The Motherboard

The motherboard is the largest and most important circuit board in the computer, also called the main board or system board.

 mother board The CPU is located on the motherboard which does most of the processing.

The motherboard is the most complicated piece of equipment inside the computer case. This is because all of the devices connected to the computer must communicate with the CPU on the motherboard, all devices in a computer are either installed directly on the motherboard, or directly linked to it by a cable connected to a port on the motherboard, or indirectly linked to it by expansion cards.

A device which is not directly installed on the motherboard is called peripheral device. the motherboard has some ports which are on the outside of the computer case for devices to connect to it, like a keyboard and mouse, and some ports inside the case to connect devices like floppy disk drives and hard disk drives.

This figure shows the ports which are located on the outside of the computer case.

back motherboard

A keyboard port, a mouse port, a serial port, a parallel port, USB ports, a network port, a 1394 port and three sound ports. The serial port is called that because data is transferred serially (one bit follows the next), this port is often used for an external modem or a serial mouse (a mouse which uses a serial port). A parallel port transmits data in parallel and is used often by a printer. A universal serial bus (USB) port is used by many different input/output devices like printers, keyboards, scanners and digital cameras. A 1394 port (fire wire port) is used for high speed multimedia devices.

Components used primarily for processing:

  • Central processing unit (CPU) is the computers most important chip
  • Chip set which supports the CPU by controlling a lot of the motherboards activities   

Components used for temporary storage:

  • Random access memory (RAM) is used to hold data and instructions as they are processed
  • Cache memory to speed up memory access, depending on the type of CPU

Components which allow the CPU to communicate with other devices:

  • Traces, or wires, on the motherboard used for communication
  • Expansion slots to connect expansion cards to the motherboard
  • The system clock which keeps communication in sync

Electrical system:

  • Power supply connections to provide electricity to the motherboard and expansion cards

Programming and setup data stored on the motherboard:

  • Flash ROM, a memory chip used to permanently store instructions which controls basic hardware functions
  • CMOS setup chip which holds configuration data

Most of the input and output devices are on the outside of the computer case. These devices communicate with components inside the computer case, either by wireless connection or cables attached to the case at a connection called a port. Most of these computer ports are located at the rear of the computer case, although some computer models do have some ports on the front of the case for easier access.


For wireless connections, a wireless device communicates with the computer using a radio wave or infrared port. the most popular of these devices are the keyboard and the mouse, and the most popular output devices are the monitor and the printer.

The keyboard is the main input device of a computer. Standard keyboards today are called enhanced keyboards and hold 104 keys and come in different shapes and sizes, and there are also ergonomic design's making them more comfortable for the hands and wrists.

matias_osx_keyboard mouse

A mouse is a pointing device and is used to move a pointer on the screen and to make selections. The bottom of the mouse has a rotating ball or an optical sensor which tracks movement and controls the location of the pointer on the screen. the buttons on top of the mouse are used for different purposes for different software. For example windows XP uses the left mouse button to execute commands and the right mouse button to display information about the command.

The monitor and the printer are the two most popular output devices.


The monitor is the visual device which displays the main output of the computer. Hardware manufacturers typically rate a monitor according to the size of the screen (in inches) and by the monitor's resolution, which is the function of the number of dots on the screen used for display.

The printer is a very important device, which produces output on paper, this is usually called a hard copy. the most common printers today are the laser and inkjet printers although there are other types of printers available, like the thermal, solid ink and dot matrix printers.

Hardware refers to the computer's physical components, like the monitor, keyboard, memory chips, motherboard and hard drive. Software is the set of instructions which tells the hardware to accomplish a task, software uses hardware for four basic functions: input, processing, storage and output.Hardware components must communicate with both data and instructions among themselves.


A computer user interacts with the computer in a way that the user and the software understand, like entries made from the keyboard and the mouse.


Although, software must convert those instructions into a form which hardware can understand. All of the communication between hardware and software, or between software and other software is reduced to a yes or no, inside the computer this is represented as two simple states: on and off.

The technology of storing and reading only two states is called binary, and the number system which uses only two digits, 0 and 1, is called the binary number system.

A 1 or 0 in this system is called a bit, or a binary digit. Because of the way the number system is organized, grouping is usually done in groups of eight bits, each group is called a byte.

With a computer, all counting and calculations use the binary number system. Counting in binary goes like this: 0, 1, 10, 11, 100, 101, and so on. all letters and characters are converted to a binary code before being stored on in a computer. An example is the uppercase letter A in binary code is 0100 0001, and the number 25 is 0001 1001.


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