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Input method

From the application perspective, a user interacts with GUIs through different input methods, and uses a certain input method to interact with a certain type of window. Table XI provides the energy consumption for different input methods on the targeted handheld computers. It also shows the number of stylus taps an input method is equal to (denoted by #) with regard to energy consumption. The stylus tap is the most commonly used input method. Hardware buttons are used to trigger the most-used applications. Virtual keyboard is necessary for text input (Zaurus also comes with a mini hardware keyboard we do not characterize in this work). Stylus move is typically used to move a window like a scroll bar.

Table XI: Additional energy for different input methods
Input method Qt Windows X/GTK
EU # EU # EU #
Stylus tap 1,100 1 300 1 900 1
Hardware button 1,400 1.3 560 1.9 1,300 1.4
Virtual keyboard 4,000 3.6 4,700 15.7 1,200 1.3
Stylus move $ \sim$13,500 $ \sim$12.3 $ \sim$5,700 $ \sim$19.0 $ \sim$3,000 $ \sim$3.3

A stylus move is very expensive in all three systems. Moreover, it is usually associated with continuous screen changes such as window moving and resizing, for which the energy cost is significant. Moreover, a virtual keyboard is very expensive on iPAQ1 and Zaurus because they have the auto-completion feature in order to accelerate user input. Since reducing usage time saves a significant amount of energy, auto-completion is generally more energy-efficient. However, inputting text is much slower using a virtual keyboard than a real keyboard. Thus, it increases usage time significantly on handheld computers, and leads to more energy consumption from the application perspective. For energy efficiency, stylus move and text input should be minimized.
next up previous
Next: GUI platform comparison Up: GUI energy characterization Previous: Color patterns
Lin Zhong 2003-10-13