Chapter 6 Input and Output DevicesChapter 6 Input and Output Devices

6.1 Input Devices 104

6.2 Output Devices 118

6.1 6.1 Input Devices (1)Input Devices (1)

Input Devices Peripheral devices for entering data, instructions and

user responses Produce machine readable data

Online Operations Data are directly input into the memory of the

computer Offline Operations

Punched cards were prepared with a keypunching machine before they are inputted into the computer

Chapter 6 I/O Devices

6.1 6.1 Input Devices (2)Input Devices (2)

Input devices may be categorised into eight groups: Keyboard Pointing Devices Scanner and Reader Voice Input Digital Camera Video Input Authentication Devices Data-logger

Chapter 6 I/O Devices

6.1.1 6.1.1 Keyboard (1) Keyboard (1)

Standard QWERTY Keyboard Some Extra keys

like arrow key, function keys etc

Enter KeyUse in issuing command

Num-Lock and Insert KeyToggle between 2 states

Special Keys (Shift, Ctrl and Alt) Use with other keys to increase the function of a keyboard

6.1 Input devices

6.1.1 6.1.1 Keyboard Keyboard (2) (2)

Cordless keyboard Data is sent through radio or infrared radiation So, requires a receiver

which is connected to a port on the system unit

Require a battery to operate Non-standard keyboards

Point-of-sales (POS) terminals of supermarkets to speed up data input

Keypads in automatic teller machines (ATM)to limit users to certain keys only

6.1 Input devices

6.1.2 6.1.2 Pointing Devices (1) Pointing Devices (1)

A pointing device An input device Controlling a pointer on the screen

A pointer can be

• an arrow, an I-beam or a pointing hand

Used in Graphical user interface (GUI) clicking buttonsselecting menu itemsmoving the insertion pointselecting textdrawing picturesaccepting handwriting script

• which is later converted into typescript

6.1 Input devices

6.1.2 6.1.2 Pointing DevicesPointing Devices (2) (2)

1. Mouse 2. Trackball 3. Joystick and Wheels 4. Graphic Tablets 5. Touch Screen 6. Touchpad 7. Pointing Stick

6.1 Input devices

6.1.2.1 6.1.2.1 Mouse (1) Mouse (1)

Normally with two buttons and a small wheel Moved under user’s palm

Mechanical mouse Has a ball on its underside A circuit converts movement into electrical signals

Optical mouse Emits light and senses the reflected light to detect the

mouse's movement. Does not require cleaning, but More expensive.

6.1.2 Pointing Devices

6.1.2.1 6.1.2.1 Mouse Mouse (2) (2)

Movement of mouse Relative

The screen pointer moves from its current location.

Work by the point-and-click principle

Cordless mouse Battery-powered Use radio or infrared radiation to communicate with

the system unit

6.1.2 Pointing Devices

6.1.2.2 6.1.2.2 TrackballTrackball

An upside-down mechanical mouse To control the screen pointer, no need to move the

device Rotate the ball with a finger Requires frequent cleaning

6.1.2 Pointing Devices

6.1.2.3 6.1.2.3 Joystick and WheelJoystick and Wheel

Joystick used in computer games consists of a vertical lever mounted on a base and some

buttons The lever allows movement in different directions Buttons activate actions

e.g. jumping and firing.

Wheel Control vehicle in driving simulation software Sometimes include foot pedals for acceleration and braking

actions

6.1.2 Pointing Devices

6.1.2.4 6.1.2.4 Graphic tabletGraphic tablet

also called digitiser flat rectangular electronic board used with a pen or cursor

Movement of the pen Absolute The x-y coordinates of the screen and the graphic tablet

match with each other Handwriting Recognition software

Inputting Chinese characters translate scripts drawn on the screen into character codes

6.1.2 Pointing Devices

6.1.2.5 6.1.2.5 Touch screen Touch screen

Pressure-sensitive display Allows selecting option with fingers Suitable for small amount of data input Examples

Kiosks located in stores, museums and airports Modern pay-phone system uses touch screen to replace physical numeric

keypads

Handheld computers (PDA) and tablet PCWithout keyboard or mouseMainly use pressure-sensitive computer screenHandwriting recognition software translates handwritten letters and

symbols into text

6.1.2 Pointing Devices

6.1.2.6 6.1.2.6 TouchpadTouchpad

Built-in pointing device of some notebook computers Sensitive to pressure and motion With buttons similar to the mouse buttons May tap the touchpad to imitate mouse click

