Glossary of Terms

ADC
Apple Display Connector. This connector carries a DVI video signal, power for the display and USB.

Administrator
When you first install or setup Mac OS X, you are asked to create a user. This first user is an administrator. An administrator has privileges to create other users, including other administrators, install software, and change various computer settings.

AirPort-ready
A Macintosh computer with AirPort antennae installed and a slot that accepts an AirPort card.

AGP
Accelerated Graphics Port. AGP is a bus style that allows the graphics card to have a dedicated bus directly to the system memory. Older PCI video cards that shared data bandwidth with all installed PCI cards as well as internal I/O controllers such as IDE, SCSI, and the like. AGP allows the graphics card to be taken off that PCI bus and put onto it's own dedicated 133 MHz data bus. AGP also introduced a new slot type allowing AGP cards to transfer data faster.

AltiVec or Velocity Engine
The Velocity Engine can process data in 128-bit chunks, instead of the smaller 32-bit or 64-bit chunks used in traditional processors (it's the 128-bit vector processing technology used in scientific supercomputers--except that Apple has added 162 new instructions to speed up computations). In addition, it can perform four (in some cases eight) 32-bit floating-point calculations in a single cycle--2-4 times faster than traditional processors.

AppleTalk
A comprehensive network system developed by Apple that runs on a variety of cable systems and protocols. It facilitates communication between network devices, such as computers, file servers, and printers, which may be a mixture of Apple and non-Apple products. Several elements make up an AppleTalk network system: AppleTalk software and AppleTalk hardware; the latter includes computing components and connectivity components. AppleTalk's design allows the inclusion of a variety of data-link and cabling methods in a network system. Data-link and cabling methods widely used include LocalTalk, EtherTalk (using standard Ethernet media), and TokenTalk (using token ring media).

ASCII
(Pronounced "as-key.") American Standard Code for Information Interchange -- a commonly used data format for exchanging information between computers or programs.

Background
An aspect of multitasking capability. A program can run and perform tasks in the background while another program is being used in the foreground.

Backup
A copy of a file or disk made for archiving purposes.

baud
Baud is an older measurement for data transmission speed. One baud is one change of electronic state per second. A more accurate (and therefore more widely used) term is bps (bits per second) -- see above.

Bit
("Binary digit"). The smallest piece of information that is used by the computer. In computer language, either a one (1) or a zero (0) -- to create a 1 or a 0, the tiny microcircuit in question is literally "off" or "on."

Bitmap
A pixel-by-pixel representation of an object.

Boot
To start up a computer.

bps
Bits per second. A measurement of the speed at which data travels from one place to another; sometimes expressed as Kbps (thousands of bits per second) or Mbps (millions of bits per second).

Bus
An electronic pathway for data transmitted between devices in a computer.

Byte
A piece of computer data made up of eight bits.

Cache memory
Cache RAM is fast random-access memory that is used to store data for CPU operations. Level 1 cache RAM is part of the CPU itself; level 2 (L2) cache RAM is on separate chips.

Card
A printed circuit board that, when inserted into a logic board slot, adds some capacity to a computer.

CD-ROM
Compact Disc - Read Only Memory, often shortened to CD. One of the most popular ways to distribute programs today. These discs can hold over 600 megabytes of data and are easily portable.

CD-RW
Short for CD-rewritable disk, a type of CD disk that enables you to write onto it in multiple sessions. Macintosh computers have slot-loading or tray-loading CD-RW drives.

Client
A program that requests services from other programs or computers that are functioning as "servers" or "hosts."

Clock rate
The processing speed of a computer measured in millions of cycles per second (for example, 800 MHz).

Combo
An optical drive that writes CD-R discs; writes CD-RW discs; reads DVD-ROM discs; and reads CD-ROM discs.

Console
The Console application lets you see technical messages from the Mac OS X system software and Mac OS X applications. If you are programming or troubleshooting a problem, these messages may be useful.

CPU
The central processing unit (microprocessor). In current Power Mac, iMac, PowerBook, and iBook computers, the CPU is a PowerPC G3 or G4 chip. Earlier models contained PowerPC (601, 603, 604, 604e) and Motorola 680x0 chips.

Cursor
The pointer, usually arrow or cross shaped, which is controlled by the mouse, trackpad, trackball, stylus, or joystick.

Daisy-chaining
Stringing external devices together in a series. (SCSI, USB, and FireWire technologies all allow such linking of devices in most cases).

Data
Plural of "datum." Information processed by a computer.

Default
The setting that a program automatically selects. You can select the default action by pressing Return or Enter. The default action in a Mac OS 9 dialog is usually represented by the button with a double outline.

Defragmentation
Arranging fragments of data into contiguous blocks in RAM or storage memory (also called "optimizing").

Digitize
Converting linear (analog) data into digital data which can be used by a computer.

Disk
A platter made of magnetic or optically etched material on which data can be written.

Download
Transferring data from one computer to another. (Downloading is receiving; uploading is sending).

DPI
Dots per inch; the number of dots that can be placed horizontally and vertically. This is also known as printer resolution.

