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18 cse366t human computer interaction - hci - unit i
1. 4/6/2022 SRM University Ramapuram 1
8/22/2011
School of Computing, Department of IT 1
Human Computer
Interaction – 18CSE366T
UNIT - I
Mrs. S. Babeetha
AP(Sr.G)
SRMIST, Ramapuram
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the human
1. Human Computer Interaction by Alan Dix, Janet Finlay,
Gregory D.Abowd and Russell Beale – Third Edition - Pearson
Education – 2004
2. Human Computer Interaction by K.Meena and R.Sivakumar –
2015 – Prentice Hall India
3. Designing the User Interface: Strategies for Effective Human
Computer Interaction by Ben Shneiderman and Catherine
Plaisant – Fifth Edition - 2009 – Pearson Addison Wesley
4. Designing Web Interfaces by Bill Scott and Theresa Neil –
First Edition – O‘Reilly Media Inc. – 2009
5. Mobile Design and Development by Brian Fling - First Edition
– O‘Reilly Media Inc. – 2009
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• Human Computer interaction (HCI) is characterized as a dialogue or
interchange between the human and the computer because the
output of one serves as the input for the other in an exchange of
actions and intentions.
• HCI is the study of interaction between people (users) and
computers.
• Human Computer Interaction is concerned with the design,
evaluation and implementation of interactive computing systems for
human use and with the study of major phenomena surrounding
them.
• Human Computer Interaction (HCI) is an interdisciplinary field in
which computer scientists, engineers, psychologists, social scientists
and design professional play important roles.
Human Computer Interaction (HCI)
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• HCI tackles questions concerning how people interact with
computers
• ◦ Are computers intuitive or complicated?
• ◦ Are computers rewarding or frustrating?
• ◦ How can computers be made accessible to everybody (e.g.
different physical abilities, different languages etc.)?
• ◦ To what level can computer interaction be standardized?
• ◦ Are computers “user-friendly”?
• ◦ What does it mean to be “user-friendly”?
Introduction
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• The goal of HCI is to improve the interaction between users and
computers by making computers more user- friendly and
receptive to the user's needs.
• Interacting with technology is cognitive.
• Human information processing referred to as cognition
• Human cognition process is involved when interacting with
system, like attention, perception and recognition, memory,
learning, reasoning, problem solving and decision making.
• Need to take into account cognitive processes involved and
cognitive limitations of users.
• Provides knowledge about what users can and cannot be
expected to do.
Introduction
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Information i/o …
visual, auditory, haptic, movement
Information stored in memory
sensory, short-term, long-term
Information processed and applied
reasoning, problem solving, skill, error
Emotion influences human capabilities
Each person is different
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Two stages in vision
• physical reception of stimulus
• processing and interpretation of stimulus
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mechanism for receiving light and
transforming it into electrical energy
light reflects from objects
images are focused upside-down on retina
retina contains rods for low light vision
and cones for colour vision
ganglion cells (brain!) detect pattern and
movement
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Size and depth
visual angle indicates how much of view object
occupies
(relates to size and distance from eye)
visual acuity is ability to perceive detail (limited)
familiar objects perceived as constant size
(in spite of changes in visual angle when far away)
cues like overlapping help perception of size
and depth
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Brightness
subjective reaction to levels of light
affected by luminance of object
measured by just noticeable difference
visual acuity increases with luminance as does flicker
Colour
made up of hue, intensity, saturation
cones sensitive to colour wavelengths
blue acuity is lowest
8% males and 1% females colour blind
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The visual system compensates for:
movement
changes in luminance
Context is used to resolve ambiguity
Optical illusions sometimes occur due to
over compensation
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Several stages:
visual pattern perceived
decoded using internal representation of language
interpreted using knowledge of syntax, semantics,
pragmatics
Reading involves saccades and fixations
Perception occurs during fixations
Word shape is important to recognition
Negative contrast improves reading from
computer screen
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Provides information about environment:
distances, directions, objects etc.
Physical apparatus:
outer ear – protects inner and amplifies sound
middle ear – transmits sound waves as
vibrations to inner ear
inner ear – chemical transmitters are released
and cause impulses in auditory nerve
Sound
pitch – sound frequency
loudness – amplitude
timbre – type or quality
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Humans can hear frequencies from 20Hz to
15kHz
less accurate distinguishing high frequencies than
low.
Auditory system filters sounds
can attend to sounds over background noise.
for example, the cocktail party phenomenon
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Provides important feedback about environment.
May be key sense for someone who is visually
impaired.
Stimulus received via receptors in the skin:
thermoreceptors – heat and cold
nociceptors – pain
mechanoreceptors – pressure
(some instant, some continuous)
Some areas more sensitive than others e.g. fingers.
Kinethesis - awareness of body position
affects comfort and performance
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Time taken to respond to stimulus:
reaction time + movement time
Movement time dependent on age, fitness
etc.
Reaction time - dependent on stimulus type:
visual ~ 200ms
auditory ~ 150 ms
pain ~ 700ms
Increasing reaction time decreases accuracy
in the unskilled operator but not in the skilled
operator.
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Fitts' Law describes the time taken to hit a
screen target:
Mt = a + b log2(D/S + 1)
where: a and b are empirically determined constants
Mt is movement time
D is Distance
S is Size of target
targets as large as possible
distances as small as possible
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There are three types of memory function:
Sensory memories
Short-term memory or working memory
Long-term memory
Selection of stimuli governed by level of arousal.
