Proessing Devices (System Unit)

when you have a conversation with a friend,your ear acts as the input device. It receives the information your friend gives you and passes on yhe information to your brain. Your brainacts as the processing device. It understands the information and frames an appropriate response. The mouth acts as the output device and gives a reply to your friend.

Similarly, in a computer,device, such as the keyboard and the mouse are input devices. The box-like structure called the system unit is responsible for all the processing required  to convert the input to the required output. Devices ,such as the monitor and the printer are output devices. These input and output devices attached to your computer need to conncet to a component within your system unit to allow data to flow. For exemple, the monitor is connected to a video card and the speakers to a sound card. The video card and the the sound card, in turn, reside on the motherboard tofether with the processor, memory and optional internal I/O devices, such as a network interface card.

Motherboard

The system unit contains a large board that has anumber of tiny electronic circuits and other components. It is known as the motherboard. The motherboard is a very important part of the system unit and houses several vital compenents of the computer.

The microprocessor is the the most important component of the motherboard. Data is recived from the input devices. The actual processing of data, that is the arithmetic or logical operations on the giver data,occurs in the microprocessor. Finally, the processed information is the output devices depicts the working of a computer.

Video Card

A video card plugs into a personal computer to give it display capabilities. In other words, it enables your computer to represent data in a visual form. Video cards are also called video adapters, video boards, video display boards, graphics cards and graphics adapters. Each adapter provides digital-to-analog conversion, video RAM and a vider controller so that can be sent to a computer’s display.

Sound card

A sound card is a device in the system unit that enables a computer to accept, process and play sound, A sound card enabl4es the computer to record sound through a microphone. Manipulate sound stored on a disk and output the sound through speakers.

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Storage

Computer storage refers to the data stored in an electromagnetic form to be used by the processor. You can measure the amount of data stored on a computer just as you can measure the amount of ater in container, although measurement units are different, of course. The storage capacity defines the amount of data that can be stored on a storage device.

Computer Data

A computer stores a variety of data and information in its memory,including numbers (0-9), letters (A-Z) and symbols and other characters (#,{},. ‘ ~ ^). A computer uses the binary system to represent these characters. In a binary system, only two digits, 0 and 1, are used. The 0s and 1s in the binary system are known as bits (binary digits). A bit is the smallest unit of measurement of storage capacity. A set of eight bits is called a byte.

NOTE

Kilobytes, megabytes, gigabytes, terabytes are higher  units for mrasureing the capacity of a storage of a storage device.

8 bits                             = 1 byte

1024 bytes                    = 1 kilobyte(KB)

1024 KB                       = 1 megabyte (MB)

1024 MB                      = 1 gigabyte (GB)

 

1024 GB                       = 1 terabyte (TB)

Internet S

torage

Computers use two types of storage: external storage and internal storage. External storage is explained in the  next section. The internal  storage, also called primary storage is the main memory. It stores data and instructions for processing .it also stores the output data temporarily before it is sent to an appropriate output device. The act of retrieving existintg data from memory is called reading out or simiply reading. The process of storing data in memory is called reading  in or writing.

There are two types of internet storage:

1. Random Access Memory (RAM)

2. Read Only Memory (ROM).

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Input/Output devices

There are devices that perform the activities of an input devices in addtition to those of an output device. Such devices are called input/output devices or I/O devices.Modems and network interface cards are examples of input/output devices.

Modem

The term modem stands for modulator-demodulator. Data can be transmitted over different media, such as telephone cables and terrestrial transmission. Telephone cables cab carry waveform called analog signals, analog signals are prone to disturbances from noise and magetic pilses. A relativerly new form of transmission called digital uses binary format (an encoding/decoding system based on 0s and 1s) to send and receive data. This is the format used by computers to send and receive. However, digital signals to cannot be sent through telephone lines. Hence, there is a need to convert the digital signals to analog signals before they are transmitted through telephone cables. Similary, the transmitted data has to be converted to digital signals at the receiving end. A modem is an electronic device used to perform the function of converting the digital signals to analog signals and vice versa.

When you send a massage from  your computer to another computer, the modem acts as an output device. However,when your computer receives a message, the modem acts as an input device. A modem  can be external or internal to the system unit. Modems that are connected to the system unit through cables are called external modems.

