M
* MAC Address
* MAC Layer
* Main Memory
* Mainframe
* Mask Pitch
* Mass Storage
* MATV: Master Antenna TV
* MAU: Media Access Unit
* MBR: Master Boot Record
* MCA: Micro Channel Architecture
* MDF: Main Distribution Frame
* MDI: Medium Dependent Interface
* MDIX: Medium Dependent Interface Crossover
* MDRAM: Multibank DRAM
* Memory
* Memory Address
* Memory Bus
* Memory Stick
* Memory-Mapped I/O
* Merced
* MFP: Multifunction Peripheral
* MIBS: Microprocessor without Interlocked Pipeline Stages
* MICR: Magnetic Ink Character Recognition
* Microcode
* Microcomputer
* Microcontroller
* Micron
* Microprocessor
* MIMD: Multiple Instruction Multiple Data
* Mini Connector
* Minicomputer
* MiniSD Card
* Mips: Millions of Instructions Per Second
* Mirror Site
* Mirroring
* MISD: Multiple Instruction Single Data
* MMC: Multi Media Card
* MMU: Memory Management Unit
* Mobo
* Modem
* Monitor
* Monochrome
* Moore's Law
* MOSFET: Metal-Oxide-Semiconductor Field-Effect Transistor
* Motherboard
* Motion-JPEG
* Mouse
* MPEG: Moving Picture Experts Group
* MPOE: Minimum Point of Entry
* MPP: Massively Parallel Processing
* MRAM: Magnetic RAM
* MSS: Maximum Segment Size
* MTU: Maximum Transmission Unit
* Multifrequency Monitor
* Multihomed
* Multilayer Switching
* Multiplier Lock
* Multi-Processing
* Multiscanning Monitor
* MultiService Switch
MAC address
MAC address, short for Media Access Control address, is a unique hardware address assigned to each network device. In the case of Ethernet, the hardware address is a 48-bit value. To guarantee global uniqueness, the upper 24 bits are controlled by the IEEE, which allocates them to individual device manufacturers.
MAC Layer
MAC Layer, short for Media Access Control Layer, is one of two sublayers that make up the Data Link Layer of the OSI model. The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel.
See a breakdown of the seven OSI layers in the Quick Reference section of Webopedia.
main memory
Main memory, also known as RAM (Radom Access Memory), refers to the internal physical memory of CPU. Computers use RAM to hold the program code and data during execution. One defining characteristic of RAM is that its accesses to different memory locations are almost always completed at about the same speed, in contrast to some other technologies that require a certain delay time for a bit or byte to “come around”.
mainframe
Mainframe is a very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. Modern mainframe computers have abilities not so much defined by their performance capabilities as by their high-quality internal engineering and resulting proven reliability, "expensive" but high-quality technical support, top-notch security, and strict backward compatibility for older software. These machines can and do run successfully for years without interruption, with repairs taking place whilst they continue to run. Mainframe vendors offer such services as off-site redundancy — if a machine does break down, the vendor offers the option to run customers' applications on other machines transparent to end user.
mask pitch
In color monitors, mask pitch is the distance between holes in the shadow mask. The mask pitch is essentially the same as the dot pitch, but it's measured on the mask rather than on the screen. The mask pitch is generally about .30 millimeters (mm). The tighter the mask pitch, the sharper the image.
mass storage
Mass storage refers to various techniques and devices for storing large amounts of data. Mass storage devices include all types of disk drives and tape drives. Mass storage is distinct from memory, which refers to temporary storage areas within the computer. Unlike main memory or RAM, mass storage devices retain data even when the computer is turned off.
MATV: Master Antenna TV
Master Antenna TV (MATV) is a mini cable system relaying the broadcast channels usually to a block of flats or a small housing estate.
MAU: Media Access Unit
A Media Access Unit (MAU, also called Multistation Access Unit, MSAU) is a device to attach multiple network stations in a star topology in a Token Ring network, internally wired to connect the stations into a logical ring. The MAU contains relays to short out nonoperating stations. Multiple MAUs can be connected into a larger ring through their Ring In/Ring Out connectors.
MBR: Master Boot Record
In the IBM PC architecture, the Master Boot Record (MBR), or partition sector, is the 512-byte (½ kibibyte) boot sector, i.e. the sector on the logical beginning of a hard disk that contains the sequence of commands necessary for booting the operating system(s) (OSes).
MCA: Micro Channel Architecture
Micro Channel Architecture (MCA) is a proprietary 16 or 32-bit parallel computer bus created by IBM in the 1980s for use on their PS/2 computers. It is called a bus architecture because it defines how peripheral devices and internal components communicate across the computer's expansion bus. MCA has been replaced by PCI. MCA is no longer used in new computer designs.