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Buffers for stimuli received through senses
iconic memory: visual stimuli
echoic memory: aural stimuli
haptic memory: tactile stimuli
Examples
“sparkler” trail
stereo sound
Continuously overwritten
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Repository for all our knowledge
slow access ~ 1/10 second
slow decay, if any
huge or unlimited capacity
Two types
episodic – serial memory of events
semantic – structured memory of facts,concepts, skills
semantic LTM derived from episodic LTM
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Semantic memory structure
provides access to information
represents relationships between bits of information
supports inference
Model: semantic network
inheritance – child nodes inherit properties of parent
nodes
relationships between bits of information explicit
supports inference through inheritance
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Information organized in data structures
Slots in structure instantiated with values for
instance of data
Type–subtype relationships
DOG
Fixed
legs: 4
Default
diet: carniverous
sound: bark
Variable
size:
colour
COLLIE
Fixed
breed of: DOG
type: sheepdog
Default
size: 65 cm
Variable
colour
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Model of stereotypical information required to interpret situation
Script has elements that can be instantiated with values for context
Script for a visit to the vet
Entry conditions: dog ill
vet open
owner has money
Result: dog better
owner poorer
vet richer
Props: examination table
medicine
instruments
Roles: vet examines
diagnoses
treats
owner brings dog in
pays
takes dog out
Scenes: arriving at reception
waiting in room
examination
paying
Tracks: dog needs medicine
dog needs operation
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Representation of procedural knowledge.
Condition/action rules
if condition is matched
then use rule to determine action.
IF dog is wagging tail
THEN pat dog
IF dog is growling
THEN run away
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rehearsal
information moves from STM to LTM
total time hypothesis
amount retained proportional to rehearsal time
distribution of practice effect
optimized by spreading learning over time
structure, meaning and familiarity
information easier to remember
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decay
information is lost gradually but very slowly
interference
new information replaces old: retroactive interference
old may interfere with new: proactive inhibition
so may not forget at all memory is selective …
… affected by emotion – can subconsciously `choose' to
forget
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recall
information reproduced from memory can be assisted
by cues, e.g. categories, imagery
recognition
information gives knowledge that it has been seen
before
less complex than recall - information is cue
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Reasoning
deduction, induction,
abduction
Problem solving
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Deduction:
derive logically necessary conclusion from given premises.
e.g. If it is Friday then she will go to work
It is Friday
Therefore she will go to work.
Logical conclusion not necessarily true:
e.g. If it is raining then the ground is wet
It is raining
Therefore the ground is wet
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When truth and logical validity clash …
e.g. Some people are babies
Some babies cry
Inference - Some people cry
Correct?
People bring world knowledge to bear
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Induction:
generalize from cases seen to cases unseen
e.g. all elephants we have seen have trunks
therefore all elephants have trunks.
Unreliable:
can only prove false not true
… but useful!
Humans not good at using negative evidence
e.g. Wason's cards.
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Is this true?
How many cards do you need to turn over to find
out?
…. and which cards?
If a card has a vowel on one side it has an even number on the other
7 E 4 K
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reasoning from event to cause
e.g. Sam drives fast when drunk.
If I see Sam driving fast, assume drunk.
Unreliable:
can lead to false explanations
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Process of finding solution to unfamiliar task
using knowledge.
Several theories.
Gestalt
problem solving both productive and reproductive
productive draws on insight and restructuring of problem
attractive but not enough evidence to explain `insight' etc.
move away from behaviourism and led towards information
processing theories
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Problem space theory
problem space comprises problem states
problem solving involves generating states using legal
operators
heuristics may be employed to select operators
e.g. means-ends analysis
operates within human information processing system
e.g. STM limits etc.
largely applied to problem solving in well-defined areas
e.g. puzzles rather than knowledge intensive areas
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Analogy
analogical mapping:
novel problems in new domain?
use knowledge of similar problem from similar domain
analogical mapping difficult if domains are semantically different
Skill acquisition
skilled activity characterized by chunking
lot of information is chunked to optimize STM
conceptual rather than superficial grouping of problems
information is structured more effectively
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Types of error
slips
right intention, but failed to do it right
causes: poor physical skill, inattention etc.
change to aspect of skilled behaviour can cause slip
mistakes
wrong intention
cause: incorrect understanding
humans create mental models to explain behaviour.
if wrong (different from actual system) errors can occur
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Various theories of how emotion works
James-Lange: emotion is our interpretation of a
physiological response to a stimuli
Cannon: emotion is a psychological response to
a stimuli
Schacter-Singer: emotion is the result of our
evaluation of our physiological responses, in
the light of the whole situation we are in
Emotion clearly involves both cognitive and physical
responses to stimuli
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The biological response to physical stimuli
is called affect
Affect influences how we respond to
situations
positive creative problem solving
negative narrow thinking
“Negative affect can make it harder to do
even easy tasks; positive affect can make it
easier to do difficult tasks”
(Donald Norman)
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Implications for interface design
stress will increase the difficulty of problem
solving
relaxed users will be more forgiving of
shortcomings in design
aesthetically pleasing and rewarding interfaces
will increase positive affect
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long term
– Gender, physical and intellectual
abilities
short term
– effect of stress or fatigue
changing
– age
Ask yourself:
will design decision exclude section of user
population?
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Some direct applications
e.g. blue acuity is poor
blue should not be used for important detail
However, correct application generally requires
understanding of context in psychology, and an
understanding of particular experimental conditions
A lot of knowledge has been distilled in
guidelines (chap 7)
cognitive models (chap 12)
experimental and analytic evaluation techniques (chap 9)
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a computer system is made up of various elements
each of these elements affects the interaction
input devices – text entry and pointing
output devices – screen (small&large), digital paper
virtual reality – special interaction and display devices
physical interaction – e.g. sound, haptic, bio-sensing
paper – as output (print) and input (scan)
memory – RAM & permanent media, capacity & access
processing – speed of processing, networks
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to understand human–computer interaction
… need to understand computers!
what goes in and out
devices, paper,
sensors, etc.
what can it do?
memory, processing,
networks
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screen, or monitor, on which there are windows
keyboard
mouse/trackpad
variations
desktop
laptop
PDA
the devices dictate the styles of interaction that the system
supports
If we use different devices, then the interface will support a
different style of interaction
window 1
window 2
12-37pm
?
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computers in your house?
hands up, …
… none, 1, 2 , 3, more!!
computers in your pockets?
are you thinking …
… PC, laptop, PDA ??
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in your house?
PC
TV, VCR, DVD, HiFi,
cable/satellite TV
microwave, cooker,
washing machine
central heating
security system
can you think of more?
in your pockets?
