Chapter 2: Trends Towards Mobility 17 4 tasks. A mobile device should be small and light; it should fi t nicely into the user’s hand and pocket. It should be easy to carry at all times. Some devices may be worn in arm or wrist bands or carried on neck straps or belt holders. Mobile devices can be considered as information appliances that are computer-enhanced consumer devices dedicated to a restricted cluster of tasks (Bergman 2000). They are notably different from desktop PCs, in that they have limited functionality targeted only to specifi c tasks, they are not upgradeable, but are perceived to be less expensive and less complicated to use. We can divide mobile devices into three categories: 1. dedicated media devices; 2. Swiss army knives; and 3. toolbox devices. We categorize the devices based on the number of functions (or features) and their versatility rather than by shape, form, and wearabil- ity or carryability. Among other features, these have a major infl uence on the user interface design, as described in Chapter 6. Such a catego- rization also aids in analysing the evolution of mobile devices – when the functionality increases, the devices eventually move from one category to another. Next, we introduce the characteristics of each category, and provide examples of devices in each of them. 2.2.1 Dedicated Media Devices As the name of this category implies, a dedicated media device is designed for a single purpose in such a way that its functionality cannot be extended or upgraded further. Such devices are mainly intended for getting (creating) or enjoying one type of content. These devices may have additional, secondary features (for example, an MP3 player with a radio receiver, or a digital camera with a display for previewing the images), which support and complement the limited number of primary tasks. A common characteristic for these devices is that the user does not manage content with them. New functions cannot be added, except by the manufacturer after a new device generation is introduced, so this class cannot be used for 4 For further discussion related to mobility, see http://opengardensblog.futuretext. com/archives/2006/01/