Input/Output Devices

1.  Input Devices

 Keyboard,Pointing device-mouse, joystick, track ball, touch screen,light pen,scanners,digital camera, bar code reader, , Speech input device (microphone)

Keyboard

It  is  a  text  base  input  device  that  allows  the  user  to  input  alphabets,  numbers  and other characters. It consists of a set of keys mounted on a board.
  

Alphanumeric Keypad

It consists of keys for English alphabets, 0 to 9 numbers, and special characters like + −/ * ( ) etc.

Function Keys

There are twelve function keys labeled F1, F2, F3…  F12. The functions assigned to these  keys  differ  from  one  software  package  to  another.  These  keys  are  also  user programmable keys.

Special-function Keys

These keys have special functions assigned to them  and can be used only for those specific purposes. Functions of some of the important keys are defined below.

Enter

It is similar to the ‘return’ key of the typewriterand is used to execute a command or program.

Spacebar

It is used to enter a space at the current cursor location.

Backspace

This  key  is  used  to  move  the  cursor  one  position  to the  left  and  also  delete  the character in that position.

Delete

It is used to delete the character at the cursor position.

Insert

Insert key is used to toggle between insert and overwrite mode during data entry.

Shift

This key is used to type capital letters when pressed along with an alphabet key. Also used  to  type  the  special  characters  located  on  the  upper-side  of  a  key  that  has  two characters defined on the same key.

Caps Lock

Cap Lock is used to toggle between the capital lockfeatures. When ‘on’, it locks the alphanumeric keypad for capital letters input only.

Tab

Tab is used to move the cursor to the next tab position defined in the document. Also, it is used to insert indentation into a document.

Ctrl

Control key is used in conjunction with other keys to provide additional functionality on the keyboard.

Alt

Also like the control key, Alt key is always used in combination with other keys to perform specific tasks.

Esc

This key is usually used to negate a command. Also used to cancel or abort executing programs.

Numeric Keypad

Numeric  keypad  is  located  on  the  right  side  of  the  keyboard  and  consists  of  keys having numbers (0 to 9) and mathematical operators  (+  −* /) defined on them. This keypad is provided to support quick entry for numeric data.

Cursor Movement Keys

These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down, left, right).

Mouse 

A mouse is a device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction.

History of the Computer Mouse

Invented by Douglas Engelbart of Stanford Research Center in 1963, and pioneered by Xerox in the 1970s, the mouse is one of the great breakthroughs in computer ergonomics because it frees the user to a large extent from using the keyboard. In particular, the mouse is important for graphical user interfaces because you can simply point to options and objects and click a mouse button. Such applications are often called point-and-click programs. The mouse is also useful for graphics programs that allow you to draw pictures by using the mouse like a pen, pencil, or paintbrush.

Mechanical Mouse

Also called as the ball mouse, a mechanical mouse has rubber or metal ball on it’s underside. When the ball rolls, mechanical sensors inside the mouse detect the direction and move the pointer on the screen of the PC. This type of mouse requires a flat surface or a mouse pad to work efficiently. One of the drawbacks of the device is that it is more prone to attracting dust.

Optomechanical or Optical-mechanical Mouse

An Optomechanical or optical-mechanical mouse is same as the mechanical mouse except that the sensors used in it are optical and not mechanical. The device is a combination of optical and mechanical technologies, wherein, the ball is present but the mouse movement is detected optically leading to more accuracy.

Laser Mouse

A laser mouse is the new generation mouse with two necessary components – light emitter and light detector. A laser mouse uses laser as the light emitter and has a precise scanning of mouse movement. You will find a laser mouse ranging anywhere between 1000-5700 dots-per-inch (DPI).

Optical Mouse

An optical mouse also has light emitter and light detector but it uses LED as the light emitter. It generally has lower DPI than laser mouse and users might find difficulty in using the device on black or shiny surfaces.

BlueTrack Mouse

The next generation mouse from Microsoft, it is based on the BlueTrack Technology that enables the mouse to track efficiently on any surface, be it a granite countertop or a carpet. The blue beam in mouse is a combination of image sensor and pixel geometry & is four times larger than the average laser beam used in laser mouse. It generates high-contrast pictures of the surface for an exceptional tracking accuracy.