PDA
phone, camera
smart card, card
with magnetic strip?
electronic car key
USB memory
try your pockets and
bags
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Long ago in a galaxy far away … batch processing
punched card stacks or large data files prepared
long wait ….
line printer output
… and if it is not right …
Now most computing is interactive
rapid feedback
the user in control (most of the time)
doing rather than thinking …
Is faster always better?
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keyboards (QWERTY et al.)
chord keyboards, phone pads
handwriting, speech
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Most common text input device
Allows rapid entry of text by experienced
users
Keypress closes connection, causing a
character code to be sent
Usually connected by cable, but can be
wireless
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Standardised layout
but …
non-alphanumeric keys are placed differently
accented symbols needed for different scripts
minor differences between UK and USA keyboards
QWERTY arrangement not optimal for typing
– layout to prevent typewriters jamming!
Alternative designs allow faster typing but large social
base of QWERTY typists produces reluctance to
change.
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2 3 4 5 6 7 8 9 0
Q W E R T Y U I
1
O P
S D F H J L
A G K
Z X C V B N M , .
SPACE
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Alphabetic
keys arranged in alphabetic order
not faster for trained typists
not faster for beginners either!
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Dvorak
common letters under dominant fingers
biased towards right hand
common combinations of letters alternate between hands
10-15% improvement in speed and reduction in fatigue
But - large social base of QWERTY typists produce market
pressures not to change
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designs to reduce fatigue for RSI
(Repetitive Strain Injury)
for one handed use
e.g. the Maltron left-handed keyboard
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only a few keys - four or 5
letters typed as combination of keypresses
compact size
– ideal for portable applications
short learning time
– keypresses reflect letter shape
fast
– once you have trained
BUT - social resistance, plus fatigue after
extended use
NEW –market for some wearables
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use numeric keys with
multiple presses
2 – a b c 6 - m n o
3 - d e f 7 - p q r s
4 - g h i 8 - t u v
5 - j k l 9 - w x y z
hello = 4433555[pause]555666
surprisingly fast!
T9 predictive entry
type as if single key for each letter
use dictionary to ‘guess’ the right word
hello = 43556 …
but 26 -> menu ‘am’ or ‘an’
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Text can be input into the computer, using a
pen and a digitizing tablet
natural interaction
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Technical problems:
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
Used in PDAs, and tablet computers …
… leave the keyboard on the desk!
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Improving rapidly
Most successful when:
single user – initial training and learns peculiarities
limited vocabulary systems
Problems with
external noise interfering
imprecision of pronunciation
large vocabularies
different speakers
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for entering numbers quickly:
calculator, PC keyboard
for telephones
not the same!!
ATM like phone
4 5 6
7 8 9
* 0 #
1 2 3
4 5 6
1 2 3
0 . =
7 8 9
telephone calculator
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mouse, touchpad
trackballs, joysticks etc.
touch screens, tablets
eyegaze, cursors
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Handheld pointing device
very common
easy to use
Two characteristics
planar movement
buttons
(usually from 1 to 3 buttons on top, used for making a
selection, indicating an option, or to initiate drawing
etc.)
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Mouse located on desktop
requires physical space
no arm fatigue
Relative movement only is detectable.
Movement of mouse moves screen cursor
Screen cursor oriented in (x, y) plane,
mouse movement in (x, z) plane …
… an indirect manipulation device.
device itself doesn’t obscure screen, is accurate and fast.
hand-eye coordination problems for novice users
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Two methods for detecting motion
Mechanical
Ball on underside of mouse turns as mouse is moved
Rotates orthogonal potentiometers
Can be used on almost any flat surface
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Two methods for detecting motion
Optical
light emitting diode on underside of mouse
may use special grid-like pad or just on desk
less susceptible to dust and dirt
detects fluctuating alterations in reflected light intensity to
calculate relative motion in (x, z) plane
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some experiments with the footmouse
controlling mouse movement with feet …
not very common :-)
but foot controls are common elsewhere:
car pedals
sewing machine speed control
organ and piano pedals
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small touch sensitive tablets
‘stroke’ to move mouse pointer
used mainly in laptop computers
good ‘acceleration’ settings important
fast stroke
lots of pixels per inch moved
initial movement to the target
slow stroke
less pixels per inch
for accurate positioning
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Trackball
ball is rotated inside static housing
like an upside down mouse!
relative motion moves cursor
indirect device, fairly accurate
separate buttons for picking
very fast for gaming
used in some portable and notebook computers.
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Thumbwheels …
for accurate CAD – two dials for X-Y cursor position
for fast scrolling – single dial on mouse
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Joystick
indirect
pressure of stick = velocity of movement
buttons for selection
on top or on front like a trigger
often used for computer games
aircraft controls and 3D navigation
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Keyboard nipple
for laptop computers
miniature joystick in the middle of the keyboard
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Detect the presence of finger or stylus on the screen.
works by interrupting matrix of light beams, capacitance changes or
ultrasonic reflections
direct pointing device
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Advantages:
fast, and requires no specialised pointer
good for menu selection
suitable for use in hostile environment: clean and safe from damage.
Disadvantages:
finger can mark screen
imprecise (finger is a fairly blunt instrument!)
difficult to select small regions or perform accurate drawing
lifting arm can be tiring
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Stylus
small pen-like pointer to draw directly on screen
may use touch sensitive surface or magnetic detection
used in PDA, tablets PCs and drawing tables
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Light Pen
now rarely used
uses light from screen to detect location
BOTH …
very direct and obvious to use
but can obscure screen
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Mouse like-device with cross hairs
used on special surface
- rather like stylus
very accurate
- used for digitizing maps
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control interface by eye gaze direction
e.g. look at a menu item to select it
uses laser beam reflected off retina
… a very low power laser!
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mainly used for evaluation
potential for hands-free control
high accuracy requires headset
cheaper and lower accuracy devices available
sit under the screen like a small webcam
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Four keys (up, down, left, right) on keyboard.
Very, very cheap, but slow.
Useful for not much more than basic motion for text-
editing tasks.
