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Human Computer Interface

The Computer

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The Computer : Overview

This section considers the computer system,which is made up of various elements. Each ofthese elements affects the interaction indifferent ways

Input devices - text entry and pointing Output devices - screen, audio

Paper input and output

Memory - RAM, permanent storage media

Processing - speed of processing, networks

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Introduction

The computer is the participant in the interaction thatruns the program

General phrase, encompassing many interactivedevices - light switches, cars, etc

We shall consider mainly the electronic computer

There are two fundamentally different forms ofinteraction

Batch - usually when large quantities of data haveto be read into the machine; Requires little userintervention

Interactive - when the user controls things all thetime

Concentrate on interactive use

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A Typical Computer System

Screen, or monitor, on which there are

Windows - separate areas that behaveindependently

Keyboard

Mouse

These devices dictate the styles ofinteraction that the system supports

If we use different devices, then theinterface will support a different style ofinteraction

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Text Entry Devices: Keyboards

Keypress closes connection, causing acharacter code to be sent

Usually connected by an umbilical cord

Allows rapid entry of text by experienced

users QWERTY arrangement not optimal for typing

layout

Due to typewriters

Other keyboard designs allow faster typing butlarge social base of QWERTY typists producesreluctance to change

Differences between US and UK layouts

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Other Keyboards

Dvorak

Common letters under dominant fingers

Biased towards right hand

Common combinations of letters alternatebetween hands

10-15% improvement in speed andreduction in fatigue

But - large social base of QWERTY typistsproduce market pressures not to change

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Other Keyboards

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DVORAK is better thanQWERTY In typical English, 70% of letters occur in the home row

in Dvorak, compared to 31% in QWERTY.

Finger travel distance is one eighth (1/8) to onetwentieth (1/20) for Dvorak than for QWERTY.

Reaches across rows occur one fifth of the time on

Dvorak than on QWERTY.

The error rate for Dvorak is half that for Dvorak

Cost recovery of retraining

As little as ten days due to increased productivity

Time to achieve 40 words per minute typing speed: 18for Dvorak, 56 for QWERTY

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Other Keyboards

Chord keyboards Only a few keys - four or 5

Letters typed as combination of keypresses

Compact size - ideal for portable applications

Short learning time - keypresses reflect shape ofdesired letter

Fast

But

Social resistance,plus fatigueafter extended use

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Other Keyboards

Maltron (www.maltron.com)

Ergonomic

Mouth

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Hot new interface tech Lightkey virtual keyboard by iBIZ Technology corp.

Concept originally invented for the Israeli Airforcefor use in jet fighter cockpits, didnt prove useful.

Pre-orders ~$99USD .. available in September 04

Size of a (chunky) cigarette lighter

Bluetooth or cable connect to PDA etc.

Cell phone version at end of 2004

No HAPTIC feedback

Poor performance in direct sunlight

Does NOT support touch typing

Audio feedback with each key press

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Other Text Entry Devices

Handwriting recognition Handwritten text can be input into the computer,

using a pen and a digitising tablet Common form of interaction

Problems in

Capturing all useful information - stroke path,pressure, etc. In a natural manner

Segmenting joined up writing into individual letters

Interpreting individual letters

Coping with different styles of handwriting

Handheld organisers being released now thatincorporate handwriting recognition technology anddo away with a bulky keyboard

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Other Text Entry Devices Handwriting recognition

Handwritten text can be input into the computer,using a pen and a digitising tablet

Common form of interaction

Problems in Capturing all useful information - stroke path,

pressure, etc. In a natural manner Segmenting joined up writing into individual letters

Interpreting individual letters

Coping with different styles of handwriting

Handheld organisers and

tablet-PCs incorporatehandwriting recognitiontechnology (eg: graffiti)and do away with keyboard

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Other Text Entry Devices

Speech recognition

Promising, but only successful in limitedsituations -single user, limited vocabularysystems

Problems with External noise interfering

Imprecision of pronunciation

Accents etc

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Positioning and PointingDevices

Mouse

Handheld pointing device

very common

easy to use

Two characteristics planar movement

buttons (usually from 1 to 3 buttons ontop, used for making a selection, indicating

an option, or to initiate drawing etc.)