MDF: Main Distribution Frame
In telecommunication, Main Distribution Frame (MDF) is a distribution frame on one part of which the external trunk cables entering a facility terminate, and on another part of which the internal user subscriber lines and trunk cabling to any intermediate distribution frames terminate. MDF is a cable rack that interconnects and manages the telecommunications wiring between itself and any number of IDFs (Intermediate distribution frame), which connects internal lines to the MDF. For example, an enterprise that encompasses a building with several floors may have one centralized MDF on the first floor and one IDF on each of the floors that is connected to the MDF.
MDI: Medium Dependent Interface
Medium Dependent Interface (MDI) is an Ethernet port connection that allows network hubs or switches to connect to other hubs or switches without a null-modem, or crossover, cable. In the case of thick coaxial Ethernet, the most commonly used MDI is a type of clamp that is installed directly onto the coaxial cable. For twisted-pair Ethernet, the MDI is an eight-pin connector, which is also referred to as an RJ-45 telephone-style jack. The eight-pin jack provides a connection to the four twisted-pair wires used to carry network signals in the 10-Mbps twisted-pair media system.
MDIX: Medium dependent interface crossover
Medium Dependent Interface Crossover (MDIX or MDI-X), a version of the Medium Dependent Interface (MDI), enables connections between like devices (e.g., two hubs) by crossing the transmit-receive circuits. The straight-through cable connecting an MDI port on one hub or switch is inserted into an MDIX port on the other hub or switch. Both MDI-to-MDI and MDIX-to-MDIX connections use crossover cables. For example, an Ethernet port connection that allows networked end stations (i.e., PCs or workstations) to connect to each other using a null-modem, or crossover cable is an MDIX.
MDRAM: Multibank DRAM
Multibank DRAM (MDRAM), a memory technology developed by MoSys Inc., utilizes small banks of DRAM (32 KB each) in an array, where each bank has its own I/O port that feeds into a common internal bus. Because of this design, data can be read or written to multiple banks simultaneously, which makes it much faster than conventional DRAM.
memory
In the context of computer, memory is the internal storage areas for CPU to access through internal bus. Memory typically comes in the form of chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.
memory address
In computer science, a memory address is a unique identifier for a memory location at which a CPU or other device can store a piece of data for later retrieval. In modern byte-addressable computers, each address identifies a single byte of storage; data too large to be stored in a single byte may reside in multiple bytes occupying a sequence of consecutive addresses. CPU uses the memory address to track where data and instructions are stored in RAM and CPU uses the address bus to communicate which memory address it wants to access, and the memory controller reads the address and then puts the data stored in that memory address back onto the address bus for the CPU to use.
memory bus
The memory bus is the set of wires that is used to carry memory addresses and data to and from the system RAM. The memory bus in most PCs is also shared with the processor bus (or system bus or internal bus), connecting the system memory to the processor and the system chipset. The memory bus is part of the PC's hierarchy of buses, which are high-speed communications channels used within the computer to transfer information between its components.
memory stick
Memory Stick is a removable flash memory card launched by Sony in October 1998, and is also used in general to describe the whole familiy of Memory Sticks. This family includes the Memory Stick Pro, a revision that allows greater maximum storage capacity and faster file transfer speeds, and Memory Stick Duo, a small-form-factor version of the Memory Stick. Typically, a Memory Stick is used as storage media for a portable device, in a form that can easily be removed for access by a PC.
memory-mapped I/O
Memory-mapped I/O (MMIO) is a method of performing input/output between the CPU and I/O devices in a computer. Other methods are Port-mapped I/O (PMIO) or dedicated I/O processors. In MMIP, peripheral control and status registers are mapped into the memory space rather than the I/O space. From the software developer's point of view, memory-mapped I/O devices look very much like memory devices. Their registers can even be accessed via ordinary pointers and data structures, greatly simplifying device driver implementation.
Merced
Merced is the code name for a 64-bit microprocessor, Itanium, developed jointly by Intel and HP. Itanium is based on the Intel Architecture-64 (IA-64) which employs microprocessor techniques such as long instruction words (LIW), instruction predication, branch elimination, and speculative loading.
MFP: Multifunction Peripheral
Multifunction Peripheral (MFP), also known as Multi Function Product/Device, is a single device that serves several functions, for example, multi-finctional printer. Typically, multifunction printers can act as a printer, a scanner, a fax machine and a photocopier. These devices are becoming a popular option for SOHO users because they're less expensive and occupy less space than buying three or four separate devices.