No standardised layout, but inverted “T”, most
common
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in phones, TV controls etc.
cursor pads or mini-joysticks
discrete left-right, up-down
mainly for menu selection
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bitmap screens (CRT & LCD)
large & situated displays
digital paper
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Resolution … used (inconsistently) for
number of pixels on screen (width x height)
e.g. SVGA 1024 x 768, PDA perhaps 240x400
density of pixels (in pixels or dots per inch - dpi)
typically between 72 and 96 dpi
Aspect ratio
ration between width and height
4:3 for most screens, 16:9 for wide-screen TV
Colour depth:
how many different colours for each pixel?
black/white or greys only
256 from a pallete
8 bits each for red/green/blue = millions of colours
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Jaggies
diagonal lines that have discontinuities in due to horizontal
raster scan process.
Anti-aliasing
softens edges by using shades of line colour
also used for text
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Stream of electrons emitted from electron gun,
focused and directed by magnetic fields, hit phosphor-
coated screen which glows
used in TVs and computer monitors
electron gun
focussing and
deflection
electron beam
phosphor-
coated screen
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X-rays: largely absorbed by screen (but not at rear!)
UV- and IR-radiation from phosphors: insignificant
levels
Radio frequency emissions, plus ultrasound (~16kHz)
Electrostatic field - leaks out through tube to user.
Intensity dependant on distance and humidity. Can
cause rashes.
Electromagnetic fields (50Hz-0.5MHz). Create
induction currents in conductive materials, including
the human body. Two types of effects attributed to
this: visual system - high incidence of cataracts in
VDU operators, and concern over reproductive
disorders (miscarriages and birth defects).
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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
bright window
work in well-lit surroundings
Take extra care if pregnant.
but also posture, ergonomics, stress
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Smaller, lighter, and … no radiation problems.
Found on PDAs, portables and notebooks,
… and increasingly on desktop and even for home TV
also used in dedicated displays:
digital watches, mobile phones, HiFi controls
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How it works …
Top plate transparent and polarised, bottom plate
reflecting.
Light passes through top plate and crystal, and reflects
back to eye.
Voltage applied to crystal changes polarisation and
hence colour
N.B. light reflected not emitted => less eye strain
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Random Scan (Directed-beam refresh, vector display)
draw the lines to be displayed directly
no jaggies
lines need to be constantly redrawn
rarely used except in special instruments
Direct view storage tube (DVST)
Similar to random scan but persistent => no flicker
Can be incrementally updated but not selectively erased
Used in analogue storage oscilloscopes
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used for meetings, lectures, etc.
technology
plasma – usually wide screen
video walls – lots of small screens together
projected – RGB lights or LCD projector
– hand/body obscures screen
– may be solved by 2 projectors +
– clever software
back-projected
– frosted glass + projector behind
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displays in ‘public’ places
large or small
very public or for small group
display only
for information relevant to location
or interactive
use stylus, touch sensitive screen
in all cases … the location matters
meaning of information or interaction is related to the
location
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small displays beside office doors
handwritten notes left using stylus
office owner reads notes using web interface
small displays
beside
office doors
handwritten
notes left
using stylus
office owner
reads notes
using web interface
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positioning in 3D space
moving and grasping
seeing 3D (helmets and caves)
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cockpit and virtual controls
steering wheels, knobs and dials … just like real!
111. 4/6/2022 SRM University Ramapuram 111
the 3D mouse
six-degrees of movement: x, y, z + roll, pitch, yaw
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data glove
fibre optics used to detect finger position
114. 4/6/2022 SRM University Ramapuram 114
VR helmets
detect head motion and possibly eye gaze
115. 4/6/2022 SRM University Ramapuram 115
whole body tracking
accelerometers strapped to limbs or reflective dots
and video processing
116. 4/6/2022 SRM University Ramapuram 116
desktop VR
ordinary screen, mouse or keyboard control
perspective and motion give 3D effect
seeing in 3D
use stereoscopic vision
VR helmets
screen plus shuttered specs, etc.
117. 4/6/2022 SRM University Ramapuram 117
small TV screen for each eye
slightly different angles
3D effect
118. 4/6/2022 SRM University Ramapuram 118
time delay
move head … lag … display moves
conflict: head movement vs. eyes
depth perception
headset gives different stereo distance
but all focused in same plane
conflict: eye angle vs. focus
conflicting cues => sickness
helps motivate improvements in technology
119. 4/6/2022 SRM University Ramapuram 119
scenes projected on walls
realistic environment
hydraulic rams!
real controls
other people
120. 4/6/2022 SRM University Ramapuram 120
special displays and gauges
sound, touch, feel, smell
physical controls
environmental and bio-sensing
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analogue representations:
dials, gauges, lights, etc.
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digital displays:
small LCD screens, LED lights, etc.
123. 4/6/2022 SRM University Ramapuram 123
head-up displays
found in aircraft cockpits
show most important controls
… depending on context
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beeps, bongs, clonks, whistles and whirrs
used for error indications
confirmation of actions e.g. keyclick
125. 4/6/2022 SRM University Ramapuram 125
touch and feeling important
in games … vibration, force feedback
in simulation … feel of surgical instruments
called haptic devices
texture, smell, taste
current technology very limited
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for controlling menus
feel small ‘bumps’ for each item
makes it easier to select options by feel
uses haptic technology from Immersion Corp.
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specialist controls needed …
industrial controls, consumer products, etc.
large buttons
clear dials
tiny buttons
multi-function
control
easy-clean
smooth buttons
128. 4/6/2022 SRM University Ramapuram 128
sensors all around us
car courtesy light – small switch on door
ultrasound detectors – security, washbasins
RFID security tags in shops
temperature, weight, location
… and even our own bodies …
iris scanners, body temperature, heart rate,
galvanic skin response, blink rate
130. 4/6/2022 SRM University Ramapuram 130
image made from small dots
allows any character set or graphic to be
printed,
critical features:
resolution
size and spacing of the dots
measured in dots per inch (dpi)
speed
usually measured in pages per minute
cost!!
