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Most PDAs are made of some sort of metal but some of the cheaper versions are in plastic with plastic styluses. A stylus is a pencil-like implement with a blunt end used to navigate on the touch sensitive screen and to input data. Covers may or may not be provided but are essential to prevent inadvertent damage. The size of Handheld PDAs can vary from 76 x 112 x 18mm to 189 x 95 x 34mm and their weight from 128g to 520g.
The PDAs screen is like a personal computer's monitor: it is used to display the Graphical User Interface (GUI), which in turn allows the user to operate the device. PDAs usually have touch (or pressure) sensitive screens, which allow the PDA to be operated by stylus or touch control.
The screen sizes are around 8 - 12cms long and 6 - 8cms wide, usually in portrait mode but sometimes they are landscape. Their resolutions vary and they may or may not be back, front or side lit with colour.
Good quality is important, with a high resolution (the more 'dots' that make up a picture, the better the picture), colour depth (the more colours that can be displayed can make things appear clearer, sharper etc.) plus clear screen lighting.
These are used to execute functions such as cursor/focus navigation, quick start buttons for applications, power switches. They tend to be at the bottom of the body of the PDA, small and conspicuously lacking in tactile detail which is often a problem for those with visual impairment. Sadly very few PDAs offer the alternative of a jog dial at the side of the device which is often easier to use.
Batteries are used to power a PDA and in most cases there is a single fixed rechargeable battery.
Most PDAs have two types of Memory:
The microprocessor is a computer processor on a chip. This is the part of the PDA that is used to 'drive' the device. It is synonymous with an engine, in that it is used to control all aspects of the PDAs use, dealing with the maths, driving the operating system etc. T he latest models of both Palm and Pocket PC are using Intel 400-416MHz XScale Processors with Palm OS Garnet (v5.4) OS and Pocket PC 2003 respectively.
These are the drives or slots that allow additional memory or peripheries to be added.
PDAs usually have a connection port that allows the device to be 'synched' with a desktop computer via a data cable. Most PDAs also have IR (Infra Red) for PDA to PDA (Mobile Phone or desktop) communication. Many also support Bluetooth communication between devices.
These are provided with the device to allow for data to be transferred between a PC and PDA. Some manage this through IR, Bluetooth or a single cable but most require the body of the PDA to be slotted into a cradle which is also linked to an AC adaptor in order to recharge the battery. This can be fiddly and it is worth trying out a few cradles and checking on their type of connection before purchasing the PDA.
Most PDAs have some means of alert, such as speaker for producing alarm sounds, a Light Emitting Diode (LED) for visual stimuli and/or sometimes a vibrating feature.
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