0 Fundamental computer

Fundamental computer

computer

Computer is the most versatile electronic machine . A computer is basically a programmable computing machine earlier computers were used for complex computing machine Earlier computer were used for complex computations and used by only scients and engg. . They were only costly and hence only large organization could offord them . The technological break through in design and fabrication of semiconductor devices namely, microcomputers had made it design possible to manufacture powerful nicrocomputer which are with in the reach of small organization and even individuals.

Computer is the versatile electronic machine man has ever created computer have made a great impact on over every day life. Their presence is felt in almost every walk of life be it homes , school, college, office, industries, banks, railway, research and design organization etc.

The word "computer" comes from the word compute that means to calculate so a computer is normally considered to be calculating device  that can perform arithmetic considered to be calculating device that can perform arithmatic operation at an enormous speed . But more accurately . A computer may be defined as a device that operates upon data . Data can be anything like bio data of several applicants when the computer is used to assist us for recuirement personnel. Similarly the data can be the details of passengers such as name , age etc. when the computer is employed for making airline or railway reservations.

A computer cannot only store and process data but also retrieve data i.e take out data from its memory or storage as and when desired. Thus computer is a general term that refers to an electronic data processing machine used for a wide range of activities.  

Characteristics of computer 

The following characteristics depending on their type and use :-

• The ability to perform calculation at a fast that speed.
• The ability to take in information and to store that information for future reterival.
• The ability to use simple logical rules to make decisions for their own internal controls or for the control of some external activity.
• The ability to communicate with other computer system.
• To carry out computation and analysis accurately and speedly. 

Input Devices

There are several types of input devices such as:

Keyboard

 It is the one of the first peripherals used with a computer. Today even keyboard is used as a primary device to enter data. A standard keyboard contain 105 keys and each transmits a special signals . Keyboard keys almost resemble with those of a typewriter . However , computer has got some special keys that help computer perform its operation. 

             We can also classify the keys of keyboard in there type as :-

1. Alphanumeric keys
2. Numeric keys
3. Function keys
4. Special purpose keys

• Alphanumeric keys  = It is centrally located is a keyboard quite like you see in a tradional manual typewriter . The alpha numeric keys include alphabet ( A-2 or a-2),numeric characters (0 to 9), special symbol (!~@#$%^&*=-)can be used by holding shift and numeric keys. Besides alphanumeric and symbol , it has some modifier keys such as Shift , enter, Backspace , tab, ctrl, esc, and alt.  
• Numeric Keypad = It can includes a set of 17 keys containing 0-9 digits , mathematical operators arrow keys and some special keys [home, pg up, pg on, end, ins, enter , and del] , special keys are locked and unlocked , pressing numlock key . It works like a calculator on your computer.
• Function keys = On the upper side of jeyboard there are 12 function keys denoted by f1,f2.........................................................f12. These keys let you use commands in a shortcut manner. Functions of the keys change from software to software. F1 remain for help in most of the softwares commonly used.
• Special purpose keys = With the advent of advanced softwares. Keyboard have been equipped with special keys that work according to now programs in operating system. There are sleep, power, volume, start, shortcut etc.  

Mouse

It is an input device that can be used by single hand by moving a mouse on a plane surface, a ball inside the mouse rolls that in turn moves the rollers in built in the mouse. Mouse has two or more button , left hand side is most in use while right hand side button is used in special cases and special purposes. By the way, we can easily change it with the help of the option available in the operating system software. 

                                                   On pressing the button of mouse we can select the icons on the screen. The pressing of button of mouse by finger is called " clicking" . A mouse is generally used to navigate pointer on the screen and to draw picture and graphics.

        There are three types of mouse such as :

1. Mechanical mouse
2. Optical mouse
3. Cardless mouse 

• Mechanical mouse = This type of mouse that can be commonly used on personal computers. It has a small rubber ball inside the case and roll in all directions. Within the mouse case mechanical sensors preceive the direction tha ball rolls and move the pointer accordingly.
• Optical Mouse = It is a new type of non mechanical mouse. It is quicker but more expensive than the mechanical one. It emits a beam of light from its underside it defects the distance , direction and speed of mouse with its reflection.
• Cardless mouse = In computing, a mouse is a pointing device  that functions by detecting 2 dimentional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons.

Joystick 

The joystick is a pointing device . It is generally used to play games its principal is essentially some as that of the mouse . The joystick has separate sensare to monitor the horizontal and vertical movements Generally, instead of rollers the joystick uses pressure electronic and mechanical potentiometers that very voltage by changing the resistance in an electronic circuit. The basic structure of a joystick comprises of a tube like structure, that can be moved and button . When the joystick is moved or the buttons are pressed or released . The code for the operation is sent to the joystick controller that takes necessary steps to achieve the goal. 

Touch Screen 

Touch screen are input device that enable the user to give input with his fingures. Touch screen touch panels or touch screen panel are display overlays that have the ability to display and receive information on the same screen. The effect of such overlays allows a display to be used as an input device . Removing the keyboard and / or the mouse as the primary input device for interacting with the displays content such display can be attached to computers or as terminals to networks touch screen can also have assisted in recent changes in the PDA and cell phone industries. ATM making these device more usable. 