MIBS: Microprocessor without Interlocked Pipeline Stages
Microprocessor without Interlocked Pipeline Stages (MIPS) is a Reduced Instruction Set Computer (RISC) microprocessor architecture developed by MIPS Technologies. The early MIPS architectures were 32-bit implementations (generally 32-bit wide registers and data paths), while later versions were 64-bit implementations. MIPS designs are used in SGI's computer product line; many embedded systems; Windows CE devices; Cisco routers; and video game consoles like the Nintendo 64 and Sony PlayStation, PlayStation 2, and PlayStation Portable handheld system.
MICR: Magnetic Ink Character Recognition
Magnetic Ink Character Recognition(MICR) is a technique that enables special characters printed in magnetic ink to be read and input rapidly to a computer. When a document that contains this ink needs to be read, it passes through a machine, which magnetizes the ink and then translates the magnetic information into characters. MICR is used to verify the legitimacy or originality of paper documents, especially checks. MICR is used extensively in banking because magnetic-ink characters are difficult to forge and are therefore ideal for marking and identifying cheques.
microcode
Microcode, also known as microprogram, refers to the instruction set of a CPU as a sequence of microcode instructions (microinstructions), each of which typically consists of a number of bit fields and the address of the next micro-instruction to execute. Micro-code is the translation layer between machine instructions and the elementary operations of a computer. Micro-code is stored in ROM and allows the addition of new machine instructions without requiring that they be designed into electronic circuits when new instructions are needed. Several micro-instructions will usually be required to fetch, decode and execute each machine code instruction. The elements composing the micro-program/micro-code exist on a lower conceptual level than the more familiar assembler instructions. Each element is differentiated by the "micro" prefix to avoid confusion: micro-program, micro-code, micro-instruction, micro-assembler, etc.
microcomputer
A microcomputer generally refers to a computer with a microprocessor (µP) as its CPU. Another general characteristic of these computers is that they occupy physically small amounts of space. Desktop computers, video game consoles, laptop computers, tablet PCs, and many types of handheld devices may all be considered examples of microcomputers according to this technical definition.
microcontroller
Microcontroller is a computer-on-a-chip optimised to control electronic devices. It is designed specifically for specific tasks such as controling a specific system, in contrast to a general-purpose microprocessor, the kind used in a PC. A typical microcontroller contains an integrated CPU, all the memory and I/O interfaces needed on the same chip, whereas a general purpose microprocessor requires additional chips to provide these necessary functions. Examples of microcontrollers are Microchip's PIC, the 8051, Intel's 80196, and Motorola's 68HCxx series.
Micron
Micron is a unit of length measurement that is equal to 1/1000 of one millimeter or 1/25000 of an inch. Cladding and core of fiber optics are measured with this unit.
microprocessor
A microprocessor (abbreviated as µP or uP) is a computer electronic component made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (microchip or just chip). The central processing unit (CPU) is the most well known microprocessor, but many other components in a computer have them, such as the GPU on a video card. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.
MIMD: Multiple Instruction Multiple Data
Multiple Instruction Multiple Data (MIMD) is a type of parallel computing architecture where many functional units perform different operations on different data. Examples would be a multiprocessor or transputer computer, or a network of workstations.
Mini Connector
Mini Connector refers to a physical connector utilized for PC and telecommunication hardware-interface applications.
minicomputer
Minicomputer is a largely obsolete term for a class of multi-user computers which make up the middle range of the computing spectrum, in between the largest multi-user systems (mainframe computers) and the smallest single-user systems (microcomputers or personal computers). More modern terms for such machines include midrange systems (common in IBM parlance), workstations (common in Sun Microsystems and general UNIX/Linux parlance), and servers.
MiniSD Card
The miniSD card was adopted in 2003 by the SD Association as an ultra-small form factor extension to the SD card (Secure Digital Card) standard. While the miniSD card were designed especially for use in mobile phones, they are packaged with a miniSD adapter which enables compatibility with all devices equipped with a standard SD Memory Card slot. The MiniSD Card provides the same benefits as the SD Card, but is smaller than the original SD Card. miniSD Cards are typically found in many mobile phones with features such as built-in digital cameras, downloading and games. MiniSD cards are 21.5 x 20 x 1.4 mm and generally provide 16MB to 256MB of storage.
Mips: Millions of Instructions Per Second
Millions of instructions per second (Mips) is the number of instructions executed by a processor per second. Mips is a measure of the processing speed of a micro processor.
Mirror site
Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads. Mirroring is a one-way operation whereas file synchronization is two-way. On the Internet, a mirror site is an exact copy of another Internet site (a web site or database).