Driver
A file that tells a computer how to communicate with a peripheral such as a CD-ROM drive or printer.

DVD-ROM
Short for digital versatile disc or digital video disc, a type of CD-ROM that holds a minimum of 4.7GB (gigabytes), enough for a full-length movie. Often shortened to DVD.

DVD-RAM
Digital Versatile Disc - Random Access Memory. A high storage capacity, writable version of DVD technology (good for backing up hard disk data).

DVI
Digital Visual Interface. DVI is a technology developed by a consortium of companies that enables a system to store and display moving video images. A DVI connector is more advanced than a standard VGA connector. With DVI all content transferred over the interface remains in the loss-less digital domain from start to finish for high-quality digital images.

Encoding
An algorithm for converting files into a series of 7-bit ASCII characters that can be transmitted over the Internet.

Ethernet
A protocol for communication and file transfer across a network.

FireWire
FireWire is Apple's cross-platform implementation of a high-speed serial data bus (defined by IEEE Standard 1394-1995) that is able to transfer large amounts of data between computers and peripheral devices. FireWire features simplified cabling and hot swapping, and provides a single plug-and-socket connection to which up to 63 devices can be attached with data transfer speeds up to 400 Mbps (megabits per second). Firewire is designed to support much higher data rates than USB; both standards are expected to exist together, serving different device types.Firmware Software that has been written onto read-only memory (ROM).

Font
A typeface that contains the characters of an alphabet, numbers, and some other letterforms (such as punctuation marks).

Fragmentation
The breaking up of a file into many separate locations in memory or on a disk. It takes longer to retrieve files that are highly fragmented.

Footprint
The surface area of a desk or table which is occupied by a piece of equipment.

ftp
File Transfer Protocol. A method of transferring files from one computer to another via the Internet.

G3 and G4
The RISC-based PowerPC processing chips designed by Apple, IBM, and Motorola.

Gigabyte
One thousand (actually 1024) megabytes. A term used to describe RAM or hard disk storage space. (Abbreviation: GB, Gig).

Gigahertz
Abbreviated as GHz. One GHz represents one billion cycles per second.

Handshaking
The system by which communications between devices are started and stopped. The sender issues a 'request' or 'ready' signal and the receiver sends back an 'acknowledgment' or 'proceed' signal.

Hard disk (or hard disk drive, or hard drive)
Large-capacity, permanent storage for the computer (used for storing applications and files), made of multiple disks housed in a rigid case.

HTML
HyperText Markup Language. A set of simple tags that tells a computer how to display the text, graphics, and other objects that comprise a Web page.

Initializing
Formatting a disk for use in the computer. Initializing creates a new directory and arranges the tracks for the recording of data. Initializing erases all data on the disk.

IP (Internet Protocol) address
A computer's unique Internet address (such as 128.223.32.35) that identifies it on a TCP/IP-protocol network. Many computers also have a "domain name" assigned to them, which represents IP addresses as words that are easier to remember (such as, apple.com).

Kernel panic
A kernel panic is a type of error that occurs when the core (kernel) of an operating system receives an instruction in an unexpected format or that it fails to handle properly. When this happens in either Mac OS X or Mac OS X Server, white text on a black background is drawn on top of the last video image on the monitor before the error occurred. A kernel panic can also be caused by damaged or incompatible software or, more rarely, damaged or incompatible hardware.

Kilobit
One thousand bits. (Abbreviation: Kb)

Kilobyte
One thousand (actually 1024) bytes. (Abbreviation: K, KB)

Launch
Start an application.

Log in
When you first set up Mac OS X, you do not need to log in to your computer. If you want to log in each time you start up your computer, open System Preferences, click Login, click Login Window, and deselect "Automatically log in." You can also turn off automatic login when you create a new user for the computer.

Logic board
Also called the motherboard. The main circuit board of a microcomputer.

Math coprocessor
Also known as the floating-point arithmetic unit (FPU). Adds additional arithmetic and trigonometric processing to that provided by the CPU. (In PowerPC-based computers the FPU is part of the CPU.)

Megabit
One thousand kilobits. (Abbreviation: Mb)

Megabyte
One million bytes. A term used to describe RAM or hard disk storage space. (Abbreviation: MB, Meg)

Megahertz
Abbreviated as MHz. One MHz represents one million cycles per second. The speed of microprocessors ("clock speed") and system buses is measured in megahertz.

Memory
The temporary holding area where data is stored while it is being used or changed; the amount of RAM a computer has installed.

Modem
Acronym for modulator-demodulator. A modem is a device that enables a computer to transmit data over telephone lines.

Monitor or Display
Another term for display screen. You may encounter CRT (cathode-ray tube) displays, or flat panel displays.

Mouse
A device that controls the movement of the cursor or pointer on a display screen.

MPEG
Short for Moving Picture Experts Group, and pronounced m-peg, a working group of ISO. The term also refers to the family of digital video compression standards and file formats developed by the group.

Multitasking
The concurrent execution of multiple programs. Mac OS X uses preemptive multitasking. Mac OS 8 and 9 use cooperative multitasking.

Nanosecond
One billionth of a second.

