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Input devices and output devices of computer
- 1. Input Devices Introduction:Data and instruction must enter the system before any computations or calculations can be performed and the result of computation be supplied to the outsideworld, thus a computer system must be provided with these communication facilities. Definition : A Device that accepts data from the user.
- 2. Importance of InputDevices To interact with computer user need to rely on an input interfacing technique. This input interfacing is monitored by the input unit of the computer. Input devices read read the user data and insrtuctions and transform them to equivalent internal binary code understood by the computer.
- 3. Types of inputdevices Commandline input (ex: keboard, mouse, scanner) Graphical user input( punched cards, Optical character reader, MICR, Joy stick etc)
- 4. Following aresome of the important input devices which are used in a computer − Keyboard Mouse Joy Stick Light pen Track Ball Scanner Graphic Tablet Microphone Magnetic Ink Card Reader(MICR) Optical Character Reader(OCR) Bar Code Reader Optical Mark Reader(OMR)
- 5. Keyboard Keyboard isthe 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 functions. Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.
- 6. The keyson the keyboard are as follows − 1. Typing Keys These keys include the letter keys (A-Z) and digit keys (09) which generally give the same layout as that of typewriters. 2. Numeric Keypad It is used to enter the numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machines and calculators. 3. Function Keys The twelve function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Each function key has a unique meaning and is used for some specific purpose. 4. Control keys These keys provide cursor and screen control. It includes four directional arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc). 5. Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print
- 7. Advantages of keyboard Keyboard is best suited for character user interface environment. Keyboard can also be used conviently for some graphical input by using shortcut key facility. Dis advantage: Keyboard is not suited for graphical editing work
- 8. Mouse Mouseis the most popular pointing device. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed. It has two buttons called the left and the right button and a wheel is present between the buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer. Advantages: Easy to use Not very expensive
- 9. Joystick Joystickis also a pointing device, which is used to move the cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions. The function of the joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
- 10. Light Pen Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube. When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.
- 11. Track Ball Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved. Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button, or a square.
- 12. Scanner Scanneris an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation. Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed. Types: Flat bed scanner Sheet fed Drum Hand held
- 13. Magnetic InkCard Reader (MICR) MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable. This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR is that it is fast and less error prone.
- 14. Optical CharacterReader (OCR) OCR is an input device used to read a printed text. OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory. OCR are used in credit card billing, to read pin code numbers in post office to sort out mails, OCR are used in other fields like banks, airlines, shipping etc
- 15. Bar CodeReaders Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner. Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to.
- 16. Optical MarkReader (OMR) OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked. It is specially used for checking the answer sheets of examinations having multiple choice questions.
- 17. Output Devices Theoutput devices supply information and results of computation to the outside world in hard copy or soft copy. Following are some of the important output devices used in a computer. Monitors Printer Graphic Plotter Audio output LCD Projector
- 18. Monitors Monitors,commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels. There are two kinds of viewing screen used for monitors. Cathode-Ray Tube (CRT) Flat-Panel Display
- 19. Printers Printeris an output device, which is used to print information on paper. There are two types of printers − Impact Printers Non-Impact Printers Impact Printers Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper. Characteristics of Impact Printers are the following − Very low consumable costs Very noisy Useful for bulk printing due to low cost There is physical contact with the paper to produce an image These printers are of two types − Character printers Line printers
- 20. Character Printers Character printers are the printers which print one character at a time. These are further divided into two types: Dot Matrix Printer(DMP) Daisy Wheel
- 21. Dot MatrixPrinter In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer. Advantages Inexpensive Widely Used Other language characters can be printed Disadvantages Slow Speed Poor Quality
- 22. Daisy Wheel Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality. Advantages More reliable than DMP Better quality Fonts of character can be easily changed Disadvantages Slower than DMP Noisy More expensive than DMP
- 23. Line Printers Line printers are the printers which print one line at a time. These are of two types − Drum Printer Chain Printer
- 24. Drum Printer This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute. Advantages Very high speed Disadvantages Very expensive Characters fonts cannot be changed
- 25. Chain Printer In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters. Advantages Character fonts can easily be changed. Different languages can be used with the same printer. Disadvantages Noisy
- 26. Non-impact Printers Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers. Characteristics of Non-impact Printers Faster than impact printers They are not noisy High quality Supports many fonts and different character size These printers are of two types − Laser Printers Inkjet Printers
- 27. Laser Printers These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page. Advantages Very high speed Very high quality output Good graphics quality Supports many fonts and different character size Disadvantages Expensive
- 28. Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features. They make less noise because no hammering is done and these have many styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.
- 29. Advantages Disadvantages Highquality printing Expensive as the cost per page is high More reliable Slow as compared to laser printer
- 30. Memory Unit: A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address The address of these locations varies from 0 to 65535. Memory is primarily of three types − Cache Memory Primary Memory/Main Memory
- 31. Cache Memory Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. It is used to hold those parts of data and program which are most frequently used by the CPU.
- 32. Advantages Theadvantages of cache memory are as follows − Cache memory is faster than main memory. It consumes less access time as compared to main memory. It stores the program that can be executed within a short period of time. It stores data for temporary use. Disadvantages The disadvantages of cache memory are as follows − Cache memory has limited capacity. It is very expensive.
- 33. Primary Memory(Main Memory) Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off.
- 34. Secondary Memory This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently.
- 35. Characteristics ofSecondary Memory These are magnetic and optical memories. It is known as the backup memory. It is a non-volatile memory. Data is permanently stored even if power is switched off. It is used for storage of data in a computer. Computer may run without the secondary memory. Slower than primary memories.
- 36. Random AccessMemory RAM (Random Access Memory) is the internal memory of the CPU for storing data, program, and program result. It is a read/write memory which stores data until the machine is working. As soon as the machine is switched off, data is erased. RAM is of two types − Static RAM (SRAM) Dynamic RAM (DRAM)
- 37. Computer -Read Only Memory ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture.