connecting some other peripheral devices. Compare hand control connector.
garbage: A string of meaningless characters that bears no resemblance to your document. It's an indication that your computer and peripheral device are using different transmission rates or data formats.
gateway: A computer that connects two or more networks, especially those using different protocols.
GB: See gigabyte.
General tool: Any HyperCard tool that isn't a Paint tool. The General tools are Browse, Button, and Field.
GETLN: The firmware routine that a program calls to obtain an entire line of characters from the currently active input device.
gid: See group ID.
gigabyte (GB): A unit of measurement equal to 1024 (210 ) megabytes. Compare byte, kilobyte, megabyte.
global backup: The process of backing up all the files on a hard disk. Compare incremental backup.
global coordinate system: The coordinate system based on the upper-left corner of the bit image being at (0,0).
global page: Under ProDOS 8, a page (256 bytes) of data at a fixed location in memory, containing useful system information (such as a list of active devices) available to any application.
global page bitmap: A portion of the ProDOS 8 global page that keeps track of memory use in the computer. Applications under ProDOS 8 are responsible for marking and clearing parts of the bitmap that correspond to memory they have allocated or freed.
global symbol: A label in a code segment that is either the name of the segment or an entry point to it. Global symbols may be referenced by other segments. Compare local symbol.
globbing: See filename expansion.
GLU: Acronym for general logic unit; a class of custom integrated circuits used as interfaces between different parts of the computer.
go-away region: A region in a window frame. Clicking inside this region of the active window makes the window close or disappear.
GPi: Abbreviation for general purpose input; a pin that receives whatever clock signal frequency an external peripheral device sends to it, allowing the external device to control the timing and the rate of information in and out of the serial port, rather than the rate being controlled by the computer. Theoretically, this results in faster, safer data transfers, because the external peripheral device does not need to have information about the timing and phase synchronization of the clock cycles that occur in the computer.
GrafPort: (1) The data type for a graphics port. (2) A shorthand way of referring to a graphics port.
GrafPort record: A data record used by QuickDraw to establish a graphics port.
graph: A pictorial representation of data.
graphics: (1) Information presented in the form of pictures or images. (2) The display of pictures or images on a computer's display screen. Compare text.
graphics mode: A way of displaying text and graphics on the screen. In graphics mode, images are formed by patterns of dots. Compare text mode.
graphics port: A complete drawing environment in QuickDraw (data type GrafPort), including such elements as a bitmap, a character font, patterns for drawing and erasing, and other graphics characteristics. Sometimes called a GrafPort.
gray scale: Shades of gray on the screen that are created by varying the intensity of the screen's pixels, rather than by using a combination of only black and white pixels to produce shading.
grounding plug: A plug that has a third (grounding) pin for safety.
group: A named collection of one or more registered file server users. Groups are created for users who usually have common interests and share information.
Group: The user category to which you can assign access privileges for members of groups created by the AppleShare administrator. The administrator creates groups of registered users only.
group ID (gid): In A/UX, a number that indicates a group to which you belong at login time. As a member of a group, you have access to certain files and directories shared by other members of your group. Each user login name has at least one group ID associated with it.
Group 2 and Group 3 fax machines: Two different categories of fax machines that work with AppleFax. See also facsimile machine.
grow region: A window region, usually within the content region, where dragging changes the size of an active window.
guest: A user who is logged on to a server without a registered user name and password. A guest cannot own a private folder.
guest file system: A file system, other than that of ProDOS 16, whose files can be read by ProDOS 16.
half duplex: A two-wire communication circuit or protocol designed for data transmission in either direction but not both directions simultaneously. Compare full duplex.
half-duplex communication: A way of communicating between your computer and another computer or a peripheral device in which you can only send data or receive it at one time-not both. The other computer cannot echo back each character of your message as it is received.
hand control connector: A 9-pin connector on the back panel of the Apple IIe and IIc computers, used for connecting hand controls to the computer. Compare game I/O connector.
hand controls: Peripheral devices with rotating dials and push buttons. Hand controls are used with game-playing programs, but they can also be used in other applications.
handle: A pointer to a master pointer, which designates a relocatable block in the heap by double indirection. See also memory handle.
handshaking: The exchange of status information between a DCE and a DTE used to control the transfer of data between them. The status information can be the state of a signal connecting the DCE and the DTE, or it can be in the form of a character transmitted with the rest of the data. See also Data Carrier Detect, Data Set Ready, Data Terminal Ready, XOFF, XON.
hang: To cease operation because either an expected condition is not satisfied or an infinite loop is occurring. A computer that's hanging is called a hung system. Compare crash.
hard copy: Information printed on paper, as opposed to being stored on disk.
hard disk: A disk made of metal and sealed into a drive or cartridge. A hard disk can store very large amounts of information compared to 3.5-inch or 5.25-inch disks. See also compact disc.
hard disk drive: A device that holds a hard disk, retrieves information from it, and saves information to it. Hard disks made for microprocessors are permanently sealed into the drives.
hardware: Those parts of the computer that you can see and touch. The computer and the machines that attach to it: the disk drive, printer, and other peripheral devices. Compare software.
hardware handshake: A protocol that tells the computer to start or stop sending data by setting the DTR (Data Terminal Ready) line logic state. The ImageWriter LQ changes the line's state depending on the capacity of its input buffer. Also known as the Data Transfer Ready protocol. Compare XON/XOFF.
hardware overrun error: The condition that occurs when the SCC's buffer becomes full.
hardware reset: The act of resetting the printer to its default settings by turning the printer off and back on. A hardware reset clears any data in the print buffer. Compare software reset.
header: An identifying line at the top margin of a document. A header can appear on every page and can include text, pictures, page numbers, the date, and the time. Headers that are repeated throughout a document are called running headers or running heads. Compare footer.
header file: A file whose contents will be included with the source file at compile time-it contains function declarations, macros, types, and defines used by the compiler. Also called include file.
heap: The area of memory in which space is dynamically allocated and released on demand, using the Memory Manager.
heap zone: An area of memory initialized by the Memory Manager for heap allocation.
here document: Input to a shell script that is embedded inside the script itself.
hertz (Hz): The unit of frequency of vibration or oscillation, defined as the number of cycles per second. Named for the physicist Heinrich Hertz. The 6502 microprocessor used in the Apple II systems operates at a clock frequency of about 1 million hertz, or 1 megahertz (MHz). The 68000 microprocessor used in the Macintosh operates at 7.8336 MHz.
hexadecimal system: The representation of numbers in the base-16 system, using the ten digits 0 through 9 and the six letters A through F. For example, the decimal numbers 0, 1, 2, 3, 4, . . . 8, 9, 10, 11, . . . 15, 16, 17 would be shown in hexadecimal notation as 00, 01, 02, 03, 04, . . . 08, 09, 0A, 0B, . . . 0F, 10, 11. Hexadecimal numbers are easier for people to read and understand than are binary numbers, and they can be converted easily and directly to binary form. Each hexadecimal digit corresponds to a sequence of four binary digits, or bits. Hexadecimal numbers are usually preceded by a dollar sign ($). Compare binary system, decimal system.
HFS: See hierarchical file system.
hierarchical file system (HFS): A feature of system software that lets you use folders to organize documents, applications, and other folders on a disk. Folders (analogous to subdirectories) can be nested in other folders to create as many levels as you need. In a hierarchical file system, a file is specified by its pathname rather than by a single filename.
hierarchical menu: A menu in which one or more individual menu items can themselves contain a submenu.
high: For an active-low signal, synonymous with inactive, deasserted, unasserted, false, and released.
high ASCII characters: ASCII characters with decimal values of 128 to 255. Called high ASCII because their high bit (first binary digit) is set to 1 (for on) rather than 0 (for off ). Compare low ASCII characters.
high-level language: A programming language that is relatively easy for people to understand. A single statement in a high-level language typically corresponds to several instructions of machine language. High-level languages include BASIC, Pascal, Logo, Pilot, SuperPILOT, and Fortran. Compare low-level language.
highlight: To make something visually distinct. For example, when you select a block of text using MacWrite, the selected text is highlighted-it appears as light letters on a dark background, rather than dark-on-light. Highlighting is accomplished by inverting the display. See also inverse video.
high-order: (adj.) Describes the most significant part of a numerical quantity. In normal representation, the high-order bit of a binary value is in the leftmost position; likewise, the high-order byte of a binary word or longword quantity consists of the leftmost eight bits. Compare low-order.
high-order byte: The more significant half of a memory address or other two-byte quantity. In the 6502 microprocessor used in the Apple II family of computers, the low-order byte of an address is usually stored first, and the high-order byte second. In the 68000 microprocessors used in the Macintosh family, the high-order byte is stored first. Compare low-order byte.
High Sierra format: The standard proposed by a number of computer and CD-ROM companies to specify a way of organizing information on a CD-ROM. The information is laid out in files located in a series of volumes, directories, and files. The High Sierra standard makes it possible to use the same CD-ROM with different kinds of computers. Only the retrieval software needs to be geared to the computer and its operating system.
high-resolution graphics: (1) The display of graphics on a screen as a six-color array of points, 280 columns wide and 192 rows high. When a text window is in use, the visible high-resolution graphics display is 280 by 160 points. Compare low-resolution graphics. (2) For the ImageWriter LQ printer, graphics printed at a vertical resolution of 216 dots per inch. Each dot column of high-resolution graphics is represented by three bytes of data. Compare standard-resolution graphics.
high-resolution mode: A graphics mode that can display information using a rectangular array of 280 horizontal by 192 vertical dots. Compare low-resolution mode.
Hi-Res: A high-resolution display mode on the Apple II family of computers, consisting of an array of points, 280 wide by 192 high, with six colors.
hold time: In computer circuits, the amount of time a signal must remain valid after some related signal has been turned off. Compare setup time. See also valid signal.
hollow: (adj.) Sometimes used to describe a disk icon that has been opened. See dimmed.