Mouse Actions

Left Click : Used to select an item.

Double Click : Used to start a program or open a file.

Right Click : Usually used to display a set of commands.

Drag  and  Drop  :  It  allows  you  to  select  and  move  an  item  from  one  location  to another.  To  achieve  this  place  the  cursor  over  an  item  on  the  screen,  click  the  left mouse button and while holding the button down movethe cursor to where you want to place the item, and then release it.

Joystick

The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It typically has a button on top that is  used to select the option pointed by the  cursor.  Joystick  is  used  as  an  input  device  primarily  used  with  video  games, training simulators and controlling robots

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 ball, 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 and a square.

Touchscreen

 is an electronic visual display capable of ‘detecting’ and effectively ‘locating’ a touch over its display area. It is sensitive to the touch of a human finger, hand, pointed finger nail and passive objects like stylus. Users can simply move things on the screen, scroll them, make them bigger and many more.

Ever since then, touchscreen displays are widely used in computers, user interactive machines, public kiosks, point of sale applications, gaming consoles, PDAs, smartphones, tablets, etc.

Types of Touchscreen Technology

1)      Resistive

2)      Capacitive

 Resistive touch

The traditional touch screen technology is analog resistive. Electrical resistance refers to how easily electricity can pass through a material. These panels work by detecting how much the resistance to current changes when a point is touched.

The front surface of resistive touchscreen panel is a scratch-resistant plastic with coating of a conductive material (mostly Indium Tin Oxide, ITO), printed underside.
The second important layer is either made of glass or hard plastic and is also coated with ITO.
Both the layers face each other and are separated with a thin gap in between. An electrical resistance is created between both the layers in such a way that charge runs from top to bottom in one layer and side-to-side in another.
When a finger or stylus tip presses down on the outer surface, both the ITO films meet. It is the measure of the resistance of both the layers at point of contact, which leads to get an accurate measurement of the touch position. The accuracy also relies on the evenness of the coating of ITO on both the layers.

Advantages of Resistive Touchscreen

• Low production cost
• High resistance to dust and water
• Best used with a finger, gloved hand or stylus
• Best suited for handwriting recognition

Disadvantages of Resistive Touchscreen

• Not too sensitive, you have to press down harder
• Poor contrast because of having additional reflections from extra layer of material placed over the screen
• Does not support multi-touch

Capacitive touchscreen

Capacitive touchscreen displays rely on the electrical properties of the human body to detect when and where on a display the user touches. Because of this, capacitive displays can be controlled with very light touches of a finger and generally cannot be used with a mechanical stylus or a gloved hand. Examples of devices with capacitive touchscreens are the Apple iPhone and the T-Mobile G1.

There are mainly three types of perimeter based technologies:

• Infrared Touch Technology – This technology uses beams of infrared lights to detect touch events.
• Surface Acoustic Wave Touch Technology – This type of touch screen uses ultrasonic waves to detect touch events.
• Optical Touch Technology – This type of perimeter based technology uses optical sensors, mainly CMOS sensors to detect touch events.

Digitizing (Graphic) Tablet

Digitizing or Ggraphics’ tablet  is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper. These tablets  may  also  be  used  to  capture  data  of  handwritten  signatures.   Some  tablets  are intended  as  a  general  replacement  for  a  mouse  as  the  primary  pointing  and  navigation device for desktop computers. These are used by architects, engineers and designers in Computer  Aided  Design  (CAD)  for  designing  purposes,  such  as  buildings,  cars, mechanical  parts,  robots  etc.  These are  also  used  in  Geographical  Information  System (GPS) for digitizing of maps.

tablet  is most suited for artists and those who  want the natural feel of a pen-like object  to  manipulate  the  cursor  on  their  screen.  Wacom  is  the  most  well  known manufacturer of graphics tablets, and is incredibly well respected.

