Handheld computer systems studied

The information on the handheld computers used in this work is summarized in Table II.

Table II: Hardware and software information on the handheld computers

	iPAQ1	iPAQ2	Zaurus
Vendor	HP/Compaq		Sharp
Model	3870		SL5500
SOC	Intel StrongARM SA-1110 206$MHz$
Storage	32MB ROM, 64MB RAM		16MB ROM, 64MB RAM
Display	240$\times$320, 16bit color, reflective with front light
OS	MS Pocket PC 2002	Familiar Linux 2.4.18	Embedix Linux 2.4.6
GUI	Windows	X/GTK	Qt

The two iPAQs are placed in the same charging cradle when energy is measured. The Zaurus, instead, is directly charged by the same AC/DC converter used for the iPAQs. Energy is measured when the batteries are fully charged. All other detachable peripherals, such as CompactFlash cards, serial and USB ports, $etc.$, are disconnected. Since no current GUI platform has an effect on the front light, it is turned off unless otherwise indicated.