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dot-matrix printers
use inked ribbon (like a typewriter
line of pins that can strike the ribbon, dotting the paper.
typical resolution 80-120 dpi
132. 4/6/2022 SRM University Ramapuram 132
ink-jet and bubble-jet printers
tiny blobs of ink sent from print head to paper
typically 300 dpi or better .
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laser printer
like photocopier: dots of electrostatic charge deposited on drum,
which picks up toner (black powder form of ink) rolled onto paper
which is then fixed with heat
typically 600 dpi or better.
134. 4/6/2022 SRM University Ramapuram 134
shop tills
dot matrix
same print head used for several paper rolls
may also print cheques
135. 4/6/2022 SRM University Ramapuram 135
thermal printers
special heat-sensitive paper
paper heated by pins makes a dot
poor quality, but simple & low maintenance
used in some fax machines
136. 4/6/2022 SRM University Ramapuram 136
Font – the particular style of text
Courier font
Helvetica font
Palatino font
Times Roman font
§´ (special symbol)
Size of a font measured in points (1 pt about 1/72”)
(vaguely) related to its height
This is ten point Helvetica
This is twelve point
This is fourteen point
This is eighteen point
and this is twenty-four point
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Pitch
fixed-pitch – every character has the same width
e.g. Courier
variable-pitched – some characters wider
e.g. Times Roman – compare the ‘i’ and the “m”
Serif or Sans-serif
sans-serif – square-ended strokes
e.g. Helvetica
serif – with splayed ends (such as)
e.g. Times Roman or Palatino
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lowercase
easy to read shape of words
UPPERCASE
better for individual letters and non-words
e.g. flight numbers: BA793 vs. ba793
serif fonts
helps your eye on long lines of printed text
but sans serif often better on screen
139. 4/6/2022 SRM University Ramapuram 139
Pages very complex
different fonts, bitmaps, lines, digitised photos, etc.
Can convert it all into a bitmap and send to the
printer
… but often huge !
Alternatively Use a page description language
sends a description of the page can be sent,
instructions for curves, lines, text in different styles, etc.
like a programming language for printing!
PostScript is the most common
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WYSIWYG
what you see is what you get
aim of word processing, etc.
but …
screen: 72 dpi, landscape image
print: 600+ dpi, portrait
can try to make them similar
but never quite the same
so … need different designs, graphics etc, for
screen and print
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Take paper and convert it into a bitmap
Shines light at paper and note intensity of reflection
colour or greyscale
Typical resolutions from 600–2400 dpi
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Two sorts of scanner
flat-bed: paper placed on a glass plate, whole page converted into
bitmap
hand-held: scanner passed over paper, digitising strip typically 3-
4” wide
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Used in
desktop publishing for incorporating
photographs and other images
document storage and retrieval systems,
doing away with paper storage
+ special scanners for slides and photographic
negatives
144. 4/6/2022 SRM University Ramapuram 144
OCR converts bitmap back into text
different fonts
create problems for simple
“template matching”
algorithms
more complex systems segment text,
decompose it into lines and arcs, and decipher
characters that way
page format
columns, pictures, headers and footers
145. 4/6/2022 SRM University Ramapuram 145
paper usually regarded as output
only
can be input too – OCR, scanning,
etc.
Xerox PaperWorks
glyphs – small patterns of ///
used to identify forms etc.
used with scanner and fax to control applications
more recently
papers micro printed - like wattermarks
identify which sheet and where you are
special ‘pen’ can read locations
know where they are writing
146. 4/6/2022 SRM University Ramapuram 146
short term and long term
speed, capacity, compression
formats, access
147. 4/6/2022 SRM University Ramapuram 147
Random access memory (RAM)
on silicon chips
100 nano-second access time
usually volatile (lose information if power turned off)
data transferred at around 100 Mbytes/sec
Some non-volatile RAM used to store basic set-up
information
Typical desktop computers:
64 to 256 Mbytes RAM
148. 4/6/2022 SRM University Ramapuram 148
magnetic disks
floppy disks store around 1.4 Mbytes
hard disks typically 40 Gbytes to 100s of Gbytes
access time ~10ms, transfer rate 100kbytes/s
149. 4/6/2022 SRM University Ramapuram 149
optical disks
use lasers to read and sometimes write
more robust that magnetic media
CD-ROM
- same technology as home audio, ~ 600 Gbytes
DVD - for AV applications, or very large files
150. 4/6/2022 SRM University Ramapuram 150
PDAs
often use RAM for their main memory
Flash-Memory
used in PDAs, cameras etc.
silicon based but persistent
plug-in USB devices for data transfer
151. 4/6/2022 SRM University Ramapuram 151
what do the numbers mean?
some sizes (all uncompressed) …
this book, text only ~ 320,000 words, 2Mb
the Bible ~ 4.5 Mbytes
scanned page ~ 128 Mbytes
(11x8 inches, 1200 dpi, 8bit greyscale)
digital photo ~ 10 Mbytes
(2–4 mega pixels, 24 bit colour)
video ~ 10 Mbytes per second
(512x512, 12 bit colour, 25 frames per sec)
152. 4/6/2022 SRM University Ramapuram 152
Problem:
running lots of programs + each program large
not enough RAM
Solution - Virtual memory :
store some programs temporarily on disk
makes RAM appear bigger
But … swapping
program on disk needs to run again
copied from disk to RAM
s l o w s t h i n g s d o w n
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reduce amount of storage required
lossless
recover exact text or image – e.g. GIF, ZIP
look for commonalities:
text: AAAAAAAAAABBBBBCCCCCCCC 10A5B8C
video: compare successive frames and store change
154. 4/6/2022 SRM University Ramapuram 154
lossy
recover something like original – e.g. JPEG, MP3
exploit perception
JPEG: lose rapid changes and some colour
MP3: reduce accuracy of drowned out notes
155. 4/6/2022 SRM University Ramapuram 155
ASCII - 7-bit binary code for to each letter and
character
156. 4/6/2022 SRM University Ramapuram 156
RTF (rich text format)
- text plus formatting and layout information
157. 4/6/2022 SRM University Ramapuram 157
ASCII - 7-bit binary code for to each letter and
character
UTF-8 - 8-bit encoding of 16 bit character set
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SGML (standardized generalised markup language)
- documents regarded as structured objects
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XML (extended markup language)
- simpler version of SGML for web applications
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Images:
many storage formats :
(PostScript, GIFF, JPEG, TIFF, PICT, etc.)