  

Light Pens

A Light pen is a pen like light-sensitive device. It is connected by a wire to the computer terminal to detect the CRT beam when pointed towards the screen and generate a narrow electrical pulse that can be fed to the computer as an input signal. It  is  used  to  draw  on  the  screen  or  to  point  to  the  displayed  objects.  It  operates  by detecting the light emitted by the screen phosphors.A light pen can work with any CRT monitor but not with LCD monitors. It is used by architects and engineers for CAD applications and editing
  

Digital Camera

A Digital camera is an electronic device which takes video or still photographs or both, digitally  by  recording  images  via  an  electronic  image  sensor.  Digital  cameras  can  do things which film cameras can’t, for example displaying images on screen immediately after they are recorded.

Optical Mark Recognition (OMR)

OMR  is  the  scanning  of  paper  to  detect  the  presence  or  absence  of  a  mark  in  a predetermined  position.  Now  days,  it  is  used  as  an  input  device  for  source  data  entry purposes.    Universities and colleges often use OMR for the evaluation of OMR sheets for  competitive  exams.  OMR  sheets  consist  of  multiple  choice  question  papers  and students  are  required  to  make  a  mark  to  indicate  their  answers.   OMR  is  used  in  the evaluation of questionnaires, surveys and university exam OMR sheets.

Magnetic Ink Character Recognition (MICR)

Magnetic Ink  Character Recognition is a character recognition system that uses special ink (containing iron oxide)and characters. When a document that contains this ink  needs to be read, it passes through  a  machine,  which  magnetizes  the  ink  and  then  translates  the  magnetic information into characters.

MICR technology  is  used  by  banks  for  faster  processing  of  large  volumes  of  cheques. Numbers  and  characters  found  on  the  bottom  of  checks  (usually  containing  the  check number,  sort  number,  and  account  number)  are  printed  using  Magnetic  Ink.  To  print Magnetic Ink codes, we need a laser printer that accepts MICR toner.

There are two major MICR fonts in use: E-13B and CMC-7.

The 14 characters of the E-13B font. The control characters bracketing each numeral block are (from left to right) transit, on-us, amount, and dash

CMC-7 MICR font. Shown are the 15 characters of the CMC-8 font. The control characters after the numerals are (from left to right) internal, terminator, amount, routing, and an unused character.

A MICR code is unique to each bank branch. Thus, a MICR code can be used to uniquely identify any bank branch. It comprises of 3 parts:

• The first three digits represent the city (City Code). They are aligned with the PIN code we use for postal addresses in India.
• The next 3 digits represent the bank (Bank Code)
• The last 3 digits represent the branch (Branch Code)

Bar Code Reader

A barcode reader is an electronic device which is used to read printed barcodes. Barcodes represent alphanumeric data which is a combination of vertical lines (bars) that vary in width and length. It is a fast and effective way to input data. A Barcode reader uses a laser beam to read the series of thick and thin lines which represent the bar code number.

The bar code is 13 digits long and it has four main divisions. The First two digits of a bar code  represent  the  country,  the  second  part  represents  the  manufacturer’s  code  (five digits) the third part represents the product code (five digits) and the last digit is a check digit.

It may be referred to as linear or one-dimensional (1D). Later they evolved into rectangles, dots, hexagons and other geometric patterns in two dimensions (2D). Although 2D systems use a variety of symbols, they are generally referred to as barcodes as well

Optical Character Reader(OCR)

 It includes the mechanical and electrical conversion of scanned images of handwritten, typewritten text into machine text. It is common method of digitizing printed texts so that they can be electronically searched, stored more compactly, displayed on line, and used in machine processes such as machine translation, text to speech and text mining.
In recent years, OCR (Optical Character Recognition) technology has been applied throughout the entire spectrum of industries, revolutionizing the document management process. OCR has enabled scanned documents to become more than just image files, turning into fully searchable documents with text content that is recognized by computers. With the help of OCR, people no longer need to manually retype important documents when entering them into electronic databases. Instead, OCR extracts relevant information and enters it automatically. The result is accurate, efficient information processing in less time.
Optical character recognition has multiple research areas but the most common areas are as following:

Banking

he uses of OCR vary across different fields. One widely known application is in banking, where OCR is used to process checks without human involvement. A check can be inserted into a machine, the writing on it is scanned instantly, and the correct amount of money is transferred. This technology has nearly been perfected for printed checks, and is fairly accurate for handwritten checks as well, though it occasionally requires manual confirmation. Overall, this reduces wait times in many banks.

