Graphical Devices-Mercy

Graphical User Interfaces are typically designed for a specific set of input and output devices. GUI usually built using

toolkits that provide generic intetractive elements such as window, menus, icons, buttons and tabs. GUI

use these graphical elements to offer a consistent visual language to represent

information stored in computer for make it easier to people.

The devices used for input and output determine the nature and capacity of information transferred between human and computer.The terms “input” and “output” are used both as verbs to describe the process of entering or displaying the data, and as nouns referring to the data itself entered into or displayed by the computer.Characteristics of the I/O devices influence user interface design to a large degreeThe choice of an inappropriate or inadequate design will diminish the performance of the taskCombinations of I/O devices can increase the usability of a system

I/O Devices

Input devices are used to convert our information or data into a form which can be understood by the computer. A good input device should provide timely, accurate and useful data to the main memory of the computer.

Input devices(click these links to see respective slides)

Keyboard

Mouse

Touch sensitive pad

Joystick

Light pen

Touch screen

Graphics tablets

Magnetic Strip Reader

Bar Code reader

OCR

MICR

OMR

Voice recognition

Microphone

Scanner

Input sensors

Digital cameras

Web Cameras

Click here to see Advantages and DisadvantagesBack to input devices

A keyboard contains keys that allow a user to enter data and instructions to the computer. All computer keyboards have typing area that includes the letters of the alphabet, numbers, punctuation marks, and other basic keys. Many desktop computer keyboards also have a numeric keypad located on the right side of the keyboard. A standard computer keyboard is called a QWERTY keyboard because of the layout of its typing area which is similar to that of a typewriter.

•Not dependent on a GUI OS.•Using short cuts can be faster than using the mouse.•Most computers come with a keyboard supplied .•People are used to using keyboards to enter data, they need very little training .•A skilled typist can enter data very quickly .•Specialist keyboards are available e.g. ergonomic, gaming keyboards

•When using a keyboard too much, it can cause carpal tunnel syndrome•It is difficult to ex. draw things in graphics programs with a keyboard•It is easy to make mistakes when typing in data •Disabled people often find keyboards difficult to use

A mouse is the most widely used pointing device with a GUI environment on personal computers. A mechanical mouse has a Rubber ball on its underside to detect movement of the mouse. An optical mouse uses devices that emit and sense light to detect the mouse’s movement. A cordless mouse(either optical or mechanical)transmits data using wireless technology such as radio waves or infrared light waves.

Back to input devicesClick here to see Advantages and Disadvantages

A mouse is user-friendly for computer beginners.A mouse is easy and convenient to use with a graphical user interface.Using a mouse to select items or move to a particular position on the screen is faster than using a keyboard.

It is not easy and convenient to input text with a mouse.Issuing commands by using a mouse is slower than by using a keyboard.A mouse is not accurate enough for drawings that require high precision.A mouse usually requires a flat surface to operate.A mouse needs more desk space to operate when compared with a trackball.

Touch pad is a small pressure and motion-sensitive area on a portable computer that you can use to move the mouse pointer. When you move you finger across the pad, the mouse pointer on the screen moves in the same direction. A touch pad is an alternative to a mouse.

Advantages:Easy and fast one finger control.Ideal for portable devices.

Disadvantages:Expensive & found in specific devices (e.g.: Laptop)

Uses •Controlling objects in computer games.•Producing graphics.•Scanners in hospitals.

Used mainly for CAD(Computer Aided Designing) and playing games. 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 user moves the joystick left/right, forward/back and data about these movements are sent to the computer. Small joysticks can also be found on some mobile phones.

A touch screen is an alternative to a separate pointing device. With a touch screen the user selects items on the screen by touching the surface. This makes touch screen systems very intuitive and simple to use.

Often used for information terminals in public places e.g. libraries or museums where mice or keyboards may be stolen or damaged.

                                     A pointing device often used by designers and artists to allow natural hand movements to be input to graphics applications. A stylus is held like a pen and moved over the surface of the tablet. Data about the stylus movements are sent to the computer.

Since it is so like using a pen, it is very easy to create ‘hand-drawn’ sketches.                                     

Graphics Tablet

• Is a short length of magnetic tape stuck on the surface of a tag, card or document.

• On plastic tags or cards the strip is sealed in.• Tags with stripes identify the item they are attached

to.Examples:• On credit card • On bank cards• A phone Card • Cash issue Terminals

Magnetic Strip Reader

• Is set of parallel printed lines of differing thickness, which represent a number.

• The number represented by the bars is also printed above or below the bar code.