plus different compression techniques
(to reduce their storage requirements)
Audio/Video
again lots of formats :
(QuickTime, MPEG, WAV, etc.)
compression even more important
also ‘streaming’ formats for network delivery
161. 4/6/2022 SRM University Ramapuram 161
large information store
long time to search => use index
what you index -> what you can access
simple index needs exact match
forgiving systems:
Xerox “do what I mean” (DWIM)
SOUNDEX – McCloud ~ MacCleod
access without structure …
free text indexing (all the words in a document)
needs lots of space!!
162. 4/6/2022 SRM University Ramapuram 162
finite speed (but also Moore’s law)
limits of interaction
networked computing
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Designers tend to assume fast processors, and make
interfaces more and more complicated
But problems occur, because processing cannot keep
up with all the tasks it needs to do
cursor overshooting because system has buffered keypresses
icon wars - user clicks on icon, nothing happens, clicks on another,
then system responds and windows fly everywhere
Also problems if system is too fast - e.g. help screens
may scroll through text much too rapidly to be read
164. 4/6/2022 SRM University Ramapuram 164
computers get faster and faster!
1965 …
Gordon Moore, co-founder of Intel, noticed a
pattern
processor speed doubles every 18 months
PC … 1987: 1.5 Mhz, 2002: 1.5 GHz
similar pattern for memory
but doubles every 12 months!!
hard disk … 1991: 20Mbyte : 2002: 30 Gbyte
baby born today
record all sound and vision
by 70 all life’s memories stored in a grain of dust!
165. 4/6/2022 SRM University Ramapuram 165
implicit assumption … no delays
an infinitely fast machine
what is good design for real machines?
good example … the telephone :
type keys too fast
hear tones as numbers sent down the line
actually an accident of implementation
emulate in deisgn
166. 4/6/2022 SRM University Ramapuram 166
Computation bound
Computation takes ages, causing frustration for the user
Storage channel bound
Bottleneck in transference of data from disk to memory
Graphics bound
Common bottleneck: updating displays requires a lot of effort -
sometimes helped by adding a graphics co-processor optimised to
take on the burden
Network capacity
Many computers networked - shared resources and files, access to
printers etc. - but interactive performance can be reduced by
slow network speed
167. 4/6/2022 SRM University Ramapuram 167
Networks allow access to …
large memory and processing
other people (groupware, email)
shared resources – esp. the web
Issues
network delays – slow feedback
conflicts - many people update data
unpredictability
168. 4/6/2022 SRM University Ramapuram 168
history …
1969: DARPANET US DoD, 4 sites
1971: 23; 1984: 1000; 1989: 10000
common language (protocols):
TCP – Transmission Control protocol
lower level, packets (like letters) between machines
IP – Internet Protocol
reliable channel (like phone call) between programs on
machines
email, HTTP, all build on top of these
169. 4/6/2022 SRM University Ramapuram 169
interaction models
translations between user and system
ergonomics
physical characteristics of interaction
interaction styles
the nature of user/system dialog
context
social, organizational, motivational
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communication
user system
but is that all … ?
see “language and action” in chapter 4 …
171. 4/6/2022 SRM University Ramapuram 171
terms of interaction
Norman model
interaction framework
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domain – the area of work under study
e.g. graphic design
goal – what you want to achieve
e.g. create a solid red triangle
task – how you go about doing it
– ultimately in terms of operations or actions
e.g. … select fill tool, click over triangle
Note …
traditional interaction …
use of terms differs a lot especially task/goal !!!
173. 4/6/2022 SRM University Ramapuram 173
Seven stages
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
Norman’s model concentrates on user’s view
of the interface
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user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
system
evaluation
execution
goal
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user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
system
evaluation
execution
goal
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user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
system
evaluation
execution
goal
177. 4/6/2022 SRM University Ramapuram 177
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
system
evaluation
execution
goal
178. 4/6/2022 SRM University Ramapuram 178
Some systems are harder to use than others
Gulf of Execution
user’s formulation of actions
≠ actions allowed by the system
Gulf of Evaluation
user’s expectation of changed system state
≠ actual presentation of this state
179. 4/6/2022 SRM University Ramapuram 179
slip
understand system and goal
correct formulation of action
incorrect action
mistake
may not even have right goal!
Fixing things?
slip – better interface design
mistake – better understanding of system
180. 4/6/2022 SRM University Ramapuram 180
extension of Norman…
their interaction framework has 4 parts
user
input
system
output
each has its own unique language
interaction translation between languages
problems in interaction = problems in translation
S
core
U
task
O
output
I
input
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user intentions
translated into actions at the interface
translated into alterations of system state
reflected in the output display
interpreted by the user
general framework for understanding
interaction
not restricted to electronic computer systems
identifies all major components involved in interaction
allows comparative assessment of systems
an abstraction
183. 4/6/2022 SRM University Ramapuram 183
Study of the physical characteristics of
interaction
Also known as human factors – but this can
also be used to mean much of HCI!
Ergonomics good at defining standards and
guidelines for constraining the way we design
certain aspects of systems
184. 4/6/2022 SRM University Ramapuram 184
arrangement of controls and displays
e.g. controls grouped according to function or
frequency of use, or sequentially
surrounding environment
e.g. seating arrangements adaptable to cope with all
sizes of user
health issues
e.g. physical position, environmental conditions
(temperature, humidity), lighting, noise,
use of colour
e.g. use of red for warning, green for okay,
awareness of colour-blindness etc.
185. 4/6/2022 SRM University Ramapuram 185
Office interface vs. industrial interface?