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Mouse

Movement of mouse, moves screen cursor

Located on desktop

Requires physical space

Relative movement only is detectable

Screen cursor oriented in (x, y) plane; mousemovement in (x, z) plane. So it is an indirectmanipulationdevice

Can lead to hand-eye coordination problems due toindirectness of manipulation

Device itself doesnt obscure screen, is accurate andfast

Some users find it very difficult e.g. arthritis sufferers

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How Does It Work?

Two methods for detecting motion

Mechanical

Optical

Wireless mouse involves a lot less strain on theuser

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Other Positioning Devices

Joystick Indirect device

Takes up very little space

Controlled by either movement (absolute joystick) - position of joystick

corresponds to position of cursor pressure (isometric or velocity-controlled joystick)

-pressure on stick corresponds to velocity of cursorUsually provided with buttons (either on top or on frontlike a trigger) for selection

Does not obscure screen

Inexpensive (often used for computer games, alsobecause they are more familiar to users)

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Other Positioning Devices

Trackball

Bit like an upside-down mouse. Ball isrotated inside static housing, relativemotion moves cursor

Indirect device, fairly accurate. Requiresbuttons for picking. Size and feel oftrackball itself important

Requires little space, becoming popular for

portable and notebook computers

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Other Positioning Devices

Touch-sensitive screen (touch screens)

Detect the presence of finger or stylus onthe screen

Work by interrupting matrix of light beams

or by capacitance changes or ultrasonicreflections

Direct pointing devices

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Other Positioning Devices

Light pen

Digitising Tablet

Cursor keys

Thumb wheels

Keymouse

Dataglove

Eyegaze

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Revolution - the new Nintendocontroller

Resembling a television remote, the unorthodox device uses a sensor totrack movement: players can wave it around like a sword. Described as a"movement capture device", it can detect up, down, left, right, forward andbackward movements. In a promotional video, the wireless controller isused to mimic tennis racquets, musical batons, chopping knives,drumsticks, baseball bats, fishing rods, torches and guns.

Sony has already shown there is a big market for alternative controlmethods with its EyeToy digital camera games that track a player's bodymovements. More than seven million EyeToy games have sold since 2003.Designer Shigeru Miyamoto says: "Sitting in front of your monitor with acontroller, there's nowhere to go from that paradigm - all you can do ismake it prettier and faster. We're going to create a lot of interesting newand creative gaming experiences. We're really focused on creating a homeconsole everyone in the family can enjoy."

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Output Devices

One predominant - the computer screen CRTs, LCD and plasma technologies in use

cheap, fast enough for rapid animation, highcolour capability.

Increased resolution means higher prices

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Concerns with CRTs

Flicker, poor legibility and low contrast can also causeeyestrain and fatigue

Emissions of radiation:

Hints, advantageous to your health:

Do not sit too close to the screen

Do not use very small fonts Do not look at the screen for long periods without a

break

Do not place the screen directly in front of a brightwindow

Work in well-lit surroundings

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Liquid Crystal Displays

Smaller, lighter, with no radiation problems Found on

Portables

Notebooks

Starting to appear more and more on desktops

LCD requires refreshing at usual rates, but slowresponse of crystal means flicker not usually noticeable

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Alternative Output Devices

Visual Analogue representations: dials, gauges,

lights, etc

Head-up displays - found in aircraft cockpits

and Singapore army weapons systems !!! Printers and plotters

Auditory

Beeps, bongs, clonks, whistles and whirrs

Used for error indications and confirmationof actions e.g. keyclick

Speech: not a fully exploited area. Oftenused by visually impaired

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Other input devices

Scanners Can work in colour: shine light at paper and

note intensity of reflection

Resolutions from 100-300 dpi, but available upto 1500 dpi

Used in

Desktop publishing for incorporatingphotographs and other images

Used in document storage and retrievalsystems, doing away with paper storage

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Other input devices

Optical character recognition(OCR)converts bitmap back into text

Different fonts create problems for simpletemplate matching algorithms

More complex systems segment text,decompose it into lines and arcs, anddecipher characters that way

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Limits on InteractivePerformance

Computation bottleneck if processor inadequate fortasks, causing frustration for the user

Storage channel bottleneck moving data from disk tomemory

Graphics bottleneck: updating display requires a lot of

processing power Sometimes helped by adding a graphics co-

processor optimised to take on the burden

Network capacity

Many computers networked - shared resources andfiles, access to printers etc. - but interactiveperformance can be reduced by slow network speed