Mirroring
In computer industry, mirroring is a data duplicate technique used to provide higher availability of computer data. On the Internet, a mirror site is an exact copy of another Internet site (often a web site).
MISD: Multiple Instruction Single Data
Multiple Instruction Single Data (MISD) is a type of parallel computing architecture where many functional units perform different operations on the same data. Pipeline architectures belong to this type, though a purist might say that the data is different after processing by each stage in the pipeline. Not many instantiations of this architecture exist, as MIMD and SIMD are often more appropriate for common data parallel techniques. Specifically, they allow better scaling and use of computational resources than MISD does.
MMC: Multi Media Card
The Multi Media Card (MMC) is a flash memory card standard. Unveiled in 1997 by Siemens AG and SanDisk, it is based on Toshiba's NAND-based flash memory, and is therefore much smaller than earlier systems based on Intel NOR-based memory such as Compact Flash. MMC is about the size of a postage stamp: 24mm x 32mm x 1.5mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow transfers of 4 or sometimes even 8 bits at a time. They have been more or less superseded by Secure Digital cards, but still see significant uses because MMC cards can be used in any device which supports SD cards.
MMU: Memory Management Unit
Memory Management Unit (MMU) is the hardware component that manages virtual memory systems. Among the functions of such devices are the translation of virtual addresses to physical addresses, memory protection, cache control, bus arbitration, and, in simpler computer architectures, bank switching. Typically, the MMU is part of the CPU, though in some designs it is a separate chip. The MMU includes a small amount of memory that holds a table matching virtual addresses to physical addresses. This table is called the Translation Look-aside Buffer (TLB). All requests for data are sent to the MMU, which determines whether the data is in RAM or needs to be fetched from the mass storage device. If the data is not in memory, the MMU issues a page fault interrupt.
mobo
MOBO is a nickname for motherboard, which is the central or primary circuit board making up a complex electronic system, such as a computer. The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive. Collectively, all these chips that reside on the motherboard are known as the motherboard's chipset.
modem
Modem, a word constructed from modulator and demodulator, is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. Modem translates information between analog and digital world.
monitor
Monitor, also known as display screen, is a computer peripheral device capable of showing still or moving images generated by a computer and processed by a graphics card. Monitors generally conform to one or more display standards. Once an essential component of a computer terminal, computer displays have long since become standardized peripherals in their own right.
monochrome
Monochrome basically means one color. In computing, monochrome has two meanings: it can mean having only one colour which is either on or off, or also allowing shades of that colour, although the latter is more correctly known as greyscale. Monitors, for example, can be monochrome, grayscale or color. Monochrome monitors actually use two colors, one for the display image (the foreground) and one for the background. Graphic images can also be monochrome, grayscale, or color.
Moore's Law
Moore's Law, an experience formular made in 1965 by Gordon Moore (co-founder of Intel), states of the doubling of the number of transistors on integrated circuits (a rough measure of computer processing power) every 18 months. Moore's original statement can be found in his publication "Cramming more components onto integrated circuits", Electronics Magazine 19 April 1965: "The complexity for minimum component costs has increased at a rate of roughly a factor of two per year ...".
MOSFET: Metal-Oxide-Semiconductor Field-Effect Transistor
Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is a field effect transistor in both digital and analog circuits. The MOSFET is composed of a channel of n-type or p-type semiconductor material, and is accordingly called an NMOSFET or a PMOSFET. The width of the channel, which determines how well the device conducts, is controlled by an electrode called the gate, separated from channel by a thin layer of oxide insulation. The insulation keeps current from flowing between the gate and channel. IGFET is a related term meaning Insulated-Gate Field-Effect Transistor, and is almost synonymous with "MOSFET", though it can refer to FETs with a gate insulator that is not oxide.
motherboard
A motherboard, also known as a main board, mainboard, logic board or system board, and sometimes abbreviated as mobo, is the central or primary circuit board making up a complex electronic system, such as a computer. The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive. Collectively, all these chips that reside on the motherboard are known as the motherboard's chipset.
motion-JPEG
Motion JPEG (M-JPEG) is a video codec where each video field is separately compressed into a JPEG image. The resulting quality of intraframe video compression is independent from the motion in the image which differs from MPEG video where quality often decreases when footage contains lots of movement. In addition, it makes video editing easier, as cuts may begin on any frame, not only on the beginning of a group of frames. JPEG (Joint Photographic Experts Group) is a standard for storing and compressing digital images. Motion-JPEG extends this standard by supporting videos. In motion-JPEG, each frame in the video is stored with the JPEG format.
mouse
A mouse is a handheld pointing device for computers to control the movement of the cursor or pointer on a display screen. 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.
