The computer

The Computer
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
Interacting with computers

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
 A ‘typical’ computer system
? • screen, or monitor, on which there are windows
• keyboard
window 1
• mouse/trackpad
window 2
• variations
– desktop
– laptop
– PDA
12-37pm

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
How many …

• computers in your house?

– hands up, …
… none, 1, 2 , 3, more!!

• computers in your pockets?

are you thinking …

… PC, laptop, PDA ??
How many computers …

in your house? in your pockets?

– PC – PDA
– TV, VCR, DVD, HiFi, – phone, camera
cable/satellite TV – smart card, card with
– microwave, cooker, magnetic strip?
washing machine – electronic car key
– central heating – USB memory
– security system
try your pockets and
can you think of more? bags
Interactivity?

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?

What is meant by Batch
processing?
• Batch processing interactions takes
place over hours or days.
• In contrast the typical desktop
computer system has interactions
taking seconds or fractions of a second
(or with slow web pages sometimes
minutes!).
The field of Human Computer
Interaction largely grew due to this
change in interactive pace. It is easy to
assume that faster means better, but
some of the paper-based technology.
Batch Processing (Past
Systems)

• In early computing, users submitted

jobs (e.g., code, data) and waited
hours or days for results.
• There was no real-time interaction
between user and computer.
• Common in mainframe or paper-based
systems.
• Example: Submitting punch cards and
waiting for the output the next day.
 Interactive Systems (Modern
Systems)

• Current desktop and web-based systems allow

interaction in seconds or fractions of a
second.
• Immediate feedback is possible: you click a
button → see a result instantly.
• Even with slow internet, delays are just
minutes, not days.
 Richer Interaction

• Richer interaction in (HCI) refers to more natural,

expressive, and multi-sensory ways for humans to
interact with computers. It moves beyond just
keyboard and mouse to include gesture, voice,
touch, emotion, and context-aware inputs.
What is richer interaction in
HCI?

• Today, rich interaction is software that

is very intuitive and easy to use.
• In the future, rich interaction will be
voice and speech recognition that
actually recognizes anyone's spoken
command and robotic devices that
automatically assist people.
Richer interaction

sensors
and devices
everywhere
 text entry devices

keyboards (QWERTY et al.)

chord keyboards, phone pads
handwriting, speech
Keyboards

• 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
layout – QWERTY

• 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.
QWERTY (ctd)

1 2 3 4 5 6 7 8 9 0
Q W E R T Y U I O P
A S D F G H J K L
Z X C V B N M , .
SPACE
alternative keyboard layouts
Alphabetic
– keys arranged in alphabetic order
– not faster for trained typists
– not faster for beginners either!
alternative keyboard layouts
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
special keyboards

• designs to reduce fatigue for RSI

• for one handed use
e.g. the Maltron left-handed keyboard
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 letter shape
fast
– once you have trained

BUT - social resistance, plus fatigue after extended use

NEW – niche market for some wearables
phone pad and T9 entry
• use numeric keys with
multiple presses
2 –abc 6
mno -
3 -def 7
pqrs-
4 -ghi 8
tuv -
5 -jkl 9
wxyz-
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’
Handwriting recognition

• Text can be input into the computer, using a

pen and a digesting tablet
– natural interaction

• 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!
 Speech recognition
• Speech recognition systems convert spoken
language into text that computers can understand
and process.
• 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
Single User – Initial Training:
• Systems perform best when trained on one
speaker’s voice.
• The system learns that person’s:
– Accent
– Tone
– Speech patterns
• Example: Older software like Dragon
NaturallySpeaking required user-specific training.
• Limited Vocabulary Systems:
– Accuracy is higher when the range of possible
words is small and specific.
– Useful in:
• Voice-controlled systems
• Navigation devices
• Command-based environments
– Less confusion, fewer similar-sounding words.
Problems / Limitations:
Numeric keypads

• for entering numbers quickly:

– calculator, PC keyboard
• for telephones
1 2 3 7 8 9
not the same!! 4 5 6 4 5 6
7 8 9 1 2 3
ATM like phone
0 # 0 . =
*
telephone calculator
positioning, pointing and drawing

mouse, touchpad
trackballs, joysticks etc.
touch screens, tablets
eyegaze, cursors
the Mouse