Home card: In HyperCard, a special card that acts as a pictorial index to stacks. Choose Home from the Go menu to get to Home (or press Command-H).
home computer: A computer that is small enough and affordable enough to have in your house. (When you take a "home computer" to the office, it becomes a "productivity tool.")
home control device: A device that can regulate the temperature of your home, turn lamps on and off, or monitor smoke detectors and burglar alarms.
home directory: The directory named by your environment variable $HOME. The home directory is usually the first directory you enter upon login, as designated in the file /etc/passwd. You can tailor your environment by modifying various files in your home directory.
home row: The row of keys on the keyboard where the fingers of touch-typists rest when they aren't reaching for other keys. In the standard keyboard layout, the home row contains A, S, D, F, G, and so on. In the Dvorak keyboard layout, the home row contains what August Dvorak determined were the most frequently used keys (A, O, E, U, I, and so on).
horizontal blanking interval: The time between the display of the rightmost pixel on one line and the leftmost pixel on the next line.
host: See host computer.
host command: The command that invokes the DCA file transfer program on the host, which is required by FT/TSO and FT/CMS to transfer files.
host computer: The computer that receives information from and sends data to terminals over telecommunication lines. The computer that is in control in a data communication network. The host computer may be a mainframe computer, minicomputer, or microcomputer.
hotSpot: The point in a cursor (such as the arrow pointer) that's aligned with the mouse location.
Human Interface Guidelines: A set of software development guidelines designed by Apple Computer to support the desktop concept and to promote uniform user interfaces in Apple II and Macintosh applications. See also desktop.
HyperTalk: HyperCard's built-in script language for HyperCard users.
Hz: See hertz.
Glossary I-J
I-beam: A type of pointer shaped like the capital letter "I" and used in entering and editing text.
IC: See integrated circuit.
icon: An image that graphically represents an object, a concept, or a message. Icons on the outside of the computer can be used to show you where to plug cables, such as the disk drive icon on the back panel that marks the disk drive connector. Screen icons in mouse-based applications represent disks, documents, application programs, or other things you can select and open. A screen icon is a 32-by-32-bit image.
icon list: A resource (type 'ICN#') consisting of a list of icons.
icon number: A digit from 1 to 255 to which the Menu Manager adds 256 to get the resource ID of an icon associated with a menu item.
image: A representation of the contents of memory. A code image consists of machine-language instructions or data that may be loaded unchanged into memory.
image width: The width of a character image.
ImageWriter II/LQ LocalTalk Option: A peripheral card that enables the printer to serve up to 31 computers on an AppleTalk network system.
ImageWriter II SheetFeeder: A device that holds up to 100 sheets of paper, feeds them individually into the printer, and stacks the printed pages.
ImageWriter II 32K Memory Option: A peripheral card that gives the ImageWriter II a 32,000-character memory buffer. This memory holds documents of up to 16 to 20 pages, freeing you to work at the computer while the printer prints.
immediate execution: The execution of a program statement as soon as it is typed. In BASIC, immediate execution occurs when a line is typed without a line number. Immediate execution allows you to try out nearly every statement immediately to see how it works. Compare deferred execution.
immediate printing: See draft printing.
impact dot-matrix printer: A printer, such as the ImageWriter LQ, that forms characters with patterns of dots.
implement: To put into practical effect, as to implement a plan. For example, a language translator implements a particular language.
inactive: For an active-low signal, synonymous with high.
in-care-of address: The address of an AppleFax Station that temporarily stores an envelope before sending the envelope to its final destination.
include file: In C, a file whose contents will be included with the source file at compile time-it contains function declarations, macros, types, and #define directives used by the compiler. Also called a header file.
increment: In programming, to increase the value of a variable used as a counter. Compare decrement.
incremental backup: The process of backing up all files on a hard disk that have been created, modified, or copied onto the disk since the last global backup.
indentation marker: In MacWrite, a triangular marker that marks the position of the first word in a paragraph, to the left or the right of the left margin marker. In a new document, the indentation marker is stacked with the left margin marker.
index: (1) A number used to identify a member of a list or table by its sequential position. (2) A list or table whose entries are identified by sequential position. (3) In machine-language programming, the variable component of an indexed address, contained in an index register and added to the base address to form the effective address.
index block: A 512-byte part of a ProDOS 16 standard file that consists entirely of pointers to other parts (data blocks) of the file. See also data block, standard file.
indexed addressing: A method used in machine-language programming to specify memory addresses. See also memory location.
index register: A register in a computer processor that holds an index for use in indexed addressing. The 6502 and 65C816 microprocessors used in the Apple II family of computers have two index registers, called the X register and the Y register. The 68000 microprocessor used in Macintosh-family computers has 16 registers that can be used as index registers.
index system: Like the index in a book, a list that shows the location of all the relevant information on the disc. CD-ROM retrieval software uses the index to find the information you ask for. An index can take up as much room on a CD-ROM as the information it points to.
index variable: A variable whose value changes on each pass through a loop. Often called a control variable or loop variable.
indirect recursion: A condition in which a procedure calls a second procedure, which in turn calls the first procedure. Synonymous with mutual recursion. See also recursion.
infinite loop: A section of a program that will repeat the same sequence of actions indefinitely.
infinity: A special bit pattern produced by the Standard Apple Numerics Environment (SANE) when a mathematical calculation should result in an exact mathematical infinity, or when a calculation produces a number with magnitude too great for the intended real-number format.
information service: A large database that you can subscribe to for news, stock quotations, and other services and information. You communicate with these services through your computer equipped with a modem.
information window: The window that appears when you select an icon and choose Get Info from the File menu. It supplies information such as size, type, and date, and it includes a comment box for adding information.
initialization segment: A segment in an initial load file that is loaded and executed independently of the rest of the program. It is commonly executed first, to perform any initialization that the program may require.
initialize: (1) To set to an initial state or value in preparation for some computation. (2) To prepare a blank disk to receive information by organizing its surface into tracks and sectors; same as format.
initialized disk: A disk that has been organized into tracks and sectors by the computer and is therefore ready to store information.
initial load file: The first file of a program to be loaded into memory. It contains the program's main segment and the load file tables (Jump Table segment and Pathname segment) needed to load dynamic segments and run-time libraries.
inode: A data structure that defines a file by describing the disk layout of the file data, its permissions, and its access times.
input: (n.) Information transferred into a computer from some external source, such as the keyboard, a disk drive, or a modem. (v.) To transfer information in such a way. Compare output.
input buffer: See print buffer.
input device: A device that sends information to the microprocessor. The mouse and keyboard are the Macintosh's primary input devices. Compare output device.
input driver: A device driver that receives serial data via a serial port and transfers it to an application.
input mode: The state whereby a program (such as a text editor) accepts the characters you type as data rather than commands. Also called insert mode.
input/output (I/O): The process by which information is transferred between the computer's memory and its keyboard or peripheral devices.
input routine: A machine-language routine that performs the receiving of characters. The standard input routine reads characters from the keyboard. A different input routine might, for example, read them from an external terminal. Compare output routine.
insertion point: (1) The place in a document where something will be added, represented by a blinking vertical bar. You select the insertion point by clicking where you want to make the change in the document. (2) An empty selection range.
insert mode: See input mode.
installation: The process of adding or changing information in the System Folder or System file of a disk. For example, the Installer on the Workstation Installer disk installs AppleShare software and updates the system files.
installed font: A font in a specific size that you install in the System file of a startup disk by using installation software or the Font/DA Mover.
Installer: A utility program that lets you choose an Installation script for updating your system software or adding resources.
instruction: A unit of a machine-language or assembly-language program
corresponding to a single action for the computer's processor to perform.
instruction set: The complete range of instructions a microprocessor can interpret. Each brand of microprocessor has its own instruction set.
int: In C, a 16-bit integer data type whose range is -32,768 to 32,767.
integer: A whole number in fixed-point form. Compare real number.
Integer BASIC: A version of the BASIC programming language used by the Apple II family of computers. Integer BASIC is older than Applesoft BASIC and is capable of processing numbers in integer (fixed-point) form only. Many games are written in Integer BASIC because its instructions can be executed very quickly. Compare Applesoft BASIC. See also BASIC.
integrated circuit (IC): An electronic circuit-including components and interconnections-entirely contained in a single piece of semiconducting material, usually silicon. Often referred to as a chip.
integrated software: A group of application programs, usually on one disk, designed to share data.
intelligent card: A card containing one or more processors that can work independently from the main processor of the computer.
intelligent device: A device that contains a microprocessor and a program that allows the device to interpret data sent to it as commands that the device is to perform.
interactive: Operating by means of a dialog between a computer system and a human user.
interactive editor: A utility for entering and manipulating text while you view the text. The vi and ed editors are both interactive. Compare stream editor.
interactive program: A program that allows you to enter additional commands and data during its execution instead of making you enter all of your commands and data as flag options and arguments on the command line. The vi and mail utilities are examples of interactive programs.
interactive protocol: A protocol that lets you communicate interactively with a host computer. In this kind of protocol, part or all of the contents of the screen memory are sent to the host when you press the Return key. You do not have to communicate with the host by sending it disk files.
interface: (n.) (1) The point at which independent systems or diverse groups interact. The devices, rules, or conventions by which one component of a system communicates with another. Also, the point of communication between a person and a computer. (2) The part of a program that defines constants, variables, and data structures, rather than procedures. In C, the compile-time and run-time linkage between your program and Toolbox routines. (3) The equipment that accepts electrical signals from one part of a computer system and renders them into a form that can be used by another part. (4) Hardware or software that links the computer to a device. (v.) To convert signals from one form to another and pass them between two pieces of equipment.
interface card: A card that handles the interface (or connection) between the computer and a particular peripheral device, such as a printer, a disk drive, or a modem.
interface routine: A routine called from Pascal whose purpose is to trap to a certain ROM or library routine.
interlock: In a machine such as a printer, a safety device that prevents operation under certain conditions, such as when the cover is open.
internal command: An APW Shell command that is executed by the shell program itself, rather than by a utility program.
internal font: A font stored in the printer's internal read-only memory. An internal font is printed when the printer is in text mode (that is, not printing graphics) and receives printable ASCII characters. Also called a built-in font. Compare bitmapped font. See also printer font, screen font.