• When bar code are used on shop goods, the number coded identifies the product and have following information

1. Country of region 2. Manufacturer 3. An item number for the product.Examples:• Used in Barcodes• Library System • Warehouse stock

Barcodes Readers

Optical Character Recognition (OCR) is a software technology that

can convert images of text into an actual text file that can then be edited, e.g. using word-processing software). The result is just as if the text had been typed in by hand.

OCR is typically used after a page of a book has been scanned. The scanned image of the page is then analyzed by the OCR software which looks for recognizable letter shapes and generates a matching text file.

Advanced OCR software can recognize normal handwriting as well as printed text - this is usually called handwriting recognition.

Optical Character Recognition(OCR)

Characters are printed using an ink containing iron oxide.As the document passes into the reader the ink is magnetized, so that the character shapes can then be recognized electrically.

USES:It is used by banks industry for check processing.Each check contains MICR characters at the lower left edge.These characters represent check number ,bank number and account number.

Branch codeCheque number

Account number

Magnetic ink character reader (MICR)

OMR ScannerOptical Mark Recognition (OMR) is a technology that allows the data from a multiple-choice type form to be read quickly and accurately into a computer.

Special OMR forms are used which have spaces that can be colored in (usually using a pencil). These marks can then be detected by an OMR scanner.

Common uses of OMR are multiple-choice exam answer sheets and lottery number forms.

Voice Recognition

Using a microphone human speech is coded into a sequence of electrical signals.The computer searches a set of stored patterns for the sound which has been input It is now popular for inputting data into word processing or database packages.

ADVANTAGES:Useful for handicapped people with limited movementNo typing or data preparation is necessary.Disadvantage:Few words can be recognized and the error rate is high.Not suitable in noisy places.

Microphone

• Is used for input device for a speech recognition system.

• The voice pattern of user is then converted into instructions to the operating system or application software or text.

• Uses as voice mail messages.

Fax Machines

Scanner

• Read data or information from the source.• Source could be written document, a price

tag, a graphics image , or photograph. • To scan text or images which manipulated in

some way before being printed .

Types of Scanner:•Optical Scanner •Optical Reader

Sensor What it Detects

Temperature Temperature

Light Light / dark

Pressure Pressure (e.g. someone standing on it)

Moisture Dampness / dryness

Water-level How full / empty a container is

Movement Movement nearby

Proximity How close / far something is

Switch or button If something is touching / pressing it

A normal PC has no senses, but we can give it some: We can connect sensors to it...

A sensor is a device that converts a real-world property (e.g. temperature) into data that a computer can process.

A sensor measures a specific property data and sends a signal to the computer.

Digital Camera

• Is used to store, picture in digital form.• Store images using different ways like floppy disk,

memory stick, mini CD ,PC Card and micro device.• Can be connected to a computer easily through USB

port.• Image resolution for digital camera measured by

megapixels.• Higher resolution photo takes up more memory .

Web camera ( Web Cams)

• Is simply a digital camera that is used to capture still images and video images

• These images can then be transmitted to a computer where they are stored in graphics format

• Pictures can be used on the websites

• Camera placed on top the screen such a system allow video conferencing

Output Devices• Output device provide results in a suitable

form after data processing.• Output devices are used to get data out of a

system.• They should be able to do this as accurately

and quickly as possible, and with the minimum of human intervention.

Output Devices

MonitorsPrinterPlotterSpeaker & Headphones

• A monitor is a peripheral device which displays computer output on a screen.

• Most common output deice.• It is known as display screen.• The output display by monitor is called soft copy so it

is ideal for showing the results from an enquire where no printed is needed.

TYPES OF MONITOR:Cathode-ray tube (CRT)

Liquid Crystal Display (LCD or flat-panel)

• This is same type that is use in Television

• Use picture tube technology

• Less expensive than a LCD monitor

• Take up more desk space and use more energy than LCD monitors

• LCD screens are most often seen on portable or laptop computers.• The molecules this substances line up in such a way that the light behind the screens and creates an image.

•Used for notebook computers, PDAs, cellular phones, and personal computers•More expensive than a CRT monitor •Take up less desk space and use less energy than CRT monitors•Types of LCD monitors:

– Passive-matrix LCD– Active-matrix LCD– Gas plasma display– Field emission display

A printer is a peripheral device that produces a physical copy or hard copy of the computer’s output.

It prints character ,symbols and graphics on paper. Print resolution is commonly measured in dots per inch (dpi)

Click here to see types of printer

Impact Printer

• Dot matrix printer • Line printer • Daisy wheel Printer

Non Impact Printer

• Inkjet printer • Laser printer • Thermal printer

• A plotter is a printer that uses a pen that moves over a large revolving sheet of paper.

• It is used in engineering, drafting, map making, and seismology.

An audio device translate audio information from the computer into sounds that people can understand.

Speakers

Headsets