• 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.)
the mouse (ctd)
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
How does it work?
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

• 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
Even by foot …

• 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
Touchpad

• 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
Trackball and thumbwheels
Trackball
A trackball is a computer cursor control device
used in many laptop computer keyboards and older
versions of computer mice.
– ball is rotated inside static housing
• like an upsdie 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.
• A trackball is an input device used to control
the movement of a cursor on a screen. It is
similar to a mouse but works differently in its
operation
• A ball is embedded in a static housing
(it doesn’t move like a mouse).
• The user rotates the ball with fingers,
thumb, or palm.
• The rotation of the ball translates into
relative cursor movement on the
screen
Trackball and thumbwheels
Thumbwheels …
a spinning wheel usually spun by a thumb and
generally located on a keyboard or mouse or
on handheld devices (such as handheld
radios).
– for accurate CAD – two dials for X-Y cursor position
– for
– fast scrolling – single dial on mouse
 Joystick and keyboard nipple
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

Keyboard nipple
– for laptop computers
– miniature joystick in the middle
– of the keyboard
Touch-sensitive screen
• 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

• 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
Stylus and light pen

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

Light Pen
– now rarely used
– uses light from screen to detect location

BOTH …
– very direct and obvious to use
– but can obscure screen
Digitizing tablet

• Mouse like-device with cross hairs

• used on special surface

- rather like stylus

• very accurate
- used for digitizing maps
 Eye Gaze
• An eye gaze control interface allows a user to control a
computer or system simply by looking at it — using eye
movements instead of hands or traditional input devices like
a mouse or keyboard.

How It Works:
• The system tracks where the user is looking on the screen.
• To make a selection (e.g., a menu item), the user looks
directly at it.
• A very low-power laser beam (safe for the eyes) is
reflected off the retina.
• The reflected signal is detected and interpreted to identify
gaze direction.
 Examples

Gaming with Eye Tracking

• Use Case:
In games like "Assassin’s Creed" or "The Division 2"
(with Tobii Eye Tracker support), players can:
• Aim or look at enemies using their eyes.
• Trigger context-based actions by just looking at a
spot on the screen.
• Control the camera direction with eye movement.
Cursor keys

• 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
Discrete positioning controls

• in phones, TV controls etc.

– cursor pads or mini-joysticks
– discrete left-right, up-down
– mainly for menu selection
 display devices

bitmap screens (CRT & LCD)

large & situated displays
digital paper
 bitmap displays
• Screen is vast number of coloured dots
• A bitmap display shows images on the screen using tiny dots
called pixels.
Each image (text, icon, photo, etc.) is broken into a grid — and
each pixel in that grid has its own color and brightness.
• How Bitmap Display Works (Simple View):
• The screen is made up of rows and columns of
pixels.
• Each pixel has a color (like red, green, blue).
• The computer stores all this in memory as a
bitmap (a "map" of bits).
resolution and colour depth
• 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
anti-aliasing
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
• Jaggies are the stair-step or zigzag appearance
you see on diagonal or curved lines on a computer
screen.
Why do jaggies happen?
• Screens use a grid of square pixels to draw
images.
• When trying to draw a diagonal line, the computer
can only light up whole square pixels.
• This results in a stepped appearance, rather than
a smooth line.
• Anti-aliasing is a technique used to smooth jagged
edges in digital images, text, or graphics.
 Cathode ray tube
• 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
• A Cathode Ray Tube (CRT) is an old display technology that was
used in televisions and computer monitors before flat screens like
LCD and LED became common.
electron beam

electron gun

focussing and
deflection

phosphor-
coated screen
Health hazards of CRT !
• 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).
X-Rays
• Why it happens: High-voltage electrons striking the inside of the CRT
can generate X-rays.
• Danger?
– Most X-rays are absorbed by the front glass screen (specially
treated for safety).
– But some leakage can occur at the rear of the monitor.
UV and IR Radiation (from Phosphors)
• When electrons hit the phosphor coating, they can emit ultraviolet (UV)
and infrared (IR) radiation.
• Danger?
– Levels are insignificant and pose no real health risk to users.
Electrostatic Fields
• A static electric field builds up on the CRT screen and leaks into the air.
• Affected by:
– Distance from screen
– Room humidity (dry air increases static)
• Danger?
– Can cause skin irritation or rashes in some users (due to dry air + static).
– May also attract dust, increasing eye irritation
Health hints …

• 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
Liquid Crystal Displays LCD
• Smaller, lighter, and … no radiation problems.

