Firm foundation in the main hci principles, the book provides a working

Figure 4.10 The Microsoft
®
Metro–style interface that unifies the mobile and desktop 
interaction.
Figure 4.11 (Left) Obscure Google Chrome browser icon design (difficult to tell at a glance what 
the icon represents) vs. (right) informative icon design for the Angry Birds application (the visual 
imagery of an “angry bird” is well captured).

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6 8
H U M A N – C O M P U T E R I N T E R A C T I O N 
organized as a one-dimensional list or a two-dimensional (2-D) 
array of items (represented in text or as icons/earcons).
Selection of a menu item involves three subtasks: (a) acti-
vating the menu and laying out the items (if not already acti-
vated by default), (b) visually scanning and moving through 
the items (and scrolling if the display space is not sufficient to 
contain and show the whole menu of items at once), and (c) 
choosing the wanted item. All of these subtasks are realized 
by making discrete inputs, e.g., by mouse click, screen touch, 
button push, voice command, etc.
Menus (i.e., lists of items) may be presented in a variety of 
styles and mechanisms, as seen in Figure 4.12. Some of the 
most popular ones are shown in Figure 4.13: the pull-down, 
pop-up, toolbars, tabs, scroll menu, 2-D array of icons, but-
tons, check boxes, hot keys, etc. Table 4.1 shows how to best 
use these different types of menus.
(a)
(c)
(d)
(b)
(e)
Figure 4.12 Different styles of menus 1: (a) pull down, (b) pop up, (c) 2-D application bar, (d) 1-D 
toolbar, and (e) tabs. (From Petzold, C., Microsoft XNA Framework Edition: Programming Windows 
Phone 7, Microsoft Press, 2010 [4].)

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6 9
H C I D E S I G N
The menu items are usually subtasks to be invoked or the target 
interaction objects for certain tasks to be operated upon. In either 
case, it is clear that the menu must be organized, categorized, 
and structured (typically hierarchically) according to the task and 
the associated objects. At each level of the menu, the number of 
items should be managed to be ideally below the “magic num-
ber 8” (the limit of our short-term memory, discussed in Section 
3.1.2) [6]. However, it may not always be possible to achieve