Introduction: We have already seen how CPU works and also the composition of CPU. We have seen that the CPU takes input from input unit, processes, it and gives the output using output unit. Therefore for working of CPU and its usage, we need a invariable have both input and output devices, which make the CPU’s task useful and help the data processing. The input units and output units should be able to act as a link between the user and the CPU, by input; we mean the data which has to enter to be worked upon. The input has to be given in human under stable form, which is later converted into machine understandable form. The same is the case with output, it has to be human understandable. These input and output units are known as peripheral devices, which are attached to main unit of computer.
Input devices and list of Input Devices with examples
These are those devices which facilitate a user to give input, I.e .data to the CPU to work on. This has to be given n human understandable form, which can be appreciated way of giving the input. There has been a great revolution in the input devices since the time computer was invented, the input devices have become more and more user friendly, so that a user can work very easily without much hassle and with greater speed and accuracy. Let us have a look at various types of devices available and used.
Punched Cards: These input devices were used by Charles Babbage, the “Father of Computer”. These punched cards are rigid pieces of paper which contain rows and columns of numbers. These cards are kept in a punch machine, which makes holes in the cards to represent the data. Later this concept of punched cards were developed by Harmau Holllerith. This method of punched holes representing characters cc cards is popularity known as Hollerith code. This code is interpreted using card Reader, which translates the data on the punched card into machine understandable code, which is then sent to CPU for processes.
The punched card contains 80 columns, containing 12 punching position in each column. The card reader can read these punched cards with speed of about 300-1600 cards per minute. The characters represented are printed on top of card in their respective column to verify the card puncher’s correctness.
Punched card has the following advantages:
It is relatively cheaper.
Both user as well as machine can read data.
The short comings of punched card as input device are:
The volumes of cards which are very huge are difficult to maintain and control.
As the card devices are essentially composed of many mechanical parts, these devices are subjected to frequent breakdowns.
Speed of processing data on card by card reader and punched card is low. ‘
They are not reusable.
Punched Paper Tape: This is a continuous strip of paper on which the characters are represented by using a code which is made of combination of circular holes punched across the width of the paper. As the paper tape id cheaper than punched cards and the speed of paper tape reader being about 100-1000 characters per second, it gained wide using for data communication, recording and requisition.
Magnetic Tape: Magnetic tapes are made if thin plastic coated with magnetic materials like iron oxide which can be magnetized in either of two directions. One polarity is used for representing binary ‘1’ and other for representing ‘0’. These tapes are similar to that of tapes used in audio tape recorders. The data can be easily stored in the binary form along the length of the tape. Magnetic tape drive used to read and also to write data on the magnetic tape. The speed of the magnetic tape drive is about 5000 to 2, 40, 000 characters per second. The advantage of this tape it is can be reused.
Cathode ray Tube/VDU/VDT: These cathode ray tubes are also used as input devices for computers. These are very similar to a picture tube of television. These cathode ray tubes are also known video display unit or video display terminal. These units have a key board for inputting instructions. These units use as on screen blinking dot or dash known as cursor which are used to indicate the input character position.
Keyboards: This is the most common and popular input device. It is similar to the ordinary typewriter with keys for all the characters, numbers, special characters and special functions keys which are assigned special instructions. Using keyboard a user types in the data and instruction, which are usually visible on video display unit? This is easy to work and operate for a user. Key boards usually contain the following keys:
Numeric Keys which are arranged as a pad as same as calculator, which are used for inputting numeric values.
Characters keys which are used for inputting characters.
Functions keys which are preprogrammed for specific operations. These can also be programmed by the user so as to work in a way he desires.
Special keys which are usually used for cursor controls, special symbols and other specific purposes.
Mouse: This input device is used specially for Graphic user Interfaces (GUI). It contains one to three buttons. This is used as a pointed device. The user rolls on a smooth surface, the cursor movement on t he screen is controlled by mouse. One can point to any place on screen, makes selections, click and option etc., so that input is provided to computer. The mouse can be used either individually or in combination with a keyboard so that there is enhancement in input operations. Positioning of cursor using a mouse is easier than typing for non-typists.
Joy Stick: This is one of the popular input device, which is used for playing video games, as the joy stick is moved in the socket, the movements are converted into binary instructions with help of electrical contacts at the base of joy stick. The position and speed with whi
ch the joystick is moved is controlled by a lever. A button is provided at the base, which is usually used to set off explosive pattern of dots, represent firing etc.
Track Ball: This is similar to joy stick, the difference is that track ball uses hard sphere instead of handle for cursor control. This hard ball can be rotated by hand in any direction. The sphere’s speed and direction of rotation is translated digital signals, which control cursor.