Context matters!
office industrial
type of data textual numeric
rate of change slow fast
environment clean dirty
… the oil soaked mouse!
186. 4/6/2022 SRM University Ramapuram 186
industrial interface:
traditional … dials and knobs
now … screens and keypads
glass interface
+ cheaper, more flexible,
multiple representations,
precise values
not physically located,
loss of context,
complex interfaces
may need both
Vessel B Temp
0 100 200
113
multiple representations
of same information
187. 4/6/2022 SRM University Ramapuram 187
office– direct manipulation
user interacts
with artificial world
industrial – indirect manipulation
user interacts
with real world
through interface
issues ..
feedback
delays
system
interface plant
immediate
feedback
instruments
188. 4/6/2022 SRM University Ramapuram 188
dialogue … computer and
user
distinct styles of interaction
189. 4/6/2022 SRM University Ramapuram 189
command line interface
menus
natural language
question/answer and query dialogue
form-fills and spreadsheets
WIMP
point and click
three–dimensional interfaces
190. 4/6/2022 SRM University Ramapuram 190
Way of expressing instructions to the
computer directly
function keys, single characters, short abbreviations,
whole words, or a combination
suitable for repetitive tasks
better for expert users than novices
offers direct access to system functionality
command names/abbreviations should be
meaningful!
Typical example: the Unix system
191. 4/6/2022 SRM University Ramapuram 191
Set of options displayed on the screen
Options visible
less recall - easier to use
rely on recognition so names should be meaningful
Selection by:
numbers, letters, arrow keys, mouse
combination (e.g. mouse plus accelerators)
Often options hierarchically grouped
sensible grouping is needed
Restricted form of full WIMP system
192. 4/6/2022 SRM University Ramapuram 192
Familiar to user
speech recognition or typed natural language
Problems
vague
ambiguous
hard to do well!
Solutions
try to understand a subset
pick on key words
193. 4/6/2022 SRM University Ramapuram 193
Question/answer interfaces
user led through interaction via series of questions
suitable for novice users but restricted functionality
often used in information systems
Query languages (e.g. SQL)
used to retrieve information from database
requires understanding of database structure and
language syntax, hence requires some expertise
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Primarily for data entry or data retrieval
Screen like paper form.
Data put in relevant place
Requires
good design
obvious correction
facilities
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first spreadsheet VISICALC, followed by
Lotus 1-2-3
MS Excel most common today
sophisticated variation of form-filling.
grid of cells contain a value or a formula
formula can involve values of other cells
e.g. sum of all cells in this column
user can enter and alter data spreadsheet
maintains consistency
196. 4/6/2022 SRM University Ramapuram 196
Windows
Icons
Menus
Pointers
… or windows, icons, mice, and pull-down menus!
default style for majority of interactive
computer systems, especially PCs and
desktop machines
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used in ..
multimedia
web browsers
hypertext
just click something!
icons, text links or location on map
minimal typing
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virtual reality
‘ordinary’ window systems
highlighting
visual affordance
indiscriminate use
just confusing!
3D workspaces
use for extra virtual space
light and occlusion give depth
distance effects
flat buttons …
… or sculptured
click me!
200. 4/6/2022 SRM University Ramapuram 200
Areas of the screen that behave as if they
were independent
can contain text or graphics
can be moved or resized
can overlap and obscure each other, or can be laid
out next to one another (tiled)
scrollbars
allow the user to move the contents of the window up
and down or from side to side
title bars
describe the name of the window
201. 4/6/2022 SRM University Ramapuram 201
small picture or image
represents some object in the interface
often a window or action
windows can be closed down (iconised)
small representation fi many accessible
windows
icons can be many and various
highly stylized
realistic representations.
202. 4/6/2022 SRM University Ramapuram 202
important component
WIMP style relies on pointing and selecting things
uses mouse, trackpad, joystick, trackball,
cursor keys or keyboard shortcuts
wide variety of graphical images
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Choice of operations or services offered on the
screen
Required option selected with pointer
problem – take a lot of screen space
solution – pop-up: menu appears when needed
File Edit Options
Typewriter
Screen
Times
Font
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Menu Bar at top of screen (normally), menu
drags down
pull-down menu - mouse hold and drag down menu
drop-down menu - mouse click reveals menu
fall-down menus - mouse just moves over bar!
Contextual menu appears where you are
pop-up menus - actions for selected object
pie menus - arranged in a circle
easier to select item (larger target area)
quicker (same distance to any option)
… but not widely used!
205. 4/6/2022 SRM University Ramapuram 205
Cascading menus
hierarchical menu structure
menu selection opens new menu
and so in ad infinitum
Keyboard accelerators
key combinations - same effect as menu item
two kinds
active when menu open – usually first letter
active when menu closed – usually Ctrl + letter
usually different !!!
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which kind to use
what to include in menus at all
words to use (action or description)
how to group items
choice of keyboard accelerators
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individual and isolated regions within a
display that can be selected to invoke an
action
Special kinds
radio buttons
– set of mutually exclusive choices
check boxes
– set of non-exclusive choices
208. 4/6/2022 SRM University Ramapuram 208
long lines of icons …
… but what do they do?
fast access to common actions
often customizable:
choose which toolbars to see
choose what options are on it
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Problem
menu not there when you want it
Solution
palettes – little windows of actions
shown/hidden via menu option
e.g. available shapes in drawing package
tear-off and pin-up menus
menu ‘tears off’ to become palette
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information windows that pop up to inform
of an important event or request
information.
e.g: when saving a file, a dialogue box is
displayed to allow the user to specify the
filename and location. Once the file is saved,
the box disappears.
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rapidly improving …
… but still inaccurate
how to have robust dialogue?
… interaction of course!
e.g. airline reservation:
reliable “yes” and “no”
+ system reflects back its understanding
“you want a ticket from New York to Boston?”