6.1.2 Pointing Devices

6.1.2.7 6.1.2.7 Pointing stickPointing stick

Built-in pointing device of some notebook computers Look like a pencil eraser Located between keys on the keyboard Movement is controlled by a finger

6.1.2 Pointing Devices

6.1.3 6.1.3 Scanners/Reading DevicesScanners/Reading Devices

1. Image Scanner 2. OCR Reader 3. OMR Reader 4. Barcode Reader 5. MICR Reader

6.1 Input Devices

6.1.3.1 6.1.3.1 Image ScannerImage Scanner

Image Scanner Light-sensitive input device Reads printed text and photos by

sending a bright light on the document and detecting the light reflected from the document

Convert the document into digital images

Optical Character Recognition (OCR) Analyse digital images Translate the results into text characters

which can be edited by a word processor

6.1.3 Scanner/Reader

6.1.3.2 6.1.3.2 OCR ReaderOCR Reader

OCR reader range from large machines to handheld wands Some OCR devices can only read the OCR fonts OCR-A is the widely used OCR font

6.1.3 Scanner/Reader

6.1.3.3 6.1.3.3 OMR ReaderOMR Reader

Optical Mark Recognition (OMR) Reader detects pencil mark on paper Commonly used in marking multiple-choice answer

sheets

6.1.3 Scanner/Reader

6.1.3.4 6.1.3.4 Bar code readerBar code reader

Bar code consists of a set of parallel lines and spaces of different

widths is an identification code, commonly used in

libraries, post offices, publishing companies, manufacturers etc.

Bar code readers Highly accurate and fast Printed with the letters that represent the code

for manual input when the bar code cannot be recognised

6.1.3 Scanner/Reader

6.1.3.5 6.1.3.5 MICR ReaderMICR Reader

Magnetic Ink Character Recognition (MICR) Reader Read text printed with magnetised ink Exclusively used by bank for cheque processing

6.1.3 Scanner/Reader

6.1.4 6.1.4 Voice InputVoice Input

Voice input Input data by speaking to a microphone Sound card converts sound waves into digital form

Voice recognition Distinguishes spoken words Matches the input wave patterns with the patterns

stored inside the computer Useful for physically handicapped people

6.1 Input Devices

6.1.5 6.1.5 Digital CameraDigital Camera

Digital Camera Take still pictures Produce bitmap images, e.g. JPG Storing in flash memory/card Transferring to computer through card reader The storage media can be reused

6.1 Input Devices

6.1.6 6.1.6 Video InputVideo Input (1) (1)

1. Video capture card Converts image in analog form into digital form

2. DV camera also called camcorder Records videos as digital signals Signals transmitted directly to a computer or stored in tapes

6.1 Input Devices

6.1.6 6.1.6 Video InputVideo Input (2) (2)

3. Web cam Capture motions and send video signals to computer directly Cannot be used alone (must be used with computer)

Commonly used in videoconferencing.

Videoconferencing allows geographically separated people to meet one another,

via Internet to transmit audio and video data. Besides the videoconferencing software, user need

microphonespeaker andWeb cam/DV camera

6.1 Input Devices

6.1.7 6.1.7 Authentication DevicesAuthentication Devices

Authentication Devices Verify the identity of a user Input the identification code into the computer

1. Magnetic Card Reader

2. Smart Card Reader

3. Fingerprint Scanner

4. Other biometric Devices

6.1 Input Devices

6.1.7.1 6.1.7.1 Magnetic Card ReaderMagnetic Card Reader

Magnetic Card Reader Reads the magnetic stripe on the back of a bank card The magnetic stripe stores the customer's account

number only Updating is done at the bank's computer

6.1.7 Authentication Devices

6.1.7.2 6.1.7.2 Smart Card ReaderSmart Card Reader

Smart Card embedded with a microprocessor and memory Holding much more information than a magnetic card

A smart card can be programmed

If wrong passwords are entered several times, it would be self-destructed

More secure Can be used in financial transactions, like

stored-value ticket for public transport, where it is loaded with digital money

6.1.7 Authentication Devices

6.1.7.3 6.1.7.3 Fingerprint ScannersFingerprint Scanners

Fingerprint Scanners Biometric authentication device Captures curves and indentations of a fingerprint Sends the data into a computer for verification.

