.Mac - A suite of Mac-only Internet services. .Mac includes email, online storage (iDisk), web home pages, Internet postcards (iCards), calendar sharing with iCal, information synchronizing with iSync, and backup and virus protection software.

M3U File - An audio metafile that is created using a text editor and saved to a web server. The file directs a user's web browser to an MP3 playlist residing on the same web server and opens the user's MP3 player.

MAC (Media Access Control) address - A computer's unique hardware number for networking.

Mac OS X Architecture - Refers to how Mac OS X is designed, and how different application environments are connected together.

Mac OS X Server - An industrial-strength server platform that supports Mac, Windows, UNIX, and Linux clients out of the box and provides a suite of scalable workgroup and network services plus advanced remote management tools.

Mac OS X - The latest version of the Apple operating system, which combines the reliability of UNIX with the ease of use of Macintosh.

Mac OS - Macintosh Operating System.

Machine Language - The binary language of 1's and 0's that is the only language the computer understands. All other programming languages, like BASIC, have to be translated into this binary code before the computer can understand them.

Mach - The lowest level of the Mac OS X kernel. Mach provides such basic services and abstractions as threads, tasks, ports, interprocess communication IPC scheduling, physical and virtual address space management, virtual memory, and timers.

Macro - A command defined by you user-defined that tells the application to carry out a series of commands when you type the macro.

Mail Host - The computer that provides your mail service.

Mail Server - A computer with one or more hard disks for storing electronic messages and files.

Mail-Merge Application - An application that takes names and addresses from a data base and puts them into form letters.

Main Circuit Board - A large circuit board that holds RAM, ROM, the microprocessor, custom integrated circuits chips, and other components that make the computer a computer. Also called a circuit board.

Main Menu - The first menu you see in keyboard-based applications. It presents the application's top level of options.

Make/Break Ratio - The make/break ratio is used in pulse dialing. It specifies the ratio of off-hook make time to on-hook break time for each pulse. You use the &Pn command to set the make/break ratio. Phone systems in different countries require different make/break ratios.

mA - Milliamperes.

Managed Client - A user, group, or computer whose access privileges and/or preferences are under administrative control.

Managed Preferences - System or application preferences that are under administrative control. Server Manager allows administrators to control settings for certain system preferences for Mac OS X managed clients. Macintosh Manager allows administrators to control both system preferences and application preferences for Mac OS 9 and Mac OS 8 managed clients.

Manual Unicast - A method for transmitting a live stream to a single QuickTime Player client or to a computer running QTSS or DSS. An SDP file is usually created by the broadcaster application and then must be manually sent to the viewer or streaming server.

Mass Storage Device - A device, like a hard disk, that can store the equivalent of dozens of disks.

Match Back - To match the edits of a video program sourced from film back to the original camera negative. All the edits to the video are listed in a cut list, which the negative cutter uses to cut the workprint and original camera negative.

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.

MB/sec. - Megabytes per second.

Mbit - Megabit.

MB - Megabytes.

MBONE Multicast Backbone - A virtual network that supports IP multicasting. An MBONE network uses the same physical media as the Internet, but is designed to repackage multicast data packets so they appear to be unicast data packets.

Mbps - Megabits per second.

Media - Content such as DV clips, sound effects, music tracks, or still images.

Medium - The means by which devices on a network are linked together to communicate and share information. Types of media include physical cables as well as infrared light and radio frequency signals.

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, called the clock speed, is measured in megahertz. In addition to microprocessors, the speeds of buses and interfaces are also measured in MHz.

Memory Expansion Card - An interface card that you can connect to the memory expansion slot in the Apple IIgs to increase the memory by 1 to 8 megabytes.

Memory Paging - A technique used by virtual memory operating systems to help ensure that the data you need is available as quickly as possible. The operating system copies a certain number of pages from your storage device to main memory. When a program needs a page that is not in main memory, the operating system copies the required page into memory and copies another page back to the disk.

Memory Protection - A system of memory management in which programs are prevented from being able to modify or corrupt the memory partition of another program. Mac OS 8 and Mac OS 9 do not have memory protection; Mac OS X does.

Memory - Integrated circuits chips that store instructions for the microprocessor. There are two kinds of memory-temporary memory called random-access memory RAM and permanent memory called read-only memory ROM. The contents of RAM disappear when you turn off the power; the contents of ROM do not. The temporary holding area where data is stored while it is being used or changed; the amount of RAM a computer has installed.

Menu Bar - In mouse-based applications, the horizontal strip at the top of the screen that contains menu titles.

Menu - A list of choices.

MIBS (Management Information Bases Systems) - Virtual databases that allow various devices to be monitored using SNMP applications.

Microcell - A bounded physical space in which a number of wireless devices can communicate. Because it is possible to have overlapping cell as well as isolated cells, each device supports wireless standards that establishes the cell boundaries.

Microprocessor - The brain of the computer the processor of information.

MIDI Card - An interface card that lets you use your Apple IIgs as a music synthesizer or as a control device for electronic musical instruments.

MIDI - Stands for Musical Instrument Digital Interface. A software and hardware standard set by the music industry that allows different electronic instruments to communicate with each other and with computers.