International Utilities package: A Macintosh package that gives you access to country-dependent information such as the formats for numbers, currency, dates, and times.
internet: (1) A worldwide, interconnected group of networks. Internally, the internet is composed of heterogeneous networks (such as ARPANET and CSNET) that use different message formats and protocols. Through the use of gateways that convert formats and protocols between networks, the internet appears externally as a single network, with hosts on interconnected networks appearing as interconnected hosts. (2) Any interconnected group of networks, whether or not it's on the worldwide internet; for example, an interconnected group of AppleTalk network systems. Network users in an internet can share information and network devices.
internet address: (1) An address for a computer on a network. The internet address consists of a network number and a host number that is unique for that network. (2) The AppleTalk address and network number of a socket.
interpreter: A language translator that reads a program instruction-by-instruction and immediately translates each instruction for the computer to carry out. Compare compiler, assembler.
interrupt: (1) An electronic attention-getter; a signal sent to the microprocessor that is intended to force the microprocessor to stop its current activity and accept input from the device that sent the interrupt. (2) A temporary suspension in the execution of a program that allows the computer to perform some other task, typically in response to a signal from a peripheral device or other source external to the computer. (3) An exception that's signaled to the processor by a device, to notify the processor of a change in condition of the device, such as the completion of an I/O request.
interrupt character: The keyboard character that, when pressed, interrupts execution of a program and returns you to the shell prompt. By default, Control-C is A/UX's interrupt character.
interrupt handler: A routine that services interrupts. A program, associated with a particular external device, that executes whenever that device sends an interrupt signal to the computer. The interrupt handler performs its tasks during the interrupt, then returns control to the computer so it may resume program execution.
interrupt priority level: A number identifying the importance of the interrupt. It indicates which device is interrupting and which interrupt handler should be executed.
interrupt vector: A pointer to an interrupt handler.
interrupt vector table: A table maintained in memory by ProDOS 16 that contains the addresses of all currently active (allocated) interrupt handlers.
INTERSEG record: A part of a relocation dictionary. It contains relocation information for external (intersegment) references.
inumber: The offset of a particular inode within the ilist.
in-use light: A light that comes on when your disk drive is in use; sometimes called the disk-use light. When the light is off, it's safe to put disks in and take disks out of the drive. When the light is on, don't try to eject the disk or open the disk drive door.
inverse video: The display of text on the computer's display screen in the form of dark dots on a light (or other single phosphor color) background, instead of the usual light dots on a dark background. See also highlight.
invert: To highlight by changing white pixels to black and vice versa.
I/O: See input/output.
I/O device: Input/output device. A device that transfers information into or out of a computer. See input, output, peripheral device.
I/O error message: A message you get when there's a problem with the way information is being exchanged with peripheral devices.
I/O link: A fixed location that contains the address of an input/output subroutine in the computer's Monitor program.
I/O queue: See driver I/O queue, file I/O queue.
I/O redirection: See redirection.
I/O request: A request for input from or output to a file or device driver; caused by calling a File Manager or Device Manager routine asynchronously.
IRQ: A 65C816 signal line that, when activated, causes an interrupt request to be generated.
ISO: Acronym for International Standards Organization. ISO standard 9660 is very similar, but not identical, to the High Sierra format.
item: In dialog and alert boxes, a control, icon, picture, or piece of text, each displayed inside its own display rectangle. See also menu item.
item list: A list of information about all the items in a dialog or alert box.
IWM: "Integrated Woz Machine"; the custom chip that controls the Apple 3.5-inch disk drives.
jacket: See disk jacket.
jewel case: A plastic case that protects the disc when it's not in use. When you buy a CD-ROM or an audio CD, it comes in a jewel case.
job: A process that can be stopped, restarted, and moved between foreground and background processing from the C shell.
job dialog: A dialog box that sets information about one printing job; associated with the Print command.
job number: The identification number of a process executed in background under the C shell. The job number appears next to the command name when you execute the jobs command.
journaling mechanism: A mechanism that allows a program to feed events to the Toolbox Event Manager from some source other than the user.
joystick: A peripheral device with a lever, typically used to move creatures and objects in game programs. A joystick can also be used in applications such as computer-aided design and graphics programs.
jump table: A table that contains one entry for every routine in an application or MPW tool, and is the means by which the loading and unloading of segments is implemented.
Jump Table: A table contructed in memory by the System Loader from all Jump Table segments encountered during a load. The Jump Table contains all references to dynamic segments that may be called during execution of the program.
Jump Table directory: A master list in memory, containing pointers to all segments that make up the Jump Table.
Jump Table segment: A segment in a load file that contains all references to dynamic segments that may be called during execution of that load file. The Jump Table segment is created by the linker. In memory, the loader combines all Jump Table segments it encounters into the Jump Table.
justification: The horizontal placement of lines of text relative to the edges of the rectangle in which the text is drawn.
justification gap: The number of pixels that must be added to a line of text to make it exactly fill a given measure. Called slop in the interface code.
Glossary K-L
K: See kilobyte.
Kbit: See kilobit.
Kbyte: See kilobyte.
kern: To draw part of a character so that it overlaps an adjacent character.
kernel: (1) The central part of an operating system. ProDOS 16 is the kernel of the Apple IIgs operating system. (2) A UNIX program that manages the system hardware. For example, the kernel manages files, communicates with peripherals, and handles other low-level resource management tasks.
key block: The first block in any ProDOS 16 file.
keyboard: The set of keys, similar to a typewriter keyboard, used for entering information into the computer. See also numeric keypad.
keyboard-based application: An application that accepts input only from a keyboard, as compared with a mouse-based application.
keyboard configuration: A resource that defines a particular keyboard layout by associating a character code with each key or combination of keys on the keyboard or keypad.
keyboard equivalent: The combination of the Command key and another key, used to invoke a menu item from the keyboard. Also called a Command-key equivalent.
keyboard equivalent key: A key you press in conjunction with the Command key to issue a menu command.
keyboard event: An event generated when the user presses a character key on the keyboard. A key-down event is generated when the user presses a character key; a key-up event is generated when the user releases a character key. Auto-key events are repeatedly generated when the user holds down a character key.
keyboard input connector: The connector inside Apple II-family computers by which the keyboard is connected to the computer.
keyboard shortcut: A keystroke that you can use instead of a mouse action to perform a task. For example, pressing the Command and the X keys at the same time is the same as choosing the Cut command from the Edit menu.
keyboard switch: A switch above the Apple IIc keyboard that allows you to change from the QWERTY keyboard to the Dvorak keyboard and vice versa.
Key Caps: A desk accessory that shows you the optional character set available for a given font family.
key code: An integer representing a key on the keyboard or keypad, without reference to the character that the key stands for.
key-down event: An event generated when the user presses a character key on the keyboard or keypad. Compare key-up event.
KEYIN: The firmware entry point that a program uses to obtain a keystroke from the currently active input device (normally the keyboard).
keyletter: See flag option.
key script: The system that determines the keyboard layout and input method for the user interface. It may be different from the font script, which determines how text is displayed.
keystroke: A key or key combination that you assign to a macro. When pressed, it triggers the playing of the macro's script.
key-up event: An event generated when the user releases a character key on the keyboard or keypad. Compare key-down event.
keyword: (1) A word that is likely to appear in the file you're trying to find. (2) A special word or sequence of characters that identifies a particular type of statement or command, such as RUN, BRUN, or PRINT.
keyword search: A method of locating information on a CD-ROM. You type the word and the retrieval software searches for that word or derivatives of it.
kHz: See kilohertz.
kilobit (Kbit): A unit of measurement, 1024 bits, commonly used in specifying the capacity of memory integrated circuits. Not to be confused with kilobyte.
kilobyte (K): A unit of measurement consisting of 1024 (210) bytes. Thus, 64K memory equals 65,536 bytes. The abbreviation K can also stand for the number 1024, in which case Kbyte is used for kilobyte. See also megabyte.
kilohertz (kHz): A unit of measurement of frequency, equal to 1000 hertz. See also megahertz.
kind: See segment kind.
Korn shell: A command interpreter that combines many of the best features found in the standard System V shell (the Bourne shell) and the standard BSD shell (the C shell). See also shell.
KSW: Abbreviation for keyboard switch; the symbolic name of the location in the computer's memory where the standard input link (namely, to the keyboard) is stored.
LAN: See local area network.
land: The area between pits on a CD-ROM track. See also optical storage, pit.
language: See programming language.
language card: Memory with addresses between $D000 and $FFFF on any Apple II-family computer. It includes two RAM banks in the $Dxxx space, called bank-switched memory. The language card was originally a peripheral card for slot 0 of the 48K Apple II or Apple II Plus that expanded memory capacity to 64K and provided space for an additional dialect of BASIC. The langauge card was also necessary for these machines to use ProDOS.
language command: A command that changes the APW current language.
language translator: A system program that reads another program written in a particular programming language and either executes it directly or converts it into some other language (such as machine language) for later execution. See also assembler, compiler, interpreter.
laser: An acronym for light amplification by simulated emission of radiation. A device that produces an intense source of light that can be focused to a tiny spot.
laser printer: A printer that uses laser light to transfer a page image (sent by a computer) onto an electrostatically charged, light-sensitive drum. A black powder called toner adheres to the areas of the drum where the laser has drawn the image. Paper then passes over the drum, picking up the toner, and the toner is heat-fused to the paper as it rolls out of the printer. The Apple LaserWriter and LaserWriter Plus are examples of laser printers. Compare daisy-wheel printer, dot-matrix printer.
LaserWriter Namer: An application on the LaserWriter Installation Disk that you use to name and rename LaserWriter printers.
last-opened location: The last location whose value you inquired about through the Monitor.
layer: In HyperCard, the order of a button or field relative to other buttons or fields on the same card and background. The object created most recently is ordinarily the topmost object (that is, on the front layer).
leading: Pronounced "LED-ing"; the amount of blank vertical space between the descent line of one line of text and the ascent line of the next line of single-spaced text. In early typesetting, strips of lead were placed between lines of type for spacing, hence the term. Compare line spacing.
leading zero: A zero occurring at the beginning of a number, as when a number must be sent to the printer as a certain number of digits. For example, 20 can be written as a three-digit number with one leading zero: 020.
leafname: A partial pathname that contains no colons. See also pathname.
least significant bit: The binary digit in a number or data byte that contributes the smallest quantity to the value of the number; usually written at the right end of the number. Compare most significant bit.
Letter Quality: A high-density print quality on the ImageWriter LQ.
level: See system file level.
lever: The little flag-like indicator that appears to the right of the time when you choose the Alarm Clock desk accessory. When you click the lever, two panels appear that let you set the time, the date, and the alarm.
library: A collection of related functions or declarations available to a program for linking at compile time.
library dictionary segment: The first segment of a library file; it contains a list of all the symbols in the file, together with their locations in the file. The linker uses the library dictionary segment to find the segments it needs.
library file: An object file containing program segments, each of which can be used in any number of programs. The linker can search through the library file for segments that have been referenced in the program source file.
ligature: A character that combines two letters. For example, the letters f and i are sometimes combined into a ligature: f.
line: See program line.
line break: The end of a line of text on the screen or on a printed page. You can force a line break by pressing Return, or you can let an application break lines for you.
line-buffered: Describes a buffer style in which each line of output is queued for writing as soon as a newline character is written.
line editor: A utility for entering and manipulating text. The commands to add or change text are entered from a command prompt; they operate only on the lines you specify, and you cannot always see the results of your changes right away. The ed and ex utilities in A/UX are line editors. Compare screen editor.
line feed (LF): (1) An ASCII character (hex $0A) that instructs a printer or video display to advance to the next line. (2) A vertical motion of the platen, moving the paper up or down one print line.