Blind and visually impaired persons

One of the major factors in the beginning of research behind the OCR is that scientist want to make a computer or device which could read book to the blind people out loud. On this research scientist made flatbed scanner which is most commonly known to us as document scanner.

Legal department

In the legal industry, there has also been a significant movement to digitize paper documents. In order to save space and eliminate the need to sift through boxes of paper files, documents are being scanned and entered into computer databases. OCR further simplifies the process by making documents text-searchable, so that they are easier to locate and work with once in the database. Legal professionals now have fast, easy access to a huge library of documents in electronic format, which they can find simply by typing in a few keywords.

Retail Industry

Barcode recognition technology is also related to OCR. We see the use of this technology in our common day use.

Other Uses

OCR is widely used in many other fields, including education, finance, and government agencies. OCR has made countless texts available online, saving money for students and allowing knowledge to be shared. Invoice imaging applications are used in many businesses to keep track of financial records and prevent a backlog of payments from piling up. In government agencies and independent organizations, OCR simplifies data collection and analysis, among other processes. As the technology continues to develop, more and more applications are found for OCR technology, including increased use of handwriting recognition.

Electronic Card Reader(ECR)

A card reader is a data input device that reads data from a card-shaped storage medium. The first were punched card readers, which read the paper or cardboard punched cards that were used during the first several decades of the computer industry to store information and programs for computer systems. Modern card readers are electronic devices that can read plastic cards embedded with either a barcode, magnetic strip, computer chip or another storage medium.

A smart card, typically a type of chip card, is a plastic card that contains an embedded computer chip–either a memory or microprocessor type–that stores and transacts data. This data is usually associated with either value, information, or both and is stored and processed within the card's chip

A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called swipe card or magstripe, is read by swiping past a magnetic reading head.

2.  Output Devices

 Monitor , Speaker, Printers ( different types)

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

Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution. It takes more than one illuminated pixel to form whole character, such as the letter ‘e’ in the word help.
A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically. There are some disadvantages of CRT:

• Large in Size
• High power consumption

Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, graphics display.
The flat-panel display is divided into two categories:

• Emissive Displays - The emissive displays are devices that convert electrical energy into light. Example are plasma panel and LED(Light-Emitting Diodes).
• Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD(Liquid-Crystal Device)

Printers

Printer is an output device, which is used to print information on paper.
There are two types of printers:

• Impact Printers
• Non-Impact Printers

Impact Printers

The 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

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

Dot Matrix Printer

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 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 that is why it is called Dot Matrix Printer.
Advantages

• Inexpensive
• Widely Used
• Other language characters can be printed

Disadvantages

• Slow Speed
• Poor Quality

Daisy Wheel

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower name) that is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices which require a few letters to be sent here and there with very nice quality.
Advantages

• More reliable than DMP
• Better quality
• The fonts of character can be easily changed

Disadvantages

• Slower than DMP
• Noisy
• More expensive than DMP

Line Printers

Line printers are the printers which print one line at a time.
These are of further two types

• Drum Printer
• Chain Printer

Drum Printer

This printer is like a drum in shape so it is called drum printer. The surface of drum is divided into number of tracks. Total tracks are equal to size of paper i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on track. The 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

Chain Printer

In this printer, chain of character sets are used so 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

Non-impact Printers

Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Printers.
These printers are of two types

• Laser Printers
• Inkjet Printers

Characteristics of Non-impact Printers

• Faster than impact printers.
• They are not noisy.
• High quality.
• Support many fonts and different character size.

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
• Give good graphics quality
• Support many fonts and different character size

Disadvantages

• Expensive.
• Cannot be used to produce multiple copies of a document in a single printing.

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. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

Advantages

• High quality printing
• More reliable

Disadvantages

• Expensive as cost per page is high
• Slow as compared to laser printer