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chapter 2
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
- mouse/trackpad
- variations
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
?
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?
cable/satellite TV
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
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
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)
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!
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