• Found on PDAs, portables and notebooks,

… and increasingly on desktop and even for home TV

• also used in dedicted displays:

digital watches, mobile phones, HiFi controls

• 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
– light reflected not emitted => less eye strain
•LCDs are lightweight, thin, and compact.
•They emit no radiation, making them safer for prolonged use.
•Commonly used in:
PDAs, laptops, and portable devices
Desktop monitors and TVs
Watches, mobile phones, Hi-Fi equipment
special displays

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
large displays

• 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
situated displays

• 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 screem
• in all cases … the location matters
– meaning of information or interaction is related to
the location
 Hermes a situated display

• small displays beside office doors

• handwritten notes left using stylus
small displays
•beside
office owner reads notes using web interface
office doors

handwritten office owner

notes left reads notes
using stylus
using web interface
Digital paper, also known as interactive Digital paper
paper, is patterned paper used in
conjunction with a digital pen to create
handwritten digital documents. The
printed dot pattern uniquely identifies
appearance
the position coordinates on the paper.
The digital pen uses this pattern to
store the handwriting and upload it to a
computer
cross
section

• what?
– thin flexible sheets
– updated electronically
– but retain display

• how?
– small spheres turned
– or channels with coloured liquid
and contrasting spheres
– rapidly developing area
Digital paper, also known as interactive
paper, is patterned paper used in conjunction
with a digital pen to create handwritten digital
documents.[1]
The printed dot pattern uniquely identifies the
position coordinates on the paper.
The digital pen uses this pattern to store
handwriting and upload it to a computer.

The dot pattern is a two-dimensional barcode;

the most common is the proprietary Anoto dot pattern.
In the Anoto dot pattern, the paper is divided into a grid with a
spacing of about 0.3 mm, a dot is printed near each intersection
offset slightly in one of four directions, a camera in the pen typically
records a 6 x 6 groups of dots.
virtual reality and 3D interaction

positioning in 3D space
moving and grasping
seeing 3D (helmets and caves)
 Virtual Reality (VR):
Virtual Reality is a computer-generated simulation of a 3D environment that can
be interacted with in a seemingly real or physical way by a person using special
electronic equipment.
Key Features:
• Immersive: You feel like you’re "inside" a different world.
• Uses Headsets: Devices like Oculus, HTC Vive, or PlayStation VR.
• Interactive: You can look around, move, and touch virtual objects (with
controllers or sensors).
 3D Interaction
• 3D Interaction refers to how users interact with objects and navigate
in 3D virtual environments.
• Includes:
• Positioning in 3D space
– Your body, hands, or eyes are tracked in 3D (x, y, z).
– Helps the system know where you are and what you’re looking at.
• Moving and Grasping
– You can walk, fly, pick up, throw, or manipulate virtual objects.
– Often done using VR controllers, gloves, or motion sensors.
• Seeing in 3D
– Head-Mounted Displays (HMDs): Show two slightly different images
to your eyes to create depth.
– CAVEs: Rooms with screens on all sides, surrounding you in visuals.
positioning in 3D space

• cockpit and virtual controls

– steering wheels, knobs and dials … just like real!
• the 3D mouse
– six-degrees of movement: x, y, z + roll, pitch, yaw
• data glove
– fibre optics used to detect finger position
• VR helmets
– detect head motion and possibly eye gaze
• whole body tracking
– accelerometers strapped to limbs or reflective dots
and video processing
pitch, yaw and roll

yaw

roll
pitch
3D displays

• 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.

also see extra slides on 3D vision

VR headsets

• small TV screen for each eye

• slightly different angles
• 3D effect
VR motion sickness

• 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
simulators and VR caves

• scenes projected on walls

• realistic environment
• hydraulic rams!
• real controls
• other people