MPEG: Moving Picture Experts Group
Moving Picture Experts Group (MPEG) is the family of digital video compression standards and file formats developed by a working group of ISO. MPEG generally produces better-quality video than competing formats, such as Video for Windows, Indeo and QuickTime. MPEG files can be decoded by special hardware or by software.
MPOE : Minimum point of entry
Minimum point of entry (MPOE) is the location where a telecommunications provider's wiring crosses or enters a building.
MPP: Massively parallel processing
Massively parallel processing (MPP) is a type of computing that uses many separate CPUs running in parallel to execute a single program. Systems with thousands of such processors are known as massively parallel. There are many different kinds of parallel computers (or "parallel processors") depending on how the processors are interconnected and how the processors communicate with memories, or if all processors execute the same instructions at the same time (single instruction/multiple data -- SIMD) or each processor executes different instructions (multiple instruction/multiple data -- MIMD). Parallel processor machines are also divided into symmetric and asymmetric multiprocessors, depending on whether all the processors are capable of running all the operating system code and, say, accessing I/O devices or if some processors are more or less privileged.
MRAM: Magnetic RAM
Magnetoresistive RAM (MRAM), also known as magnetic RAM, uses magnetic charges to store data instead of electric charges, such as those used in SRAM and DRAM technologies.
MRAM as memory technology can retain data even when the power is turned off and only requires a small amount of electricity to store data bits.
MSS: Maximum Segment Size
Maximum Segment Size (MSS) is the largest amount of data, specified in bytes, that a computer or communications device can handle in a single, unfragmented piece. The MSS is an important consideration in Internet connections, particularly web browsing. When the Internet's Transmission Control Protocol (TCP) is used to achieve an Internet connection, the computers being connected must each agree on, and then set, the MTU size acceptable to both.
MTU: Maximum Transmission Unit
Maximum Transmission Unit (MTU) is the largest physical packet size in bytes that can be passed by a layer of a communications protocol. A MTU parameter is usually associated with a communications interface (NIC, serial port, etc.). Each type of networks may have different size of MTU. The MTU for Ethernet is 1500 bytes. Higher-level network protocols like TCP/IP can be configured with a maximum packet size, but this setting is distinct from the physical MTU. Any messages larger than the MTU are divided into smaller packets before being sent. The MTU of a network has important implications on the performance of computer communications because that too large an MTU size may mean retransmissions if the packet encounters a router that can't handle that large a packet, and too small an MTU size means relatively more header overhead and more acknowledgements that have to be sent and handled.
Multifrequency monitor
Multifrequency monitor is a type of monitor capable of accepting signals at more than one frequency. Multifrequency monitors can support only a select number of frequency levels.
Multihomed
Multihomed indicates a host connected to two or more networks or having two or more network addresses. For example, a network server may be connected to a serial line and a LAN or to multiple LANs. Multihoming is a technique often used to increase the reliability of the internet connection of an IP network. It is typically used to describe to a customer, rather than an internet service provider (ISP) network.
Multilayer switching
Multilayer switching is simply the combination of traditional Layer 2 switching with Layer 3 routing in a single product. Multilayer switching is new, and there is no industry standard yet on nomenclature. Vendors, analysts, and editors don't agree about the specific meaning of terms such as multilayer switch, Layer 2 router, Layer 3 switch, IP switch, routing switch, switching router, and wirespeed router. The term multilayer switch seems to be the best and most widely used description of this class of product that performs both Layer 3 routing and Layer 2 switching functions.
Multiplier lock
The multiplier lock is a feature built into a CPU chip that prevents it from being overclocked. It is used by CPU manufacturers to prevent consumers and dealers from overclocking the CPU. When locked, the multiplier--the factor by which the bus speed is multiplied to derive the CPU speed--is stuck at one given value, thus ruling out any overclocking on motherboards strictly built to the CPU manufacturers specifications. The lock is hard wired into the CPU and is very difficult to overcome.
Multi-Processing
Multi-processing typically refers to the use of more than one processor (CPU) in a single computer system. So-called multi-processor systems usually have a common memory space through which all of the processors can communicate and share data. Multi-processing sometimes refers to the execution of multiple concurrent software processes in a system as opposed to a single process at any one instant.
Multiscanning monitor
Multiscanning monitor is a type of monitor that automatically adjusts to the signal frequency of the video display board to which it is connected. Multiscanning monitors can display images based on almost any graphics display system, including MDA, Hercules, EGA, VGA, and SVGA. Multiscanning monitors can support video signals at any frequency level within its range.
MultiService Switch
MultiService Switch is a type of network switch that can provide switching to data as well as voice and video. It is a network device designed for the converged network of multiple services.