Line Feed button: A button on the control panel of a printer that advances paper one line at a time.
line feed pitch: The number of lines printed per vertical inch.
line kill character: The keyboard character that, when pressed, erases the current command line from the shell. After you press the line kill character, the cursor moves to a new line, and you can enter a new command. Control-U is A/UX's default line kill character.
line length: The number of characters that fit in a line on the screen or on a page.
line number: A number identifying a program line in an Applesoft BASIC program.
line spacing: The vertical distance between two lines of type measured from base line to base line. For example, "10/12" indicates 10-point type with 12 points base-to-base (that is, with 2 points leading). Compare leading. See also base line, point.
link: (v.) (1) In programming, to collect one or more routines into an executable program. Also, to connect programs compiled or assembled at separate times so that they can be executed together. See also compiler. (2) To give an alternative name to a file. Compare unlink. (n.) An area in memory that contains an address and a jump instruction to a subroutine. Programs are written to jump to the link address; other programs can modify this address to substitute their own subroutines. COUT and KEYIN are examples of I/O links.
LinkEd: A command language that can be used to control the APW Linker.
linker: A program that combines files generated by compilers and assemblers, resolves all symbolic references, and generates a file that can be loaded into memory and executed.
link map: A listing, produced by the linker, that gives the name, length, and starting location of each segment in a load file.
liquid crystal display: See flat panel display.
Lisa: A model of Apple computer; the first computer that offered windows and the use of a mouse to choose commands. The Lisa was later known as the Macintosh XL.
list: To display on a monitor, or print on a printer, the contents of memory or of a file.
List Manager: The part of the Operating System that provides routines for creating, displaying, and manipulating lists.
list record: The internal representation of a list, where the List Manager stores all the information it requires for its operations on that list.
load: To transfer information from a peripheral storage medium (such as a disk) into main memory for use; for example, to transfer a program into memory for execution.
LOAD: An Applesoft BASIC command that clears the current program and variables from memory and brings a new program into memory from a file.
loader: A program that brings files from a disk into the computer's memory.
load file: The output of the linker. Load files contain memory images that the System Loader can load into memory, together with relocation dictionaries that the loader uses to relocate references.
load segment: (1) A segment in a load file. Any number of object segments can go into the same load segment. (2) In C, a part of a load file corresponding to one or more functions. Object segments are assigned to load segments at compile time by means of the #overlay preprocessor directive or at link time by LinkEd commands. Compare object segment.
local: (adj.) Nearby. Capable of direct connection using wires only, as opposed to remote, in which case communication devices are necessary.
local area network(LAN): A group of computers connected for the purpose of sharing resources. The computers on a local area network are typically joined by a single transmission cable and are located within a small area such as a single building or section of a building.
local coordinate system: The coordinate system local to a GrafPort, imposed by the boundary rectangle defined in its bit map.
localization: The process of adapting an application to different languages, including converting its user interface to a different script.
local symbol: A label defined only within an individual segment. Other segments cannot access the label. Compare global symbol.
local system: The computer from which a user originates a network command. Compare remote system.
local system administration: Management of a single computer. This includes such functions as starting up and shutting down the system, adding and removing user accounts, and backing up and restoring data. Compare network administration.
LocalTalk cable system: A system of cables, cable extenders, and connector boxes that connect computers and network devices as part of the AppleTalk network system.
LocalTalk connector: A piece of equipment consisting of a connection box, a short cable, and a machine-specific connector, that enables an Apple computer to be part of an AppleTalk network system. Also called a LocalTalk connector box.
LocalTalk Option Card: An interface card that enables a printer to serve as many as 31 computers on an AppleTalk network system.
location: See memory location.
lock: (1) To prevent documents, files, or entire disks from being altered. Files can be locked with software commands; for example, to lock a document select it and choose Get Info from the File menu, then click the Locked check box in the upper-right corner of the Info window. An entire disk can be physically locked by sliding the small tab on the back of the plastic case of a 3.5-inch disk, or by using a write-protect tab on the disk jacket of a 5.25-inch disk; in this sense lock is synonymous with write-protect. Compare unlock. (2) To prevent a memory block from being moved or purged. A block may be locked or unlocked by the Memory Manager, or by an application through a call to the System Loader. (3) To temporarily prevent a relocatable block from being moved during heap compaction.
locked file: A file whose data cannot be changed.
locked volume: A volume whose data cannot be changed. Volumes can be locked by either a software flag or a hardware setting.
logic: (1) In microcomputers, a mathematical treatment of formal logic using a set of symbols to represent quantities and relationships that can be translated into switching circuits, or gates. AND, OR, and NOT are examples of logical gates. Each gate has two states, open or closed, allowing the application of binary numbers for solving problems. (2) The systematic scheme that defines the interactions of signals in the design of an automatic data processing system.
logical block: (1) Volume space composed of 512 consecutive bytes of standard information and an additional number of bytes of information specific to the Disk Driver. (2) A block on a device that can be used by software to store data. Logical blocks on a device are numbered consecutively from 0, but may not directly correspond to their physical block number because of block sparing conducted during initialization of the device. Compare physical block.
logical disk: A disk partition that is treated by the operating system as a separate disk. See also partition.
logical element: The smallest building block in a computer system that operators can still represent symbolically. The AND gate (switch) is a logical element.
logical end-of-file: The position of one byte past the last byte in a file; equal to the actual number of bytes in the file. Compare physical end-of-file.
logical name: The name of a block, file, table, device, or other entity in software that may or may not correspond to its physical name. Compare physical name.
logical operator: An operator, such as AND, that combines logical values to produce a logical result, such as true or false; sometimes called a Boolean operator. Compare arithmetic operator, relational operator.
logic board: See main logic board.
log in: To identify yourself to the system by entering the login name of your account and your account password. Synonymous with log on; opposite of log off.
login name: In UNIX systems, the name of a user's account. Used for identification purposes.
login prompt: The prompt (usually login: on UNIX systems) by which a system tells you it is ready to accept your login name.
login shell: The shell that automatically runs after you successfully log in. See also shell.
Logo: A computer language that encourages learning through discovery. Logo is easy and fun to learn, but powerful enough for application programming. Logo's main feature is turtle graphics; a triangular shape on the screen, called a "turtle," acts as a pen to draw lines and patterns according to Logo instructions the user creates.
log off: To indicate to a system or network that you have completed your work and are terminating interaction.
log on: To identify yourself to a system or network and start to use it. Usually logging on requires a password, depending on the system. Same as log in; opposite of log off.
long: In C, a 32-bit integer data type. Its range is -2,147,483,648 to 2,147,483,647.
longword: A double-length word. For the Apple IIgs, a longword is 32 bits (4 bytes) long. In 68000 terminology (including the 68020), a longword is two 16-bit words.
loop: A section of a program that is executed repeatedly until a limit or condition is met, such as an index variable's reaching a specified ending value. See loop.
loop variable: See index variable.
Lo-Res: The lowest-resolution graphics mode on the Apple II family of computers, consisting of an array of blocks 48 rows high by 40 columns wide, with 16 available colors.
low: For an active-low signal, synonymous with active and asserted.
low ASCII characters: Characters with decimal equivalents between 0 and 127, inclusive. Called low ASCII because the high bit (leftmost binary digit) is set to 0 rather than 1. The low ASCII characters make up the standard ASCII character set. Compare high ASCII characters.
low-level language: A programming language that is relatively close to the form the computer's processor can execute directly. One statement in a low-level language corresponds to a single machine-language instruction. Examples are 6502 machine language, 6502 assembly language, and 68000 machine and assembly languages. Compare high-level language.
low-order: (adj.) Describes the least significant part of a numerical quantity. In normal representation, the low-order bit of a binary number is in the rightmost position; likewise, the low-order byte of a binary word or longword quantity consists of the rightmost eight bits. Compare high-order.
low-order byte: The less significant half of a memory address or other two-byte quantity. In the 6502 microprocessor used in the Apple II family of computers, the low-order byte of an address is usually stored first, and the high-order byte second. The opposite is true for Macintosh computers. Compare high-order byte.
low-power Schottky (LS): A type of transistor-transistor logic (TTL) integrated circuit having lower power and higher speed than a conventional TTL integrated circuit; named for Walter Schottky (1886-1956), a semiconductor physicist.
low-resolution graphics: The display of graphics on a display screen as a 16-color array of blocks, 40 columns wide and 48 rows high. For example, on a Macintosh when the text window is in use, the visible low-resolution graphics display is 40 by 40 plotting points-that is, 40 by 40 pixels. Compare high-resolution graphics. Compare high-resolution mode.
low-resolution mode: A graphics mode that can display information using a rectangular array of 40 horizontal by 48 vertical blocks. Compare high-resolution mode.
lp system: A collection of programs and files that are used to manage printer operations. These include the print spooler and a series of maintenance commands.
LQ: Letter Quality; one of the character fonts available on the ImageWriter LQ.
LQ (letter-quality) fonts: Times, Helvetica, Courier, and Symbol fonts in very large sizes. Your Macintosh uses the LQ fonts to produce high-quality output when sending fax files to fax machines.
LS: See low-power Schottky.
Glossary M
MacBinary: The default file transfer type used by FT/TSO and FT/CMS (labeled MACBIN in the setup screens).
machine language: The form in which instructions to a computer are stored in memory for direct execution by the computer's processor. Each model of computer processor (such as the 6502 microprocessor or the 68000 microprocessor) has its own form of machine language. See also assembly language.
Macintosh: A family of Apple computers, including the Macintosh 128K, Macintosh 512K, Macintosh 512K enhanced, Macintosh Plus, Macintosh SE, and Macintosh II. Macintosh computers have high-resolution screens and use mouse devices for choosing commands and for drawing pictures.
Macintosh Operating System: The combination of ROM-based and disk-based routines that together perform basic tasks such as starting the computer, moving data to and from disks and peripheral devices, and managing memory space in RAM.
