Palm- or pocket-sized personal digital assistants (PDAs) are portable, battery-run computing devices with simplified operating systems and applications. Most offer the ability to enter text through graphics recognition programs and to ‘synchronize’ or transfer information on the PDA to a standard computer. External keyboards can be purchased as PDA attachments to facilitate text entry. PDAs are best used as complements to desktop/notebook systems. PDAs support applications such as scheduling/date books, calculators, simplified word processing and spreadsheets, games, electronic texts/e-books, e-mail, field questionnaires and mobile reference guides.
PDAs typically run on standard “AAA” or rechargeable lithium-ion batteries. With limited daily usage, batteries commonly last two to three weeks. The PDA’s operating system and factory-installed applications are stored in read only memory (ROM), which means that these programs are stored whether or not the unit has a source of power. Data input by the user is typically stored in the unit’s Random Access Memory (RAM). Even when the PDA is turned off, RAM memory draws a small amount of current from the batteries in order to keep its memory cells charged and the data intact. The result is that PDAs run the risk of data loss even when the unit is not being used. If the power source is removed or the batteries completely lose their charge, then the user has about one minute to restore power before the data stored in RAM is lost. When using PDAs in off-grid areas it is a good idea to have regular data backup procedures in place. This is particularly important in situations where batteries cannot be reliably replaced or recharged, or when the PDA may remain unused for a few weeks.
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