Input
The input on a PDA works via the touch screen, constructed of a layer of nonconductive gel or oil sandwiched between a layer of plastic and a layer of glass.
Current is applied to silver ink strips along the vertical and horizontal edges of the glass. When you push down with your stylus, the plastic touches the glass, changing the voltage field, and the touchscreen driver records a touch.
PocketPC has handwriting recognition, supporting "normal" handwriting, which works fairly well as long as you write reasonably neatly. It also has a single-letter recognition mode similar to Palm's Graffiti.
The Toshiba has the transcriber, which allows you to write anywhere, similar to the old Apple Newton, giving you the ability to write at whatever size you like.
A pop-up keyboard is also available, allowing you to tap out your input with the stylus on a virtual keyboard, but this is fairly time consuming to use regularly.
The Zaurus control panel also slides down to reveal a small qwerty keyboard which can be used for input, and a function key provides various symbols. You could probably become quite proficient at typing with your thumbs after a bit of practice.
Qtopia on the Zaurus supports plain handwriting recognition with a similar interface to the PocketPC. The handwriting recognition wasn't as good as with Pocket PC (although we had an early developer model) but it includes a handwriting trainer so you can learn to write letters the way Zaurus recognises them.
There is also the option to create personalised character templates so that the Zaurus will recognise letters the way you write them.
There is the pop-up keyboard, and a QT innovation called the pickboard, which works similarly to modern mobiles--you select the letter groups and it suggests words that can be made from the series of letters you have typed. Some people may find this faster than typing on the pop-up keyboard.
For text input the PalmOS uses Graffiti, which is a set of stylus strokes mapped to letters and symbols. This takes a little longer to learn, but 15 minutes will teach you the basics and with even moderate use you soon become proficient.
The pop-up keyboard is also available, but with Palm's generally smaller screen this can cost you a bit of real estate.
All the devices we tested had buttons on the case to select the usual PDA functions like address book and calendar.
The Zaurus and Toshiba both had control pads to move the cursor around and scroll around documents, which is also clickable. The Zaurus also has an OK button which replicates the OK button on the title bar of applications and closes them.
Power
Modern handhelds generally have internal rechargeable batteries. All the models we tested had lithium ion batteries, except the Palm m505, which had a lithium polymer battery.
The lithium polymer battery (LPB) was produced by a consortium headed by 3M, in an effort to produce a lightweight battery for electric cars.
Ultra thin and flexible, the LPB replaces the electrolytic liquid or gel of a normal lithium battery with a sheet of polymer, eliminating the risk of flammability and leakage. According to the details provided by the manufacturer, the life of the LPB is equivalent to a normal lithium ion battery.
The battery life of the Palm and Visor machines is rated in weeks. This is due to the light operating system and low power usage of the 68k processor.
The other machines all came in at around eight hours of normal use. Given that on most units there is no easy way to replace the flat battery with a charged one, we felt that this was a little bit of a limitation in certain circumstances.
One of the scenarios we considered for handheld computers was to collect survey information in public or door-to-door. This would require a full day of constant use, whereas normal use would be more like turned on for five minutes every half an hour or so.
The shorter battery life would require the user to be tied to a cradle regularly to recharge the device, which takes a few hours.
One advantage is that the Toshiba Pocket PC, HP Jornada and Sharp Zaurus both have a socket for power, which would at least give users limited mobility while connected to power, but the other devices tested all needed to be in their cradle to charge.