Macintosh Programmer's Workshop (MPW): Apple's software development environment for the Macintosh family.
Macintosh User Interface: The standard conventions for interacting with Macintosh computers. The interface ensures users a consistent means of interacting with all Macintosh computers and the applications designed to run on them.
MacPaint document: A document created by the Macintosh MacPaint application, or any application that creates MacPaint-compatible graphics.
macro: (1) A user-defined command that tells an application to carry out a series of commands when you type the macro. (2) A recorded sequence of characters and commands, identified by a name and possibly triggered by a keystroke. Using MacroMaker, you can call upon a macro to play while you're working in an application. See also script. (3) A single keystroke or command that a program replaces with several keystrokes or commands. For example, the APW Editor allows you to define macros that execute several editor keystroke commands; the APW Assembler allows you to define macros that execute instructions and directives. Macros are almost like higher-level instructions, making assembly-language programs easier to write and complex keystrokes easier to execute.
macro assembler: A type of assembler that allows the programmer to define sequences of several assembly-language instructions as single pseudo-instructions called macros.
macro call: A request to execute a macro.
macro header: In an APW macro definition, the directive MACRO.
macro model statement: The line in an APW macro immediately following a MACRO directive.
magnitude: The vertical distance between any given point on a wave and the horizontal line about which the wave oscillates.
mail-merge application: An application that takes names and addresses from a database and puts them into form letters.
main: The name of the function that is the entry point for every C program.
main event loop: In a standard Macintosh application program, a loop that repeatedly calls the Toolbox Event Manager to get events and then responds to them as appropriate.
mainframe computer: A central processing unit or computer that is larger and more powerful than a minicomputer or a personal computer (microcomputer). Frequently called mainframe for short.
main logic board: A large circuit board that holds RAM, ROM, the microprocessor, custom-integrated circuits, and other components that make the computer a computer.
main memory: The part of a computer's memory whose contents are directly accessible to the microprocessor; usually synonymous with random-access memory (RAM). Programs are loaded into main memory, where the computer keeps information while you're working. Sometimes simply called memory. See also random-access memory, read-only memory, read-write memory.
main menu: The top level of options in a program having several levels of options. Making a choice from a main menu takes you to another menu.
main segment: The first static segment (other than initialization segments) in the initial load file of a program. It is loaded at startup and never removed from memory until the program terminates.
main unit: The computer "box," which contains the processor, memory, the built-in disk drive(s), the optional internal hard disk, and, on the Macintosh Plus and SE, the screen.
major device number: One of two numbers contained in the inode for a device. The major device number identifies the class of device (such as terminal or disk). Compare minor device number.
Make Changes: The AppleShare file server access privilege that gives the right to make changes to a folder's contents.
makefile: A file containing a collection of operations used by the make utility to construct related files.
MakeLib utility: A program that creates library files from object files.
manager: A set of data structures and routines that perform a set of related Toolbox or Operating System functions. For instance, the Window Manager handles the display and manipulation of windows on the screen.
manager workstation: A specially equipped workstation that is used to run the AppleShare menu management program.
margin marker: In MacWrite, a black triangle on each side of a ruler that you can move to mark the left or right margin of text. In a new document, the left margin marker is stacked, or aligned, with the indentation marker.
Mark: The current position in an open file. It is the point in the file at which the next read or write operation will occur.
MARK parity: A method of error checking in data transmission in which the most significant bit of every byte is set to 1. The receiving device checks for errors by looking for this value on each character. Compare even parity, odd parity, space parity.
master: (1) A card that initiates the addressing of another card or the central processor on the main logic board. The card addressed is at that time acting as a slave. (2) The glass model that is used to make the metal molds for mass-producing compact discs.
master index block: The key block in a ProDOS 16 tree file, the largest organization of a standard file that ProDOS 16 can support. The master index block consists solely of pointers to one or more index blocks. See also standard file, tree file.
master pointer: A single pointer to a relocatable block, maintained by the Memory Manager and updated whenever the block is moved, purged, or reallocated. Each allocated memory block has a master pointer, but the block is normally accessed through its memory handle (which points to the master pointer), rather than through the master pointer itself.
megabit (Mbit): A unit of measurement equal to 1,048,576 (216) bits, or 1024 kilobits, commonly used in specifying the capacity of memory ICs. Not to be confused with megabyte.
megabyte (MB): A unit of measurement equal to 1024 kilobytes, or 1,048,576 bytes. See also kilobyte.
megahertz (MHz): One million hertz. See also kilohertz.
Mega II: A custom large-scale integrated circuit that incorporates most of the timing and control circuits of the standard Apple II. It addresses 128K of RAM organized as 64K main and auxiliary banks and provides the standard Apple II video display modes, both text (40-column and 80-column) and graphics (Lo-Res, Hi-Res, and Double Hi-Res).
memory: A hardware component of a computer system that can store information for later retrieval. See also main memory, random-access memory, read-only memory, read-write memory.
memory block: A contiguous, page-aligned region of computer memory of arbitrary size, allocated by the Memory Manager. Sometimes simply called a block.
memory expansion card: A circuit board that adds extra random-access memory (RAM) to your computer; the card comes with 256K of RAM but can be expanded to 512K, 768K, or 1 megabyte. Also known as a RAM disk. Like a disk, it must be formatted with a particular disk operating system to store data. Unlike a disk, it acts like the random-access memory inside the computer, so that any data or program you put on the card can be read and used almost immediately, without making you wait while data comes in from a disk in an external disk drive.
memory handle: The identifying number of a particular block of memory. It is a pointer to the master pointer to the memory block. A handle rather than a simple pointer is needed to reference a movable memory block.
memory image: A portion of a disk file or segment that can be read directly into memory.
memory location: A unit of main memory that is identified by an address and can hold a single item of information of a fixed size. In the Apple II family of computers, a memory location holds one byte, or eight bits, of information.
Memory Manager: (1) A program in the Apple IIgs Toolbox that manages memory use. The Memory Manager keeps track of how much memory is available and allocates memory blocks to hold program segments or data. (2) The part of the Macintosh Operating System that dynamically allocates and releases memory space in the heap.
memory-mapped I/O: The method used for input and output operations in Apple II computers. Certain memory locations are attached to I/O devices, and I/O operations are just memory load and store instructions.
memory-resident: (adj.) (1) Stored permanently in memory as firmware (ROM). (2) Held continually in memory even while not in use. For example, DOS is a memory-resident program. Compare disk-resident.
Memory Segment Table: A linked list in memory, created by the loader, that allows the loader to keep track of the segments that have been loaded into memory.
menu: A list of choices presented by a program, from which you can select an action. In the desktop interface, menus appear when you point to and press menu titles in the menu bar. Dragging through the menu and releasing the mouse button while a command is highlighted chooses that command.
menu bar: The horizontal strip at the top of the screen that contains menu titles.
menu definition procedure: A procedure called by the Menu Manager when it needs to perform type-dependent operations on a particular menu (for example, when it needs to draw the menu).
menu item: A choice in a menu, usually a command to the current application. See also item.
Menu Manager: The part of the Toolbox that deals with setting up menus and letting the user choose from them.
menu record: The internal representation of a menu, where the Menu Manager stores all the information it needs for its operations on that menu.
menu title: A word, phrase, or icon in the menu bar that designates one menu. Pressing on the menu title causes the title to be highlighted and its menu to appear below it.
message: A command you send to HyperCard through a script or through the Message box. Some examples of HyperTalk messages are Go, Show, Hide, Pop Card, and Push Card.
message list: An argument that allows you to specify a group of mail messages by number or name to various mailx commands.
messages: A group of system calls that allow processes to communicate by sending formatted data streams to each other.
metacharacter: A character interpreted by a program as standing for other characters or as designating a special function. For example, the ampersand (&) metacharacter at the end of a command line causes the shell to run the command as a background job.
m flag: One of three flag bits in the 65C816 processor that programs use to control the processor's operating modes. In native mode, the setting of the m flag determines whether the accumulator is 8 bits wide or 16 bits wide. See also e flag, x flag.
MHz: See megahertz.
microcomputer: A computer, such as any of the Apple II or Macintosh computers, whose processor is a microprocessor.
microprocessor: An integrated circuit on the computer's main circuit board. The microprocessor carries out software instructions by directing the flow of electrical impulses through the computer. The microprocessor is the central processing unit (CPU) of the microcomputer. Examples are the 6502 or 65C02 microprocessor used in the Apple IIe, the 65C816 microprocessor used in the Apple IIgs, and the 68000 microprocessor used in the Macintosh Plus. See also processor.
microsecond (ms): One millionth of a second.
MIDI: Acronym for Musical Instrument Data Interface; a standard interface for electronically created music.
MIDI synthesizer: A Sound Manager synthesizer that interfaces with external synthesizers via a Musical Instrument Data Interface (MIDI) adapter connected to one of the serial ports.
millisecond (ms): One thousandth of a second.
mini-assembler: A part of the Apple IIgs Monitor program that allows you to create small assembly-language test routines. See also assembler.
mini-window: A type of box that has some but not all features of a regular window. You can reposition a mini-window by dragging its top bar and close it by clicking its close box; however, a mini-window does not have a title and is nonscrolling. In HyperCard, the Message box, Patterns palette, and Tools palette are examples of mini-windows.
minor device number: One of two numbers contained in the inode for a device. The minor device number provides a unit number for the device. Compare major device number.
missing symbol: A character that is drawn in the case of a request to draw a character that's missing from a particular font.
MLI: Abbreviation for Machine Language Interface; the part of ProDOS 8 that processes operating-system calls.
mnemonic: A type of abbreviation consisting of a series of letters and/or numbers that represent a longer or more complicated name or title. A mnemonic is characterized by being relatively easy to remember.
mode: (1) Any of several ways a computer interprets information. (2) A state of a computer or system that determines its behavior. A manner of operating.
modem: Short for modulator/demodulator; a peripheral device that links your computer to other computers and information services using the telephone lines.
modem command: An instruction to a computer system, usually typed from the keyboard, that directs a modem attached to the computer to perform some immediate action.
modem eliminator: A short cable for connecting two Data Terminal Equipment (DTE) devices together without a Data Communication Equipment (DCE) device.
modem port: One of two serial interface ports on the Macintosh computers and on the Apple IIc and IIgs. May be marked by a telephone handset icon.
mode switch: A four-position switch on the back of the LaserWriter that lets you place the LaserWriter in another mode of operation for programming the printer, for emulating a Diablo 630, and so on.
modification date: An attribute of a ProDOS 16 file; it specifies the date on which the content of the file was last changed.
modification time: An attribute of a ProDOS 16 file; it specifies the time at which the content of the file was last changed.
modifier: A program that interprets and processes Sound Manager commands as they pass through a channel.
modifier key: A general term for a key that generates no keyboard events of its own but changes the meaning of other keys or mouse actions; for example, Caps Lock, Command, Control, Apple, Option, and Shift. When you hold down or engage a modifier key while pressing another key, the combination makes that other key behave differently. Sometimes called a control key. Compare character key.
modulate: To modify or alter a signal so as to transmit information. For example, conventional broadcast radio transmits sound by modulating the amplitude (amplitude modulation, or AM) or the frequency (frequency modulation, or FM) of a carrier signal. Compare demodulate.
monitor: See video monitor.