213. 4/6/2022 SRM University Ramapuram 213
WIMP systems have the same elements:
windows, icons, menus, pointers, buttons, etc.
but different window systems
… behave differently
e.g. MacOS vs Windows menus
appearance + behaviour = look and feel
214. 4/6/2022 SRM University Ramapuram 214
who has the initiative?
old question–answer– computer
WIMP interface – user
WIMP exceptions …
pre-emptive parts of the interface
modal dialog boxes
come and won’t go away!
good for errors, essential steps
but use with care
215. 4/6/2022 SRM University Ramapuram 215
can’t always avoid errors …
… but we can put them right
make it easy to detect errors
… then the user can repair them
hello, this is the Go Faster booking system
what would you like?
(user) I want to fly from New York to London
you want a ticket from New York to Boston
(user) no
sorry, please confirm one at a time
do you want to fly from New York
(user) yes
… … …
216. 4/6/2022 SRM University Ramapuram 216
Interaction affected by social and organizational
context
other people
desire to impress, competition, fear of failure
motivation
fear, allegiance, ambition, self-satisfaction
inadequate systems
cause frustration and lack of motivation
217. 4/6/2022 SRM University Ramapuram 217
designing experience
physical engagement
managing value
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home, entertainment, shopping
not enough that people can use a system
they must want to use it!
psychology of experience
flow (Csikszentimihalyi)
balance between anxiety and boredom
education
zone of proximal development
things you can just do with help
wider ...
literary analysis, film studies, drama
219. 4/6/2022 SRM University Ramapuram 219
real crackers
cheap and cheerful!
bad joke, plastic toy, paper hat
pull and bang
220. 4/6/2022 SRM University Ramapuram 220
virtual crackers
cheap and cheerful
bad joke, web toy, cut-out mask
click and bang
221. 4/6/2022 SRM University Ramapuram 221
virtual crackers
cheap and cheerful
bad joke, web toy, cut-out mask
click and bang
222. 4/6/2022 SRM University Ramapuram 222
sender
fill in web form
To: wxv
From: ..
receive email recipient
closed
cracker page
open
message
recipient clicks
cracker opens ...
very slowly
joke
links
open
cracker page
web toy
mask
sender
watches
progress
223. 4/6/2022 SRM University Ramapuram 223
real cracker virtual cracker
Surface elements
design cheap and cheerful simple page/graphics
play plastic toy and joke web toy and joke
dressing up paper hat mask to cut out
Experienced effects
shared offered to another sent by email message
co-experience pulled together sender can't see content
until opened by recipient
excitement cultural connotations recruited expectation
hiddenness contents inside first page - no contents
suspense pulling cracker slow ... page change
surprise bang (when it works) WAV file (when it works)
224. 4/6/2022 SRM University Ramapuram 224
many constraints:
ergonomic – minimum button size
physical – high-voltage switches are big
legal and safety – high cooker controls
context and environment – easy to clean
aesthetic – must look good
economic – … and not cost too much!
225. 4/6/2022 SRM University Ramapuram 225
constraints are contradictory … need trade-offs
within categories:
e.g. safety – cooker controls
front panel – safer for adult
rear panel – safer for child
between categories
e.g. ergonomics vs. physical – MiniDisc remote
ergonomics – controls need to be bigger
physical – no room!
solution – multifunction controls & reduced functionality
226. 4/6/2022 SRM University Ramapuram 226
do external physical aspects reflect logical
effect?
related to affordance (chap 5)
logical state revealed in physical state?
e.g. on/off buttons
inverse actions inverse effects?
e.g. arrow buttons, twist controls
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yes/no buttons
well sort of
‘joystick’
also left side control
228. 4/6/2022 SRM University Ramapuram 228
one-shot buttons
joystick
some sliders
good – large selection sets
bad – hidden state
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series of spring-back controls
each cycle through some options
–natural inverse back/forward
twist for track movement
pull and twist for volume
– spring back
– natural inverse for twist
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state evident in
mechanical buttons rotary knobs reveal internal state
and can be controlled by both user
and machine
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people use something
ONLY IF
it has perceived value
AND
value exceeds cost
BUT NOTE
exceptions (e.g. habit)
value NOT necessarily personal gain or money
233. 4/6/2022 SRM University Ramapuram 233
value
helps me get my work done
fun
good for others
cost
download time
money £, $, €
learning effort
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in economics Net Present Value:
discount by (1+rate)years to wait
in life people heavily discount
future value and future cost
hence resistance to learning
need low barriers
and high perceived present value
235. 4/6/2022 SRM University Ramapuram 235
value for people who have the book
helps you to look up things
chapter and page number
value for those who don’t …
sort of online mini-encyclopaedia
full paragraph of context
… but also says “buy me”!!
… but also says “buy me”!!
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coercion
tell people what to do!
value = keep your job
enculturation
explain corporate values
establish support (e.g share options)
emergence
design process so that
individuals value organisational value
237. 4/6/2022 SRM University Ramapuram 237
Alan Dix- Janet Finlay Gregory D.
Abowd- Russel Beale- Human –
Computer Interaction, Pearson
Education- 3 rd Edition- 2004.
John M.Caroll, Human – Computer
Interaction in the Millennium,
Pearson Education- 3rd Edition-
2000.
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School of Computing, Department of IT 237
238. 4/6/2022 SRM University Ramapuram 238
1. State law of size constancy.
2. State Fitts law.
3. What is saccade?
4. List the three types of sensory receptors
in skin.
5. What is recency effect?
6. Mention the two types of long term
memory.
7. What is total time hypothesis?
8. What is distribution of practice effect?
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School of Computing, Department of IT 238
239. 4/6/2022 SRM University Ramapuram 239
9. What is Retroactive interference?
10. What is proactive inhibition?
11. What is deductive reasoning?
12. What is inductive reasoning?
13. Differentiate track ball and mouse.
14. Draw the various cursor key layouts.
15. What is antialiasing?
16. What is the use of virtual reality helmets?
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School of Computing, Department of IT 239
240. 4/6/2022 SRM University Ramapuram 240
17. List the factors that can limit the speed of
an interactive system.
18. Define ergonomics.
19. List the factors in the physical
environment that directly affect the
quality of the interaction and the user’s
performance.
20. What is a palette?
8/22/2011
School of Computing, Department of IT 240