Information Technology Reference
In-Depth Information
213 188
186 149
162 128
149 136
149 136
164 140
164 140
155 129
151 124
131 156
QWER T Y U I
O P
Same
Hand
Alternate
Hand
180 140
196 147
222 138
201 135
201 135
175 120
175 120
162 133
194 141
Key
S
A
D
F
G
H
J
K
L
162
241
238 153
197 153
197 160
157 132
157 132
249 164
235 159
Z
X
C
V
B
N
M
,
.
155
All keystrokes
average: 155 ms
Space Bar
Fig. 3.6 The time (in milliseconds) to type different keys on the keyboard based on
155,000 keystrokes. Times taken from Kinkead ( 1975 ) cited in Card et al. ( 1983 ). Same hand
times are for keys typed with the same hand; alternate hand is for keys typed after a key typed by
the other hand
3.3.2 Touch Screens
Probably the best-known and most widely used devices that support haptic input
are touch screens. These are now commonplace on many mobile devices (smart-
phones, tablet computers, and so on) and in information and ticket sales kiosks.
Feedback for these devices is mostly provided through visual and audio channels.
Figure 3.7 shows two examples of touch screen applications, one of which is static
(an e-voting system), and the other highly portable (a handheld GPS satellite
navigation system).
Touch screen displays are electronically more complicated than normal dis-
plays because they use either pressure or electrical conductance to determine
where the screen is being touched. If the interface is well designed, it will be very
clear to the user what actions they have performed on the screen (selection,
scrolling, and so on), and the interface will be easy to use, and easy to learn to use.
There are many examples of videos online, for example, that show young children
figuring out how to use touch screen devices without any instruction.
The end of the finger is of the order of ten times the size of the normal
arrowhead cursor that you see on most systems. You will need to take this, and
individual variations in finger size, into account when designing touch screen
interfaces to avoid fat finger problems. These occur when people touch more than
one button at a time, or accidentally touch the wrong button. It has been calculated
that about 9% of clicks on adverts on mobile devices are accidental! 2 So, if you
need to accommodate many buttons on a small touch screen, you will need to have
a deeper understanding of how the technology works and the ways in which users
use small buttons.
2
http://econsultancy.com/uk/blog/10649-mobile-s-biggest-ad-challenge-fat-fingers
 
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