M

Mainframe
A mainframe is a large-scale computer system. Mainframe computers are powerful and attach to networks and high-speed peripheral devices, such as tape drives, disk drives, and printers.

Media Access Control (MAC)
MAC refers to the method used to gain access or control of a network's physical media (cabling) for sending information across the media. A MAC address is the address of a network interface card (NIC), and is synonymous with the frame address.

Media Access Unit or Multistation Access Unit (MAU)
The definition of MAU depends on the type of LAN involved. In Token Ring, MAU is a multistation access unit. In Ethernet, it is sometimes referred to as a media (or sometimes medium) access unit. MAUs are a type of hub.

Megahertz (Mhz)
One hertz is one cycle of a sine wave per second. One million hertz (MHz) is 1 million cycles per second.

Micro Channel Architecture (MCA)
MCA is IBM's 32-bit internal bus architecture for PCs. MCA was never widely accepted by the PC industry, and was replaced by the PCI bus architecture.

Million (Mega) Bits per Second (Mbps)
Mpbs is used to describe the speed of a communication link. For example, 10 Mbps means that 1,000,000 bits are traveling down a media every second.

Modem
Modem is a contraction for modulator/demodulator. Modems are used to convert binary computer information into signals suitable for transmission across a telephone network.

Modulation
Modulation is the process of modifying the form of a carrier wave (electrical signal) so that it can carry intelligent information on some sort of communications medium. Digital computer signals (baseband) are converted to analog signals for transmission over analog facilities (such as the local loop). The opposite process, converting analog signals back into their original digital state, is referred to as demodulation.

Multicast
Multicast refers to sending information to a group (multiple) of computers at the same time. Similar terms are unicast (sending to one computer) and broadcast (sending to all attached computers).

Multiplexer
A multiplexer is computer equipment that allows multiple signals to travel over the same physical media. Multiple signals are fed into a multiplexer and combined to form one high-speed output stream. This output stream of information consists of all the combined inputs to the multiplexer.