Graphic Tablet 

A graphic tablet is a compter input device that allow one to hand draw images and graphics . Similar to the way one draws images with a pencil and paper. A graphic tablet consists of flat surface upon that the user may "draw" an image using an attached styles.A pen line drawing apparates. The image generally does not appear on the tablet itself but rather is displayed on the computer moniter.

Track Ball 

It is a pointing device consisting of a ball housed in a socket containing sensors to detect rotation of the ball. The concept of track ball is very similar to that of the mouse . It can be said that the track ball is space saving alternative to the mouse . It is sometimes already intergrated into the keyboard . The structure of the track ball is like an inverted mouse. The ball therefore is visible on top. Instead of moving the ball, the user of a trackball moves the ball itself. Thus the track ball is much larger than a louse ball . The internal structure of the trackball is very similar to that of the mouse.  The track ball can also issues interrepts. The trackball driver provides the same software interface as the mouse.

Card Reader 

Card reader , now a days is used to read smart card , it is also called smart card reader. It is a device like credit card and debit card . It is an electronic memory and is used for different funations medical record , tracking and storing digital fund and controlling identification card are some of the works. Smart card used in big hotel are functioning as key for room locks. card readers reads the stored information in the card , today , card readers can also help in safe online shopping.

Light Pen

The light pen is a pointing device .As the name suggests the light pen is in the form of a pen. The principal behind the working of the light pen is based on the light up of the screen . Light pens do not pass electrical pulses through the cable. Instead, as explained earlier the light pen detects the light up in the screen and its logic determines its location on the screen. The detection of the light up is done with the help of a photo detector located at the tip of the light pen detects the light up. It sends the location of the light up of the computer the contents of the location with the help of the electron scan beam the light pen , inspite of the ease that it provides , has it own limitation .

         Example : because the light pen detects the light up in the screen monitors with low            resolution and sharpness often gives enormous results. In addition , because                      of the user pointing to the monitor with the light pen, the activity tires the human                  arm. 

Output Device

Moniters = It is an output device , where we can get the output on a T.V like screen it is commonly classified as monochrome , Grey scale, color Monitor based on the colors they display.

• Monochrome = It is derived from "mono" that means single and "chrome" means "color" that means single color. Monochrome monitors are single color monitor like a black and white T.V.
• Gray - Scale = Gray scale monitor are special types of monochrome monitors for displaying output in different grey shades. These monitors in flat panel are commonly used in handy computers.
• Color = Monitors can give output as a combination of RGB ( red , green, blue) radiations . Due to RGB concept , they are capable of presenting graphics in a higher resolution. If a computer has a sufficient memory a color monitor can present variety of colors ranging from 16 to 16000000 colors.   

Kinds of monitors

• CRT MONITORS = Almost monitors are based on "picture tube element" as same as a television set , this tube is known as cathode ray tube or crt in short. crt technology is cheaper and capable of presenting high quality colored outputs.
• Flat panel Monitors  = Recently a new technology in the display device has been developed. In this technology charged chemical gases adopt various chemical gases adopt various chemical configuration to create images on the screen.These are called flat panel displays. This device is light in weight and consumes comparitively less electricity. This device is mainly used in laptop computer.

                                                  Flat panel monitors also have lcd technology that means liquid crystal display. LCD technology has less resolution than crt technology , hence clarity of out put is also on the lower side.

         The two more technologies in flat panel display are gas plasma display or grd and electro lumineseent displayor ELD, Both of these technologies VIZ GPD & ELD have better and high quality resolution but these are costlier too. 

How Crt monitor Work

CRT ( cathode ray tube ) monitors consists of a vaccum tube with an electron gun. In a monochrome monitor , a very thin electron bean is shot to wards the plane surface, The internal face of the plane surface has a phosphorous coating on it, that on firing with electron bean emits light that result in the formation of single pixels, it may be possible , a continuous firig of electron beam on a single point may burn phosphorous at that point . To overcome this problem the electron beam is short in such a manner that it travels in 'Z' path and activates the pixels on the screen to present a visual output . The 'Z" type path of electron beam is called "RASTER" .The second type of picture tube i.e called heck directs the path of electron beam by regulating it through magnetic field , when a pixels flashes for a while and extinguishes then a pixel is said to be refereshed .And the rate at which refereshment of a pixels takes place is called referesh rate i.e generally 30 times per second. In case the  referesh rate is low , then screen will flicker it is because phosphorous loses its glow quickly.

         The luminesence of each pixel depends upon the intensity of electron beam that further depends upon voltage of electron current . voltage can easily be regulated . In a digital monitor , presence and absence of voltage can put on and off the pixels respectively . In highly advanced analog brightness of each pixel is controlled by a cotinuous electron beam. In monochrome monitor this technology result in grey scale effects; whereas in colored monitor CRT technology gives more variety of colors than digital monitor.

The CRT of color monitor has some extra components. There are three electron guns separately for red, blue, and green colcurs . There is a triple phosphorous coating on the internal side , so that one pixel can emit three colours red, green, blue and different tints and shades of these colours can also be obtaied by either increasing or decreasing the intensity of electron beam. 

 All CRT does not work on raster graphics ,some modern crt function on vector graphics technology that is high class technology and used to display animation and special graphics on the screen.