Monitor program: A system program built into the firmware of some computers, used for directly inspecting or changing the contents of main memory and for operating the computer at the machine-language level. The Monitor program activates the disk drive when you turn on the computer.
monochrome monitor: A monitor capable of displaying in only one color; a black-and-white, amber-and-black, or green-and-black monitor.
monospaced font: See fixed-width font. Compare proportional font.
MOS: Acronym for metal oxide semiconductor; a method of making semiconductor integrated circuits using layers of silicon and silicon dioxide. See also CMOS.
most significant bit: The binary digit in a number or data byte that contributes the largest quantity to the value of the number; usually written at the left end of the number. For example, in the binary number 10110 (decimal value 22), the leftmost bit has the decimal value 16 (24). Compare least significant bit.
mount: To install a file system onto the directory hierarchy. Compare unmount.
mounted volume: A volume that has been inserted into a disk drive and has had descriptive information read from it by the File Manager.
mouse: A small device you move around on a flat surface next to your computer. The mouse controls a pointer on the screen whose movements correspond to those of the mouse. You use the pointer to select operations, to move data, and to draw with in graphics programs.
mouse-based application: An application that accepts input from a mouse, as compared with a keyboard-based application.
mouse button: The button on the top of the mouse. In general, pressing the mouse button initiates some action on whatever is under the pointer, and releasing the button confirms the action. Compare button.
mouse-down event: An event generated when the user presses the mouse button.
mouse event: An event generated when the user presses and releases the mouse button. A mouse-down event is generated when the user presses the mouse button. A mouse-up event is generated when the user releases the mouse button.
mouse keys: An Easy Access feature that lets you manipulate the pointer using the 10-key numeric keypad instead of the mouse. See also Easy Access.
mouse scaling: A feature that causes the cursor to move farther during a mouse stroke than it would have otherwise, provided the change in the cursor's position exceeds the mouse-scaling threshold within one tick after the mouse is moved.
mouse-scaling threshold: A number of pixels that, if exceeded by the sum of the horizontal and vertical changes in the cursor position during one tick of mouse movement, causes mouse scaling to occur (if that feature is turned on); normally six pixels.
MouseText: Special characters, like check marks and little apples, used in some mouse-based applications.
mouse-up event: An event generated when the user releases the mouse button.
movable: A memory block attribute, indicating that the Memory Manager is free to move the block. Opposite of fixed. Only position-independent program segments may be in movable memory blocks. A block is made movable or fixed through Memory Manager calls.
move: To change the location of a memory block. The Memory Manager may move blocks to consolidate memory space.
MPW: See Macintosh Programmer's Workshop.
MPW Shell: The application that provides the environment within which the other parts of the Macintosh Programmer's Workshop operate. The shell combines an editor, command interpreter, and built-in commands.
MPW tool: An executable program (type 'MPST') that is integrated with the MPW Shell environment, as opposed to an application, which runs stand-alone.
MS-DOS: The Microsoft Disk Operating System. This is the operating system that governs the IBM PC (under the version PC-DOS) and compatible computers.
MultiFinder: A first-generation multitasking operating system for Macintosh computers that makes it possible to have several applications open at the same time, including background applications that let you perform one task while the computer performs another.
multilaunch application: An application stored on a server that several users can open and use at the same time.
multipart forms: Preprinted forms consisting of an original and one or more attached copies. Such forms can be purchased in pin-feed paper format for use with computer printers.
multiplex: To encode information so that fewer wires are needed to transmit it, and the same cable wires and connector pins can transmit different kinds of information. The NuBus multiplexes information so that 32-bit address and data communication can be performed using a single 96-pin connector and still have adequate pins available for other necessary functions. Specifically, 32 pins are used to transmit a memory address and the same 32 pins (at a different time) to transmit data.
multitasking: A process that allows a computer to perform two or more tasks during a given period of time; it is accomplished by alternating the actions of the computer between tasks. The method by which operating systems, such as A/UX, allow the user to open and run several applications at the same time. For example, multitasking would allow you to receive information from AppleLink, write a memo in MacWrite, and print an Excel spreadsheet-all at the same time.
multi-user: (adj.) Characterizes a mode or ability of an operating system to support several people using the same computer at once.
multi-user document: A document stored on a server that more than one user can open and make changes to at the same time.
multi-user system: An operating system, such as A/UX, that allows many users to access application software simultaneously.
mutual recursion: See indirect recursion.
Glossary N-O
NaN: "Not a Number"; a SANE representation produced when an operation cannot yield a meaningful result.
nanosecond (ns): One billionth of a second.
native mode: The 16-bit operating configuration of the 65C816 microprocessor.
Near Letter Quality: A medium-speed, medium-density print quality on the ImageWriter LQ.
nest: To place folders inside other folders. See also hierarchical file system.
nested loop: A loop contained within the body of another loop and executed repeatedly during each pass through the outer loop. See also loop.
nested subroutine call: A call to a subroutine from within the body of another subroutine.
network: A collection of interconnected, individually controlled computers, together with the hardware and software used to connect them. A network allows users to share data and peripheral devices such as printers and storage media, to exchange electronic mail, and so on.
network administration: Management of the software and hardware that connects computers in a network. This includes such functions as assigning addresses to hosts, maintaining network data files across the network, and setting up internetwork routing. Compare local system administration.
network administrator: The person who is responsible for setting up and maintaining the network.
network connection: A combination of hardware and software that lets you set up a particular implementation of the AppleTalk network system, such as LocalTalk or EtherTalk.
network event: An event generated by the AppleTalk Manager.
Network File System (NFS): A protocol suite developed and licensed by Sun Microsystems that allows different makes of computers running different operating systems to easily share files and disk storage.
New Envelope Stack: An icon in the upper-left part of the AppleFax document window. Dragging the New Envelope Stack to the Envelope View creates an envelope.
newline: Any character, but usually the return character (ASCII code $0D), that indicates the end of a sequence of bytes. A/UX interprets the ASCII line feed character ($0A) as newline, which can be invoked by pressing Return or by pressing Control-J. On the terminal, this character starts a new line by moving the cursor to the first position of the next line. In APW C, newline (\n) is equivalent to carriage return (\r).
newline mode: A mode of reading data in which the end of the data is indicated by a newline character (and not by a specific byte count).
next changeable location: The memory location immediately following the last opened location.
NFS: See Network File System.
nibble: A unit of data equal to half a byte, or four bits. A nibble can hold any value from 0 to 15.
NIL: Pointing to a value of 0. A memory handle is NIL if the address it points to is filled with zeros. Handles to purged memory blocks are NIL.
9-pin plug: A standard plug, having a maximum of nine connector wires (pins), used to connect various devices to a 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.
NLQ: See Near Letter Quality.
node: A device that's attached to an AppleTalk network and communicates by means of the network.
nonbreaking space: The character with ASCII code $CA; drawn as a space the same width as a digit but interpreted as a nonblank character for the purposes of word wrap and selection.
noncoordinated font: A font that either is not assigned to a font class or does not have a correctly formatted name. Compare coordinated font.
non-HFS: See flat file system.
nonrelocatable block: A block whose location in the heap is fixed and can't be moved during heap compaction.
normalized number: A number represented in floating-point notation in which the first bit of the significand is a 1. Compare denormalized number.
NOT: A unary logical operator that produces a true result if its operand is false, and a false result if its operand is true. Compare AND, exclusive OR, OR.
Note Pad: A desk accessory that allows you to enter and edit small amounts of text while working on another document.
note synthesizer: A synthesizer (functionally equivalent to the old square-wave synthesizer) that lets you generate simple melodies and informative sounds such as error warnings.
NTSC: (1) Abbreviation for National Television Standards Committee, which defined the standard format used for transmitting broadcast video signals in the United States. (2) The standard video format defined by the NTSC, also called composite because it combines all the video information, including color, into a single signal.
NuBus: An address bus and data bus incorporated into the system architecture of the Macintosh II. The NuBus architecture lets you add a variety of components to the system, by means of expansion cards installed in NuBus expansion slots inside the Macintosh II. NuBus is a trademark of Texas Instruments.
NuBus expansion slots: The six slots on the main circuit board of the Macintosh II to which you add cards for video monitors and peripheral devices, coprocessors, and network interfaces. See expansion card.
NUL: Refers to ASCII character $00; not to be confused with zero, which is ASCII character $30.
null: (1) An undefined value. Null is different from 0; 0 is a value just like other numbers, whereas null means no value at all (of the expected type). A null string does not contain anything. For example, ' ' is not a null string because it contains a space character; '' represents a null string. (2) Any character or character code that has no meaning to the operating system or program interpreting it. (3) A type of attention cycle.
null event: An event reported when there are no other events to report.
null prefix: A prefix of zero length (and therefore nonexistent).
number class: In SANE, a floating-point number can be characterized as zero, normalized, denormalized, infinity, or NaN.
numeric keypad: A calculator-style keypad, either built-in or peripheral, that you can use to type numbers. The layout of numbers on the keypad makes it easier and faster to use than the regular keyboard. Some application programs designate the keys of a numeric keypad as special function keys. See also keyboard.
object code: See object program.
object file: The form of a routine produced by a language translator such as a compiler or assembler. An object file can be linked to other object files to build a program. Compare source file.
object module format (OMF): The general format used in Apple IIgs object files, library files, and load files.
object program: The translated form of a program produced by a language translator such as a compiler or assembler. Also called object code. Compare source program.
object segment: A segment in an object file. In C, an object segment corresponds to a single function. Compare load segment.
odd parity: The use of an extra bit in data transmission set to 0 or 1 as necessary to make the total number of 1 bits an odd number; used as a means of error checking. Compare even parity, MARK parity, space parity.
off-line: (adj.) Not currently connected to or under the control of the computer. Used to refer to equipment such as printers and disk drives, information storage media such as disks, and the information they contain. Compare on-line.
off-line volume: A mounted volume with all but the volume control block released.