Touch Screen: These input devices are very user friendly, which accept the input by mere clicking/pressing with a finger or any other object. These are similar to video display units, which are having the same appearance, the difference being they take input directly. Touch screen input as when a finger or object comes n contact with the screen, the light is broken, and the location of breaking of light beam is recorded, which acts as inputs.
Magnetic Ink Character recognition (MICR): The MICR reader reads the characters which are written using special magnetic ink. These are also human readable. This way of input using magnetic ink is used in banking where the cheque numbers, account number and bans’s identification number are printed using special magnetic ink.
This information is processed using MICR reader, which updates the accounts, does various other processes, programmed for this way of input has several advantages like:
a) In spite of rough handling, one can read the information with a very high degree of accuracy.
b) The information processing is faster.
The major information of MICR is that it can recognize only 10 digits and 4 high characters, we cannot use alphabetic characters.
Magnetic Strips: These are thin bands of magnetically encoded data-These are usually used on credit cards. The data stored on these strips can be anything, but usually they include special codes, which are used for accessing accounts. These strips are usually pasted on the card, and this card is swiped in a card reader which reads the data store on the strips. The data cannot be seen and read by mere looking at the card; there here it is usually secret.
Light Pen: WE usually see, during election analysis, that the anchors of the show, draw lines or markings on the computer screen which we can see, and as well during cricket matches we see various points, fields is pointed or shown Free hand lines. This is done using a light pen. It is a type of a pointed device that is used to choose a displayed menu option on screen for a program. This pen contains a photocell placed in a small tube. As the tip of the pen is moved over the screen surface. It will detect the light corning from a limited field of view. This light from the screen activates photocell and electro response is transmitted to the process which identifies menu option that has triggered photocell. The light pen is used for graphical works, especially computer aided Designed (CAD) process, where user can directly draw on the screen using the light pen. With a keypad attached to a CAD terminal one can select colors, thickness etc, of lines and can even erase lines.
Voice Input/Recognition Devices: The Human need for a easy and faster way of input is giving rise to a very friendly input systems, which take input using human voice, i.e. when one speaks it take the input. These devices are in stage of experimenting and development, where various problems like speech should be in depended of persons, where even the individual’s voice is different, it should take input. This input device uses a microphone which converts human speech into electric signals, which are matches with already existing dictionary of patterns when match is found it gives appropriated output. The great limitation is the vocabulary and modulation, which will surely be overcome and we can get voice response systems.
Optical Recognitions: Unlike MICR, which uses special magnetic ink, here in machine recognition, the device reads a printed surface and translates it into machine understandable firm. The printed surface can be in any ink, it is just scanned into as image and then it is translated and interpreted. Optical recognition devices can be following types:
Optical Mark (sense) Reader (OMR): Here, the card or the form is divided into boxes or ovals, in which a mark is made either by pen or pencil. A character is represented by marking a correct combination of boxes in any column. Usually these cards are printed for special purposes, so that, marking at specific purposes signify number, yes or no etc. This technique is now a day’s popular is various competitive examinations, where the examines have to mark their answers on preprinted answer sheets using pencil, which is then read by on OMR, so that the evaluation becomes easier and accurate. These devices use by any of the methods, one method relies on conductivity of graphite which determines the presence of pencil mark, for this only soft pencil should be used. This residing process of referred as mark sensing. The second method is based on reflectance of light, in which the presence of a mark is indicated by drop in light reflectance of light, in which the presence of a mark is indicated by drop in light reflectance; here marks other than pencil must be used.
Optical Bar Reader (OBR): This is a bit more sophisticated type of optical recognition, where the data is in he form of thin black bars and paces. This is usually seen on the back of some books as well on some products, like greeting cards etc. These lines are known as bar codes or products codes, which are arranged so as to represent data such as name of manufacture, type of product etc.
An optical bar reader recognises and interprets these bars depending on the width of lines, and then the price and product are then matched by the computer.
Optical Character reader (OCR)
This is the most sophisticated optical recognition, which recognises specially shaped numeric and alphabetic characters. It directly reads any printed character and no special ink is required. The flexibility of OCR makes it feasible for organisations to eliminate or reduce the keying in of data. As already seen, a set of optical characters can be used to print merchandise tags, which can be rad using in OCR reader. It is similar in working to a human eye. The basic advantage of OCR is that one need not key in data, into the computer. OCR readers look at each character as if it was mace up of collection of minute spots. Once the total character has been scanned, it is matched with already stored patterns, so that it can interpret data, OCR can read at a speed of about 2400 characters per second. They use varied number and range of fonts. The standard fonts being OCR-A (American Standard), OCR-B ( European-Standard). These devices are usually e
xpensive, but they pay by their ability to take direct inputs into the computer, avoiding data transcription.