The motherboard or mainboard is the main circuit board in a complex electronic system, like a computer. It is the most 'central' part of a computer. All of the different parts of the computer are connected to the motherboard. This lets them work together. In most computers, the motherboard is a big green board, but many come in different colors like black, red and yellow. Electrical parts must be on the motherboard. These parts include transistors and resistors. Major parts that are attached to the board are able to be removed in the future so that they can be upgraded. The CPU is an example of a part that is usually removable. Parts that are not "on-board" can be bought as a card. In fact, many of the on-board parts on today's computers were at one time an expansion card that became very popular. These were put on the board to free up the card slots for other things. Computers today usually have a memory port, 2 or more USB ports, a parallel port (for use with old printers usually), audio & microphone jacks, a network port and ports for the keyboard and mouse.

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