What are the basic components of computer? Explain each of given input unit (pointing devices, source data entry devices and keyboard) ,process unit (system unit, microprocessor and its parts, main memory (RAM) and its types ).

What are basic components of computer? 

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A computer has four basic components which are given below. 

1. Input device 

2. System unit 

3. Output unit 

4. Storage device 

Explain each of given input unit (pointing devices, source data entry devices and keyboard), process unit (system unit, microprocessor and its parts, main memory (RAM) and its type). 

Input device or devices are the part of computer by which we give some kind of instructions or data or information to the computer. Which are

1. 
   

   Pointing devices 

Pointing devices are used to control on screen movement include computer mice, touch pads, touch screen, joystick, graphic tablets , and track balls. Some of these devices ,including the mouse and the joystick, can be added to the computer system according to the need of a user. Other devices, such as touch screen, are integrated into specialized computer system designed for particular purpose. 

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Computer mouse 

A computer mouse is a small ,hand held, interacting input device that ,when rolled over a flat surface ,control placement of the curcer on a computer display . A computer mouse is analogous to a live mouse in that it is plame size and mouse shaped ,with rounded corners . Originaly, all mice were connected to the computer with a wire suggestive of a tail; however, cordless mic are also available now. 

A mouse can be a one ,two or three buttons device . After a user position the curser on the computer display by moving the mouse ,screen action can be controlled by single or multiple clicks of the mouse button. Screen icon can be activated with one click , or dragged across the computer display by a single click that is held by the mouse is moved from one location to another .

Touchpads 

Where using a mouse would be awkward ,such as in a laptop computer configuration or cursor movement is more important than character ,touchpads have become popular . These are generally built in to a computer unit, and they often includes clickable buttons that coresponds to the button of the mouse. Beneath the laptop layer of touchpads are tow or more layers separated by a non conducting dielectric; each layer contains a gried of electrod rows and columns. 

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Touch screen 

A touch screen is a computer display screen that is sensitive to the human touch ,allowing the screen to function as an input pointing device. The user touch the screen itself to cause some action to take place .

There are three types of touch screen technology.  A resistive touch screen panel is coated with a thin layer ,metallic, electrically conductive and resistive layer that causes Change in the electrical current that is registered as a touch event and sent to the controller for processing . A surface wave touch screen uses altrasonic waves that pass over the touch screen panel. 

Joysticks 

Joysticks are similar to mice in that they transmit X-Y hand coordinates to the computer to the position a cursor to the screen . A joysticks connected to the joke that pivots freely in all diretions . Sensor detect movement and generate corresponding electric current that are interpreted by a microcontrollor as movement of a cursor.  Later model joysticks also have a "tophat bitten "or contact switch that can be pressed to trigger screen activity . Joysticks are most commonly used in computer games and simulation to provide user with flexibility and quick response time when interacting with on screen events. 

Graphic Tablets 

Digitizing graphic tablets give artists the flexibility to translate precise pen movement into lines on display . They can  also read a user's hand writing through the use of specializad software. Graphic tablets use a variety of technology, including pressure ,sensitive sensor, and capecitive senser ,to determine the location of a pan on the tablets. Some tablets require a use of special type of pen that is attached to the tablets while other allowing the use of any pointed object , including a woden pencil . The resolution and accuracy of a graphic tablets depend on the technology employed.  

Trackballs 

A trackball is a computer cursor control device usually built into the front of the keyboard ,close to the user.  Essentially, the trackball is up side down mouse that rotates in place within a socket . The user first rolls the ball to direct the cursor to the desire place on the screen and then click on one of two buttons near the track ball to select desk top of objects or position the cursor for text entry. 

2. Source data entry devices 

Source data entry devices are devices that creat machine readable data and feed it directly in the computer with out keyboard or mouse. 

Types of source data entry devices 

Scanner 

Scanner is a electronic imaging device that use light sensing equipment to translate images of text, driving and photos into digital form in computers. The resolution refers to the image sharpness and it neasured in dots per inches . The flatbed scanner work like photocopy which the image is place on the glass surface and then scanned and sent to the computer in the form of file. 

Bar cod reader 

Bar cod reader is an electronic device for reading printed barcods usually on a product to know their information which their price . It consists of light source ,a lens and light sensor that translating optical impulses into electrical signals the cod type can be in 1D, 2D, 3D codes regularly vertical strips that can holds up to 16 ASCII character. 2D is different size rectangles that can holds 1000 to 2000 ASCII character . 3D is bumpy code that defferentiates by symbol height and commenly used on metal , hard rubber and other rough surfaces.

Radio Frequency Identification 

RFID works based on an identifying tag bearing a microchip that contains specific code number or data , these code number are read by the radio wave of a scanner linked to a computer data base. Active   RFID tags have their own power source and can transmit signals over a distance to reader device . Passive RFID tag have no battery of their own and must be ready by some sort of scanner . RFID tag of both types are used for a whide range of purpose and are starting to replace bar codes in many situations . The use of RFID is more efficient rather that use bar codes. 

3. Keyboard 

Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter , although there are some additional keys provided for performing additional function . Keyboards are of two sizes 84 keys or 101/102 keys but now keyboard with 104 keys or 108 keys are also available for windows and internet. 

               Process unit  

When we give data to computer then it is possessed by the system unit. 

1. System unit 

The system unit also known as a "tower " or "chassis "is the main part of desktop computers . It includes the mother board, CPU, RAM and other components . The system unit also includes the case that houses the internal components of the computers . The term "system unit " is ophen used to differentiate between the computer and peripheral devices ,such as the monitor, keyboard and mouse . For example, if a repair shop ask you to bring you computer ,it may be unclear whether you need to bring your monitor and peripheral devices as well. If you are told to just bring your system unit it is clear you only need to bring the computer itself. 

2. Microprocessor and its parts 

The microprocessor is mostly used in embedded control application such as house hold applications , automobile and peripheral. It is an integrated electronic circuit that controls all function of CPU , central processing unit, of a computer or other digital device. The entire function of CPU is controlled by a single integrated circuit that accepts binary data as input and process that data according to given instructions then generates the output. This processor contains millions of tiny components like transistors, registers and diodes. 

Components of processor are ;

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ALU (arthematic logic unit), 

Control unit, 

Input-output devices, 

and register array. 

3. Main memory (RAM) and it's types. 

The most important thing is to understand about RAM are that RAM memory is very fast , it can be written to as well as read, it is volatile and finally.  It is very expensive compared to all types of secondary memory in terms of cost per gigabits . It is because of the related high cost of ram compared to secondary memory types that most computer system use both primary and secondary memory. 

There are two types of RAM memory. 

1 DRAM (Pronounced DEE RAM) 

2 SRAM (Pronounced ES RAM)