OMF: See object module format.
OMF file: Any file in object module format.
128K Apple II: Any standard Apple II with both main and auxiliary 64K banks of RAM: all models of the Apple IIc and some models of the Apple IIe, including those with the Extended 80-Column Text Card installed. The Apple IIgs is not a 128K Apple II in the strict sense, even though it includes both 64K banks of RAM and is capable of running programs designed for a 128K Apple II.
on-line: (adj.) Currently connected to and under the control of the computer. Used to refer to equipment such as printers and disk drives, information storage media such as disks, and the information they contain. Compare off-line.
on-line help: Assistance you can get from an application program while it's running; for example, HyperCard's disk-based Help system.
on-line volume: A mounted volume with its volume buffer and descriptive information contained in memory.
on/off switch: A switch located on the right side of the ImageWriter LQ, behind the platen knob, that you press to turn the printer on or off.
opcode: See operation code.
open: To make available. You open files or documents in order to work with them. A file may not be read from or written to until it is open. In the desktop interface, opening an icon causes a window with the contents of that icon to come into view. You may then perform further actions in the window when it's active.
Open Apple key: A modifier key on the Apple II-family keyboards, marked with an outlined Apple symbol; on newer keyboards, called the Command key. The key on the Apple IIgs keyboard is marked with both an Apple symbol and a propeller symbol. Compare Solid Apple key.
open architecture: A computer system's ability to use a variety of optional components designed to meet specialized needs, such as video, coprocessing, networking, and so on. An "open" system is one to which a user with no technical background can easily add devices and expansion cards to customize the system.
open collector: A bus driver that drives a line low or doesn't drive it at all.
open driver: A driver that can be read from and written to.
open file: A file with an access path. Open files can be read from and written to.
open permission: Information about a file that indicates whether the file can be read from, written to, or both.
operand: (1) A value to which an operator is applied. Compare argument. See also operator. (2) In assembly language, the part of an instruction that follows the operation code. The operand is used as a value or an address, or to calculate a value or an address. (3) In object module format, an operation code that is followed by a single value that constitutes part of an expression. The value following the operand opcode is acted on by an operator.
operating environment: The overall hardware and software setting within which a program runs. Also called execution environment.
operating system: (1) A program that organizes the actions of the parts of the computer and its peripheral devices. (2) Low-level software that controls a computer by performing such basic tasks such as input/output, memory management, and interrupt handling. See also disk operating system.
operating-system call: A request to execute a named operating-system function; also, the name of the function itself. OPEN, GET_FILE_INFO, and QUIT are ProDOS 16 operating-system calls.
Operating System Event Manager: The part of the Macintosh Operating System that reports hardware-related events such as mouse-button presses and keystrokes.
Operating System Utilities: Operating-system routines that perform miscellaneous tasks such as getting the date and time, finding out the user's preferred speaker volume and other preferences, and doing simple string comparison.
operation code: The part of a machine-language instruction that specifies the operation to be performed. Often called opcode.
operator: (1) A symbol or sequence of characters, such as + or AND, specifying an operation to be performed on one or more values (the operands) to produce a result. (2) In object module format, an operation code that specifies an arithmetic or logical operation in an expression to be performed on one or two variables that precede it. The variables acted on by an operator are identified by operand opcodes that precede them. See also arithmetic operator, binary operator, Boolean operator, relational operator, unary operator.
optical storage: An information medium in which stored information is readable by a light detector. Information is recorded on CD-ROM discs as a pattern of pits and land (unpitted areas). The photodetector in the optical read head can tell the difference between pits and land by sensing the difference in the amount of light that is reflected.
option: (1) Something chosen or available as a choice; for instance, one of several check box or radio button options. (2) An argument whose provision is optional.
optional character set: An alternate character set that includes special symbols, and foreign characters and accents. You view it with the Key Caps desk accessory.
option card: A card that contains electronic circuits that implement specialized functions. Some examples are coprocessors and accelerators.
Option key: A modifier key that gives a different meaning or action to another key you press or to mouse actions you perform. For example, you can use it to type foreign characters or special symbols contained in the optional character set. On the Apple IIgs and some models of the Apple IIe, the Option key replaces the Solid Apple key.
OR: A logical operator that produces a true result if either or both of its operands are true, and a false result if both of its operands are false. Compare AND, exclusive OR, NOT.
output: (n.) Information transferred from a computer to some external destination, such as the display screen, a disk drive, a printer, or a modem. Compare input. (v.) To transfer information in such a way.
output device: A device that receives information from the microprocessor. The monitor is the Macintosh's primary output device. Compare input device.
output driver: A device driver that receives data via a serial port and transfers it to an application.
output routine: A machine-language routine that performs the sending of characters. The standard output routine sends characters to the screen. A different output routine might, for example, send them to a printer. Compare input routine.
overflow: The condition that exists when an attempt is made to put more data into a given memory area than it can hold; for example, a computational result that exceeds the allowed range.
override: To modify or cancel an instruction by issuing another one. For example, you might override a DIP switch setting on a printer with an escape sequence.
overrun: The condition that occurs when the processor does not retrieve a received character from the receive data register of the Asynchronous Communications Interface Adapter (ACIA) before the subsequent character arrives. The ACIA automatically sets bit 2 (OVR) of its status register; subsequent characters are lost. The receive data register contains the last valid data word received.
overrun error: See hardware overrun error, software overrun error.
owner: The registered AppleShare file server user who created a folder or was assigned ownership of a folder or volume. The owner is named in the Access Privileges window.
Owner: The AppleShare user category that the owners of folders or volumes use to assign access privileges to themselves.
Glossary Pl-Pz
plain envelope: An envelope that has been addressed with an AppleFax address or an AppleFax-distribution list. Plain envelopes can hold fax files and Macintosh files; plain envelopes must be sent to AppleFax Stations.
plain text document: A document that you can open, read, and print without having to use a full-feature word processing application. To read plain text documents, use the TeachText application on the System Tools disk. See
also Read Me document.
plane: The front-to-back position of a window on the desktop.
platen: The rubber roller in a printer that provides support for the paper while the printhead prints on it.
platen knob: The knob at the right side of the ImageWriter LQ printer. Turning the knob clockwise advances paper into and out of the printer.
plotter: A peripheral device that allows you to draw charts and graphs by means of pens whose movements are controlled by the computer.
plotting vector: A code representing a single step in drawing a shape on the high-resolution graphics screen. The plotting vector specifies whether to plot a point at the current screen position, and in what direction to move (up, down, left, or right) before processing the next vector. See also shape definition, shape table.
PMMU: The Motorola 68851 Paged Memory Management Unit, which allows an operating system to quickly reconfigure the arrangement of memory without physically moving data, so that different tasks can be "swapped" within the same space. The PMMU chip is needed with multitasking operating systems such as A/UX.
point: (1) A unit of measurement for type. Twelve points equal 1 pica, and 6 picas equal 1 inch; thus, 1 point equals approximately 1/72 inch. (2) The intersection of a horizontal grid line and a vertical grid line on the coordinate plane, defined by a horizontal and a vertical coordinate.
pointer: (1) A small shape on the screen that follows the movement of the mouse or shows where your next action will take place. The pointer can be an arrow, an I-beam, a crossbar, or a wristwatch. (2) An item of information consisting of the memory address of some other item. For example, Applesoft BASIC maintains internal pointers to the most recently stored variable, the most recently typed program line, and the most recently read data item, among other things. The 6502 uses one of its internal registers as a pointer to the top of the stack.
point of call: The point in a program from which a subroutine or function is called.
POKE: An Applesoft BASIC command that stores information directly into a location in the computer's memory.
polling: An option that enables a fax station at one location to automatically retrieve files and documents from a fax station at another location.
polygon: A sequence of connected lines, defined by QuickDraw line-drawing commands.
pop: To remove the top entry from a stack, moving the stack pointer to the entry below it. Synonymous with pull. Compare push.
port: (n.) (1) A socket on the back panel of a computer where you plug in a cable for connection to a network or a peripheral device. (2) A connection between the central processor unit and main memory or a device (such as a terminal) for transferring data. (v.) To move software from one hardware architecture to another.
positional parameter: A variable set on the command line of a shell script and operating as an argument to the script. This variable is called by number, usually 0 through 9, within the shell script. The number refers to the position of the parameter on the command line.
position independent: Describes code that is written specifically so that its execution is unaffected by its position in memory. It can be moved without needing to be relocated.
post: To place an event in the event queue for later processing.
postfix notation: In programming languages, a type of notation in which the variable is followed by the operator (either ++ to increment the variable or - - to decrement the variable). Postfix notation changes the value of the variable after the value has been used. Compare prefix notation.
postfix operator: See postfix notation.
postprocessor: A utility that accepts as its input the output from another utility. For example, psdit is a postprocessor that accepts troff output and transforms it into a form suitable for printing on Apple LaserWriters and other PostScript-supported printers.
power: In the CloseView utility, the level of magnification. For example, with the power set at 4x, screen images appear four times as large when magnified.
power cord: A cord used solely to connect a device to its source of electricity. Some devices, such as most disk drives, do not require a separate power cord.
power key: In HyperCard, one of a number of keys on the Macintosh keyboard you can press to initiate a menu action when a Paint tool is active. Power keys are enabled when you choose Power Keys from the Options menu or check Power Keys on the User Preferences card in the Home stack.
power light: A light that glows when a computer or peripheral device is turned on.
Power On key: A key on the keyboard that starts the MacintoshII.
power socket: The socket at the back of a device such as a hard disk, computer, or printer into which you plug the power cord.
power strip: A device that plugs into one three-hole, grounded outlet but can accommodate four or six three-pronged plugs. A power strip is a must if you have more than two devices that need to be plugged into a three-hole, grounded outlet.
power supply: A circuit that draws electrical power from a power outlet and converts it to the kind of power the computer can use.
power supply case: The metal case inside most Apple II and Macintosh computers that houses the power supply. The Apple IIc uses an external power supply case.
power switch: A switch on the computer or printer that you turn on when you want to use it.
