Function of system unit components and how they communicate.

The main components that comprise the PC are:
· The main system unit
· Storage devices
· Input devices
· Output devices
System Unit: A system unit, also known as a base unit, is the main body of a desktop computer, typically consisting of a metal or (rarely) plastic enclosure containing the motherboard, power supply, cooling fans, internal disk drives, and the memory modules and expansion cards that are plugged into the motherboard, such as video and network cards.
Inside each case there is a main electronic board, called the ‘motherboard’ that houses the CPU, Memory, etc

Motherboard
The main circuit board of a computer. Each motherboard is designed to handle a particular computing processor. 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 screen display, keyboard, and disk drive. All the power, data and addressing information is carried between components on the copper tracks etched on to the printed circuit board.


CPU (Central Processing Unit)
The main chip in any computer system is the Central processing Unit. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system. The CPU itself is an internal component of the computer. Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard. Each motherboard will support only a specific type or range of CPU so you must check the motherboard manufacturer's specifications before attempting to replace or upgrade a CPU. Modern CPUs also have an attached heat sink and small fan that go directly on top of the CPU to help dissipate heat.

Storage devices:
Memory:
The computer has to store the program and data in an area where it can be used by computer’s processor. This area is known as the computer’s memory. Memory consists of computer chips that are capable of storing information.
RAM
Random-access memory is a form of computer data storage. Today it takes the form of integrated circuits that allow the stored data to be accessed in any order.
ROM
Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates).


INPUT DEVICES:
Input devices are used to enter or input data into the CPU. The main input device on computer is the keyboard. There is a wide range of other input devices including the mouse, scanner, communication devices and audio and video capture cards.

Keyboard: A computer keyboard is an important device that allows a computer user to enter characters (e.g. letters and numbers) into a computer. It is the main input device for the computer system. Keyboard is attached with the base unit through a wire which you plug in and start using keyboard.

Mouse:
A small hand controlled device connected to a PC that can be used in a GUI system to move a cursor around the screen. This cursor can be positioned on an icon and the programs associated with that icon can be run by clicking usually the left-hand button on the mouse. The mouse is connected to computer system in similar way as keyboard through a wire, to change basic settings for mouse Control Panel option can be use.

Scanner:
Devices that can read text or illustrations printed on paper and translate the information into a form the computer can use. A type of optical scanner that consists of a flat surface on which you lay documents to be scanned. Flatbed scanners are particularly effective for bound documents.

OUTPUT DEVICES:
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by information processing system.The main output device on a computer system is monitor, printer, speakers etc.

Monitor:
Most programs send the output from their calculation to a screen (apart from those such as payroll programs that send most of their output to the printer, with only a summary going to the screen. The screen is contained in a unit called the ‘monitor’ – sometimes also called the VDU (visual display unit).
There are two main types of monitors.
The CRT monitor, which is big and heavy. It is the oldest technology used by monitors. It looks like a television, but has a bigger resolution and often a higher frequency.
The LCD monitor, which is thin, flat, and lightweight. It is a newer technology than CRTs. The quality can be the same or even better than a CRT.
Monitor is attached with the system through a cable or port which plug in base unit to display on screen.

Printer:
Device that will produce a hard copy of the data that appears on the screen.
A printer is a piece of hardware for a computer. It is an instrument that must be connected to a computer which allows the users to print items on paper, such as letters and pictures. It can also work with Digital Cameras to print directly without the use of a Computer.
Speakers:
The PC speaker is the most primitive sound system used in IBM PC compatibles. It was the only source of sound available to PC games before more technologically advanced sound cards such as AdLib and Sound Blaster were introduced as ISA plug-in cards in the late 1980s.
There is a wire to connect speakers with PC and gets the sound output.

Other Components:
Modem:
Modem is an input and output device Modem (from modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio.

Sound Card: A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to/from a computer under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment (games). Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability. A modern sound card is designed with the PCI interface and connects to the PCI slot of motherboard.

Graphics Card:
Video card, also known as a graphics accelerator card, display adapter, or graphics card, is a hardware component whose function is to generate and output images to a display. It operates on similar principles as a sound card or other peripheral devices.
Most modern graphics cards are AGP based and connects to the AGP bus of the motherboard.


Conclusion:
A system develops by connecting all its components in order with each other that’s how computer works as well. As in above we talked about its components and devices all these devices when attached with the main system unite (base unit) in particular order runs system successfully.