Some notebook computer uses this security technique to protect the computer

6.1.7 Authentication Devices

6.1.7.4 6.1.7.4 Other biometric authentication devicesOther biometric authentication devices

Biometric authentication devices Fingerprint Scanner Face Recognition System Hand Geometry Detection Voice Recognition Iris Pattern Matching

6.1.7 Authentication Devices

6.1.8 6.1.8 Data-loggersData-loggers

Data-loggers used in some school laboratories collect and analyse data replace some traditional apparatus Consists of one or more sensors, such as

temperature sensorpressure sensorheartbeat rate sensor

Special data analysis software is needed to display the captured data in digits, tables or graphs

6.1 Input Devices

6.2 6.2 Output DevicesOutput Devices

1. Display Devices 2. Printers 3. Speakers and Headset

Chapter 6 I/O Devices

6.2.1 6.2.1 Display Devices Display Devices (1)(1)

Visual Display Unit (VDU) Most frequently used output device Monitor is a separate unit

Two technologies for VDU: Cathode Ray Tubes (CRT)

Produce images as electrons strike on a fluorescent screenOperate at very high voltageRequire many electronic components.

Liquid Crystal Display (LCD)Thin and light, known as flat-panel displayused in notebook computers, tablet PC, handheld computers and mobile

devices

6.2 Output Devices

6.2.1 6.2.1 Display Devices Display Devices (2)(2)

Display devices Display information visually

Softcopy Data is lost when the machine is powered off

6.2 Output Devices

6.2.2 6.2.2 Display Devices Display Devices (3)(3)

Data projector uses strong light beams to project images on a screen Commonly used in classrooms to facilitate presentation.

Data projectors are of two types: Liquid Crystal Display (LCD) projector Digital Light Processing (DLP) projector

uses tiny mirrors to reflect light, giving brighter, more colourful imagesand usually more durable

6.2 Output Devices

6.2.3 6.2.3 Printers Printers (1)(1)

Printer Printing texts and graphics on paper or other physical

medium, e.g. transparency film Hardcopy

exists physically more permanent than softcopy

Printers can be divided into two types: Impact printers Non-impact printers

6.2 Output Devices

6.2.3 6.2.3 Printers Printers (2)(2)

Printers can be divided into two types: Impact printers

1 Dot Matrix Printer Non-impact printers

2 Inkjet Printer 3 Laser Printer 4 Thermal Printer 5 Plotter/Large Format Printer

6.2 Output Devices

6.2.3.1 6.2.3.1 Dot-matrix PrinterDot-matrix Printer

Dot-matrix printer Typical impact printer Characters are formed by dots:

A matrix of pins strike an inked ribbon against the paper.

Suitable for several layered paper Use continuous-form paper with holes on both sides

Disadvantages Slow and Noisy

6.2.3 Printer

6.2.3.2 6.2.3.2 Ink-jet PrinterInk-jet Printer

Ink-jet printer Non-impact printer Spraying tiny ink drops onto a page High quality and low price

Disadvantages:

1. The ink is soluble

2. Need to wait until the ink is dried completely.

3. Ink left behind will dry out and block the nozzle

4. High running cost (Ink is expensive )

6.2.3 Printer

6.2.3.3 6.2.3.3 激光打印機激光打印機

Laser Printers Non-impact printer Using laser beam to create images onto a drum Similar to photocopying machine Expensive, but Fast, high-quality and low running cost

Colour laser printer Mixing toners of several colours to produce many

different colours

6.2.3 Printer

6.2.3.4 6.2.3.4 Thermal PrintersThermal Printers

Thermal printers are of three types: Direct thermal printer

Direct thermal printer produces images as a Heating a heat-sensitive paperUsed in supermarkets for price labelWill never run out of ink

Thermal wax transfer printer Dye sublimation printer.

Thermal printers are not very popular Consumables (the wax-cartridges and the dyed ribbons)

are quite expensive

6.2.3 Printer

6.2.3.5 6.2.3.5 Plotters/Large-format printersPlotters/Large-format printers

Pen plotter Consists of several colour pens The pens move up and down as the paper rolls Images are drawn by a pen plotter on a paper Mainly used in blueprints, maps and circuit

Large-format printer Larger ink-jet printer Handle paper with widths up to 60 inches Used in producing posters, signs and large drawings

6.2.3 Printer

6.2.3 6.2.3 Speaker and HeadsetsSpeaker and Headsets

Audio output device Enables output from a computer to be heard The two commonly used audio output devices

speakers headsets

Both are connected to the sound card

6.2 Output Devices