PR#: An Applesoft BASIC command that sends output to a slot or a machine-language program; it specifies an output routine in the ROM on a peripheral card or in a machine-language routine in RAM by changing the address of the standard output routine used by the computer. For example, in the Apple II family of computers PR#1 sends output to the device located in slot 1, and PR#0 returns output to the video display.
precedence: The order in which operators are applied in evaluating an expression. Precedence varies from language to language but usually resembles the precedence rules of algebra.
prefix: (1) The frst part of a pathname-the name of the disk and, if you like, the name of a subdirectory. Applications that ask you to type a pathname usually let you set a prefx so you don't have to type the complete pathname every time you want to work with a document on a particular disk or in a particular subdirectory. Once the prefx is set, all you do is type the rest of the pathname. (2) A designation for a place that an application can store files. Many applications require the prefix to be the same as the pathname. Some applications allow you to set the prefix from within the application. See also full pathname, partial pathname.
prefix notation: In programming languages, a type of notation in which the variable is preceded by the operator (either ++ to increment the variable or - - to decrement the variable). Prefix notation changes the value of the variable before using its value. Compare postfix notation.
prefix number: A code used to represent a particular prefix. Under ProDOS 16, there are nine prefix symbols, consisting of the numerals 0 through 7 and the asterisk followed by a slash: 0/, 1/, ... 7/, and */.
premastering: The process of writing information onto a 9-track tape, which is then used to create a master compact disc.
preprocessor: (1) A utility used to transform data that is then written to another utility. For example, tbl is a preprocessor that formats tables from properly coded text files; the output of this processor is usually piped to a more general text formatter like troff. (2) A function of certain compilers that provides file inclusion, comment deletion, and macro substitution.
preprocessor symbol: In C, one of a set of constants defined to be 1, equivalent to writing #define symbol 1 at the beginning of the source file.
press: (1) To position the pointer on something on the screen and then hold down the mouse button without moving the mouse. (2) To push a key down and then release it; you hold a key down only if you want to repeat a character or if you are using a modifier key with another key.
primary group: The AppleShare group with whom you'll most often be sharing the documents you store on a server. Primary groups are specified by the administrator.
print buffer: Memory in the printer that stores text until it can be printed, as when the data transmission rate exceeds the printing speed. The last line remaining in the print buffer is not printed until a print command is received or a full line of text has been received. The print buffer is sometimes called the input buffer. See also current line, print command.
print command: A command that causes printing, such as a carriage return. Data in the print buffer is not printed until the buffer contains a full line of text or a print command is received.
print density dial: A dial on the back of the LaserWriter printer that allows you to change how dark or light the image will be on the printed page.
printed-circuit board: A hardware component of a computer or other electronic device, consisting of a flat, rectangular piece of rigid material, commonly fiber glass, to which integrated circuits and other electronic components are connected.
printer: A device that produces a paper copy of the text or graphics you create using your computer. See also daisy wheel printer, dot matrix printer, laser printer.
printer command: One or more characters sent to the printer to control some function, such as turning boldface printing on or off, or to cause some action, such as a line feed.
printer driver: A program that controls the exchange of information between a printer and the computer. You must have a separate printer driver for each type of printer that you want to use. See also print manager.
printer font: A bitmapped font intended for use by the printer rather than for use on the screen. Compare screen font. See also internal font.
printer port: A socket on the back panel of the computer marked by a printer icon. In addition to being a connection for a printer, a printer port also serves as the usual attachment point for an LocalTalk connector on Macintosh computers.
printer resource file: A file containing all the resources needed to run the Apple IIgs Printing Manager with a particular printer.
printer software: See resource.
print head: In the Apple ImageWriter LQ, the part that moves horizontally along the platen and performs the actual printing.
printing GrafPort: A special GrafPort customized for printing instead of drawing on the screen.
Printing Manager: The routines and data types that enable applications to communicate with the Apple IIgs Printer Driver to print on any variety of printer via the same interface.
printing resource: A system file that lets you print on a corresponding printer attached to the computer. Sometimes called a printer driver. See also resource.
print line: The bottom line on the paper guide that indicates where the printer begins printing on the paper. The print line is 1/6 inch below the top-of-form line and the top edge of the paper.
print log: A chronological list of documents formerly in the print queue.
print manager: A firmware or software program that provides routines for controlling printing. Your program calls the print manager routines, and the print manager calls the printer driver for the appropriate printer; this procedure makes it unnecessary for your program to include a separate printing routine for each type of printer you want to support.
PrintMonitor: An application that monitors background printing and provides options intended to give you additional control over what happens to documents you are printing. See also background processing.
printout: A paper copy of text and graphics; that which is produced by a printer.
Print Quality light: A set of indicators on the ImageWriter LQ control panel that show whether Draft Quality, Near Letter Quality, or Letter Quality printing is selected for a document produced on an Apple II. Macintosh print quality is determined by software settings.
print queue: A collection of spooled documents, awaiting printing, stored on the print server disk and printed in order.
print record: A record containing all the information needed by the Printing Manager to perform a particular printing job.
print server: A combination of software and hardware that stores documents sent to it over the AppleTalk network and manages the printing of those documents on a LaserWriter.
print spooler: A utility that writes a representation of a document's printed image to disk or to memory, schedules it to print in a queue of other jobs, and then prints it.
print wheel: See daisy wheel.
procedure: In the Pascal and Logo programming languages, a set of instructions that work as a unit; approximately equivalent to the term subroutine in BASIC.
process: An instance of a program in execution. Usually one copy of a program is stored on a UNIX system like A/UX, but multiple instances of the program-each having its own address space-can be executed simultaneously as separate processes.
process ID (PID): A unique number assigned to each process being executed on the system. The PID is listed with its associated command when you enter the ps command. The PID is sometimes called a process number.
processor: The hardware component of a computer that performs the actual computation by directly executing instructions represented in machine language and stored in main memory. See also microprocessor.
processor priority: Bits 8 to 10 of the 68000 status register, indicating which interrupts will be processed and which will be ignored.
process scheduling: Multitasking process management performed by the kernel. The central processor unit (CPU) can only execute processes one at a time. By equitably scheduling their execution, the kernel lets multiple processes share the CPU efficiently.
process status: The names, states, and process numbers of commands submitted for execution; the ps command displays this information.
ProDOS: A family of disk operating systems developed for the Apple II family of computers. ProDOS stands for Professional Disk Operating System and includes both ProDOS 8 and ProDOS 16. Compare DOS 3.3, DOS 3.2.
ProDOS 8: A disk operating system developed for standard Apple II computers. It runs on 6502-series microprocessors and on the Apple IIgs when the 65C816 processor is in 6502 emulation mode.
ProDOS 16: A disk operating system developed for 65C816 native mode operation on the Apple IIgs. It is functionally similar to ProDOS 8 but more powerful.
program: (n.) (1) A set of instructions describing actions for a computer to perform to accomplish some task, conforming to the rules and conventions of a particular programming language. (2) A file containing coded instructions to the computer. A compiled program is a file first created in source code and then transformed by the compiler into object code. A shell program is a text file that does not need to be compiled, because it is interpreted by the shell. (v.) To write a program.
program disk: A disk that contains an operating system and a self-starting application program.
program line: The basic unit of an Applesoft BASIC program, consisting of one or more statements separated by colons (:).
programmable read-only memory (PROM): A type of ROM device that is programmed after fabrication, unlike ordinary ROM devices, which are programmed during fabrication.
programmer: The author of a program; someone who writes programs.
programming language: A set of symbols and associated rules or conventions for writing programs. For example, BASIC, Logo, and Pascal are programming languages.
program segment: One or more code segments and, optionally, data segments assembled together to perform a function.
PROM: See programmable read-only memory.
prompt: (1) A message on the screen that tells you of some need for response or action. A prompt is usually in the form of a symbol, a message, a dialog box, or a menu of choices. (2) Short for prompt character.
prompt character: A text character displayed on the screen, usually just to the left of a cursor, where your next action is expected. The prompt character often identifies the program or component of the system that's prompting you. For example, Applesoft BASIC uses a square bracket prompt character (]); Integer BASIC, an angle bracket (>); and the system Monitor program, an asterisk (*). The Bourne and Korn shells are set by default to display the dollar sign ($) as their prompts; the C shell is set by default to display the percent sign (%) as its prompt.
prompt line: A specific area on the display reserved for a prompt.
proportional font: (1) Any font in which different characters have different widths; thus, the space taken up by words having the same number of letters may vary. For example, in the typeface used here the letter M is wider than the letter I, so that MMMMM produces a wider string than IIIII. (2) A font whose characters all have character widths that are proportional to their image width. Compare fixed-width font.
protocol: Short for communications protocol; a formal set of rules for sending and receiving data on a communication line. For example, binary synchronous communications (BSC) is a protocol.
Protocol Converter: A set of ROM-based assembly-language routines used to support external input/output devices, such as the Apple Memory Expansion Card and the Apple 3.5 Drive.
protocol handler: A software process in a node that recognizes different kinds of frames by their ALAP type and services them.
pseudorandom numbers: A sequence of numbers, determined by some defined arithmetic process, that is satisfactorily close to a true random sequence for a given purpose. Microcomputers can generate pseudorandom numbers and thus can simulate games of chance, such as dice-based games and card games.
public-domain software: Software that is free for the taking. You can get it at user group meetings or through computer bulletin boards.
pull: To remove the top entry from a stack, moving the stack pointer to the entry below it. Synonymous with pop. Compare push.
pull-down menu: A menu that is hidden until you move the pointer to its title and press the mouse button.
pull tractor: In the ImageWriter LQ printer, a tractor that pulls pin-feed paper into the printer from either the rear or the bottom of the printer, and feeds it out the rear.
purge: To temporarily deallocate a memory block. The Memory Manager purges a block by setting its master pointer to NIL (0). All handles to the pointer are still valid, so the block can be reconstructed quickly. Compare dispose.
purgeable: A memory block attribute, indicating that the Memory Manager may purge the block if it needs additional memory space. Purgeable blocks have different purge levels, or priorities for purging; these levels are set by Memory Manager calls.
purgeable block: A relocatable block that can be purged from the heap.
purge level: An attribute of a memory block that sets its priority for purging. A purge level of 0 means that the block cannot be purged.
push: To add an entry to the top of a stack, moving the stack pointer to point to it. Compare pull.
push tractor: In the ImageWriter LQ printer, a tractor that pushes pin-feed paper under the platen when the paper is fed into the rear of the printer, and feeds it out the top.