MIME Multipurpose Internet Mail Extension - An Internet standard for specifying what happens when a Web browser requests a file with certain characteristics. A file's suffix describes the type of file it is. You determine how you want the server to respond when it receives files with certain suffixes. Each suffix and its associated response make up a MIME type mapping.

MNP 10 EC Protocol - MNP 10EC is an error-correction protocol that is designed for correcting errors that can occur as data is transmitted or received over cellular telephone lines. MNP 10EC provides more efficient error correction than MNP 10.

MNP 10 Protocol - MNP 10 is an error-correction protocol designed to overcome the problems associated with poor telephone line conditions. This protocol is often used for cellular telephone connections. MNP 10 provides less efficient error correction than MNP 10EC.

MNP 4 Protocol - MNP 4 is an error-correction protocol, providing a standard way of correcting errors that can occur as data is transmitted or received. MNP 4 provides less efficient error correction than V.42.

MNP 5 Protocol - MNP 5 is a data-compression protocol, providing a standard way of compressing data for transmission in order to save transfer time. MNP 5 provides less efficient data compression than V.42bis.

Mode - A state that determines the computer's behavior.

Model - An object of the EOModel class that defines, in Entity-Relationship terms, the mapping between enterprise object classes and the database schema. This definition is typically stored in a file created with the EOModeler application. A model also includes the information needed to connect to a particular database server.

Model-View-Controller - An object-oriented programming paradigm in which the functions of an application are separated into the special knowledge Model objects, user interface elements View objects, and the interface that connects them the Controller object.

Modem Server - A combination of hardware and software that enables many people to share a single modem.

Modem - A contraction of modulator-demodulator. A device that enables a computer or terminal to transmit over telephone lines by modulating, or converting, data from a digital to an analog form. When originating a call, a modem modifies its analog carrier signal to carry a digital signal; when answering a call, the modem extracts the digital signal from the modified carrier.

Modifier Track - A track in a movie that modifies the data or presentation of other tracks. For example, a tween track is a modifier track.

Modula-2 - A programming language.

Monitor or Display - Another term for display screen. The term monitor, however, usually refers to the entire box, whereas display screen can mean just the screen. In addition, the term monitor often implies graphics capabilities. You may encounter CRT cathode-ray tube displays, or flat panel displays.

Monitor - In iMovie, the window in the upper-left corner of the screen where clips or the movie can be previewed or played back. Like a television set without channels. It displays instructions from the application to you and shows what you've typed into memory.

Monochrome Monitor - A black-and-white, amber-and-black, or green-and-black monitor.

Mount Point - A string used to identify a live stream, which can be a relayed movie stream, a nonrelayed movie stream, or an MP3 stream. Mount points that describe live movie streams always end with an .sdp extension.

Mouse Button - The button on top of the mouse. You press it to choose from menus or when you want to move items around on the screen.

Mouse - A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction.

Mouse-Based Application - An application that accepts input from a mouse.

MouseText - Special characters, like check marks and little apples, used in mouse-based applications.

Movie - A structure of time-based data that is managed by QuickTime. A QuickTime movie may contain sound, video, animation, or a combination of data types. A QuickTime movie contains one or more tracks; each track represents a single data stream in the movie.

MOV - The Apple QuickTime movie file extension used to name both movie redirect files and actual QuickTime media files.

MP3 (MPEG layer 3) - A popular format for compressing music.

MPEG-4 - An ISO standard based on the QuickTime file format that defines multimedia file and compression formats.

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. There are three major MPEG standards-MPEG-1, MPEG-2 and MPEG-4. The most common implementations of the MPEG-1 standard provide a video resolution of 352-by-240 at 30 frames per second fps. This produces video quality slightly below the quality of conventional VCR videos. MPEG-2 offers resolutions of 720x480 and 1280x720 at 60 fps, with full CD-quality audio. This is sufficient for all the major TV standards. MPEG-2 is used by DVD-ROMs.

MPEG-2 can compress a 2 hour video into a few gigabytes. MPEG-4 is a graphics and video compression algorithm standard that is based on MPEG-1 and MPEG-2 and Apple QuickTime technology.

MS-DOS - The operating system for applications designed to run on IBM and IBM-compatible personal computers.

MTA Mail Transfer Agent - A mail service that sends outgoing mail, receives incoming mail for local recipients, and forwards incoming mail of nonlocal recipients to other MTAs.

Multicast - An efficient, one-to-many form of streaming. Users can join or leave a multicast but cannot otherwise interact with it.

Multihomed - A server with multiple IP addresses.

Multihoming - The ability to support multiple network connections. When more than one connection is available, Mac OS X selects the best connection according to the order specified in Network preferences.

Multipath - The signal variation caused when diffused radio signals take multiple paths from transmitter to receiver.

Multistation Access Unit (MAU) - In a Token Ring network, a lobe or wiring concentrator that physically connects computers and other devices to the ring. Relays in the MAU provide for physical insertion to, and detachment from, the ring.

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

Music Application - An application that can teach you how to read music or help you compose music.

Music Synthesizer - A device that can generate a variety of sounds, including those of traditional musical instruments.

MX Record Mail Exchange Record - An entry in a DNS table that specifies which computer manages mail for an Internet domain. When a mail server has mail to deliver to an Internet domain, the mail server requests the MX record for the domain. The server sends the mail to the computer specified in the MX record.