Network
Two or more computing devices connected together by wiring, cable, digital circuit, or other means. The Internet is a network that comprises thousands of computer networks.

Open Firmware
Open Firmware is a cross-platform firmware standard for controlling hardware and is used by all PCI-based Mac OS computers. You can start up in Open Firmware when troubleshooting.

OpenGL
OpenGL enables the computer to display accelerated three-dimensional graphics using applications designed to take advantage of OpenGL, including graphics cards with RAGE II, RAGE Pro, RAGE 128 and Radeon based video 2D and 3D graphics APIs (application program interfaces).

Operating system (or OS)
Software that coordinates the internal activities of the computer and its peripheral devices. An operating system performs basic tasks such as moving data to and from devices and managing information in memory.

Parallel port
A port that allows data to be transmitted in a series. Printers and webcams, for example, use parallel ports.

Partition
A subdivision of a hard disk's area that is defined and used as a separate volume.

PCI
Peripheral Component Interchange. A bus architecture.

PCMCIA or PC card
Short for Personal Computer Memory Card International Association. An organization that has developed a standard for small, credit card-sized devices, called PC Cards suitable for many types of devices, including data storage and modem devices.

PDF
Short for Portable Document Format, a file format developed by Adobe Systems.

Peripheral
A component (such as a printer) added to a computer.

Pixel
The smallest component of an on-screen image (the smallest area that can be addressed in both the horizontal and vertical direction).

Port
A connection socket, or jack on a computer.

PostScript
A language that is used to describe graphic objects on a printed page. A PostScript interpreter is software that executes a PostScript language program and turns the description of an object into bits in a frame buffer. (PostScript!" is a trademark of Adobe Systems Incorporated.)

PowerPC
Any one of the RISC-based processing chips (601, 603, 604, 604e, G3, or G4) designed by Apple, IBM, and Motorola.

PRAM
Parameter RAM. PRAM stores date and time settings and other system preference data.

Print spooler
A program that stores documents to be printed, thereby freeing memory and allowing other functions to be performed while printing goes on in the background.

Protocol
A precise definition of how computers interact with one another on a network.

QuickTime
A technology from Apple for handling video, sound, animation, graphics, text, music, and 360-degree virtual reality (VR) scenes. QuickTime lets you experience more than 200 kinds of digital media with your Mac or PC including images, music, MIDI, and MP3. As of August, 2001, the current version is QuickTime 5 (available as a free download).

RAM
Random-access memory, sometimes referred to as main memory. The Macintosh RAM provides memory for system software and applications. In sleep mode, the contents of RAM are maintained. Shutting down the computer erases RAM contents. There are various types of RAM, including DRAM (dynamic random-access memory) and SDRAM (synchronous random-access memory).

Reset switch
A switch that restarts the computer in the event of a crash or freeze.

RGB
The additive colors Red, Green, and Blue. These colors can be combined to obtain white or any color of the spectrum, and are usually used in color displays (which are referred to as RGB displays).

RISC
Reduced Instruction Set Computing. A smaller set of commands that optimizes efficiency and speed in microprocessing. Because RISC chips use a smaller instruction set, they operate much faster than the older CISC (Complex Instruction Set Computing) chips used in Intel-based machines and in older Macintosh systems. (See also megahertz for more information on microprocessing speed.)

ROM
Read-only memory. The Macintosh ROM contains system command sets.

SCSI
Small Computer Systems Interface. A specification of mechanical and electrical standards for connecting certain peripheral devices (such as CD-ROM drives, external storage drives, and scanners) to a computer. SCSI has been replaced by USB and FireWire on newer Macintosh models.

Server or Host
A central computer dedicated to sending, storing, and receiving data from other computers on a network. The server or host provides services to other "client" computers on a network. On the Internet, a single computer often provides multiple host functions, such as processing e-mail, serving Web pages, and running applications.

SuperDrive
A combination CD-RW/DVD-R drive that can read and write CDs as well as DVDs that can be played in consumer DVD players.

TCP/IP
Transmission Control Protocol/Internet Protocol. These are two of the main "protocols" of the Internet. To connect a computer to the Internet, it must have some kind of TCP/IP communication software installed on it.

Terabyte
2 to the 40th power (1,099,511,627,776) bytes. This is approximately 1 trillion bytes or one thousand gigabytes.

Terminal
The Terminal applications lets you use a command-line interface and BSD (a version of UNIX developed at UC Berkeley) utility programs.

URL
Uniform Resource Locator. A term for the address of an Internet site or other resource.

VGA and SVGA
Abbreviations of video graphics array and Super VGA. VGA is a graphics display system developed by IBM.

Video RAM
Video random-access memory. Supplies display memory additional to that provided in main memory. With more VRAM, more colors and higher screen resolutions are available.

Virtual memory
Virtual memory is hard disk space that the computer uses as if it were RAM. Disk space used for virtual memory is not available for storing files. Data stored in virtual memory is lost on shut down (as with physical RAM).

World Wide Web
A system of linked servers that distribute pages of hypertext (HTML), graphics, and multimedia information to users all over the world. Frequently shortened to the Web.