Modems are also available as part of system unit. Modems that are built-in to the system unit are called internal modems.

Network interface card

A network interface card (NIC) is a card that is installed in a computer so that it can be connected to a network. Network interface cards provide a dedicated, full-time connection to other computers, for example in a classroom.most network interface cards are designed for a particular type network,although some can serve multiple networks.in classrooms,thmost typical network is Ethernet. Ethernet is a network standard of computer communication using either coaxial or twisted pair cable. Other standards include Tokenring and Framerelay, but these are  less common in classroom environments.

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Output Devices

Any device that is capable of representing informationin a computer is called output device.There are three important output devices connected to the system unit.
 §      Monitor §      Printer
 §      Speakers



Monitor
A monitor resembles a television screen, only with a much higher resolution for better display quality. It is used to display information from the computer. The monitor display text grephics. It typically comes with its own separate power button to turn it on or off.
Printer
A printer is used to transfer data from a computer onto paper. There are colour printers well as grayscale printers available on the market. The fdifferent types of printers are dot matrix printers, inkjet printers and laser printers.
Speakers
Speakers are used to play sound. They may be built in or externally connected to your system. Speakers allow you listen to music and hear sound effects spoken text using your computer. Suppose you want to give a lesson to a group a visually impaired students, you can multimedia presentation. To make the lesson more accessible to these students, you can structure the lesson around an audio componet, thus allowing the students to participate in the lesson using sound rather than relying on the screen presentation.

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INPUT DEVICES

In the input-process-output cycle, input for the process should be provided through a device. Devices  used to provide data and instructions  to the computer are called input devices.Some important computer input devices are listed below.·       Mouse
·       Keyboard
·       Scanner
·       Miccrphone
·       Web camera
 Mouse

A mouse is used to point to and select options displayed on the monitor. It is usually connected to the system unit ny means of a long wire.although wireless mouse devices are also increasingly available. A mouse may have two or three buttons. The left button is the most frequently used button. Newer mouse devices called scroll mouse or wheel mouse come with a wheel between theleft and right buttons. This wheel enables you to smoothly scroll through screens of information. Optical mouse is another advanced pointing device that ises a light emitting component instead of the mouse ball. It detects movement my sensing changes in the light reflected by the light-emitting component. Nowadays, wireless mouse devices are also available.

             When you move theon a flat surface,you will see an arrow moving on the screen correspondingly. This arrow is known as the mouse printerIt is good practice to use a mouse pad instead of just any flat surface. A mouse a small mat with a plastic surface and a rubber or plastic-based cushion on which you can move the mouse. It provides greater traction than smooth surfaces and this makes it easier to move the mouse pointer with greater precision. The mouse ball is likely to glide and not roll on smooth glass or wooden surfaces.KeyboardThe keyboard is used for typing text into the computer.lt is also known as the standard input device. A computer keyboard is similar to that of a typewriter,but it has additional keys as well. The most commonly available computer keyboard has 104 keys.There are different types of keys on the keyboard. The keys are categorized as:§      Alphanumeric keys, including letters and numbers.
§      Punctuation keys, such as the colon (J), the semicolon (;), the question mark (?), single quotes (‘) and double quotes (“)
§      Special Keys, such are, control keys and Function keys  (F1 to F12). There keys have different functions depending on where they are used. For example, the enter key starts a new paragraph in aword processor, but in the command line, it executes a command.
 Function keys are special  keys that are used to perform specific functions. They are labeled as F1 F2 F3 and so on, up to F12. The functionality of the keys differs from software. The function of F1 key in most software is to provide kelp with the software.    Software refers to computer instructions or data that can be stored electronically.ScannerA scanner is used to make an exact copy of a picture or a photograph, For example, if you are a creating a report on an event at your school,you can use scanner to scan photographs or logos and insert them into the report.MicrophoneA microphone is a device used to record sound.Microphones convert sound waves into audio signals.Web CameraA Web Camera is a device capable of converting visuals into digital form. When connected to a computer, iy functions as the eye of the computer. You can use it to take a phototgraph of yourself and store it in the computer or for video conferencing.  

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