When it comes to performance, the palmtop is the ultimate `go anywhere' computer. Mike Hewitt on the pocket-size miracle
Can a palmtop computer ever take the place of the full-size, genuine article? Yes, but only inasmuch as a bicycle can replace a car. Sometimes it can, of course, and is often better suited to the task. Just as you wouldn't try to drive a Ferrari down a narrow mountain track, so it's impractical to tuck a 486 laptop with a protruding tracker-ball down the front of a pair of Lycra shorts. The fact is, thousands of people regard palmtops as practical alternatives, not only to laptop computers, but also to office-bound PCs. They're perfectly happy to use them for wordprocessing, spreadsheets and even e-mail.

A palmtop's ancestry owes more to the electronic calculator than to the PC, and so it remains the only true "go anywhere" computer. It is certainly the only type that is both light and small enough to fit into a jacket pocket - it is typically 6in long, 4in wide and about half an inch thick. And because it doesn't have power-hungry extras like backlighting and disk drives, the palmtop's battery life is usually at least five times that of the most sophisticated laptop - enough to keep you going around the world several times, and more, without recharging.

Where the palmtop scores over electronic diaries is that users can type on it, with a little practice. Those with nimble fingers can achieve reasonable speeds - maybe 30 words per minute - on some of the better models. Success depends on three factors. First, you need a keyboard that provides decent "tactile feedback". Second, the palmtop must be used on a steady, level surface: balancing it on your lap is out. Third, you must be able to hear a keyboard click. It is no doubt psychological, but most users report that if those clicks are turned off or drowned out by ambient noises, their typing deteriorates dramatically.

Although palmtops are generally not able to run the same programs as the office PC, the in-built programs on some models can be very good in their own right. Also, most are able to exchange data with desktop PCs. So, for example, you can start work on a document using the office wordprocessor, save it in an intermediate file format, and then transfer it across to the palmtop for further editing. And vice-versa.

A few of the better models are what are described as "systems" machines. They are marketed together with a complete range of business software, such as accounts programs, spreadsheets, and databases, as well as all the necessary peripherals, such as fax modems and connecting cables.

Probably the best, and best-known, in this respect is the Psion 3a, which costs from pounds 250 to pounds 400. Its built-in wordprocessor is as functional, if not more so, than many on conventional PCs. There is also an increasing range of programs and add-ons available, either from Psion itself or third- party vendors. These include full-blown accounts packages, language translation software, wine databases, and even maps of the London Underground.

In combination with the Psion 3 Fax pocket modem, the 3a really comes into its own. This provides full Group 3 fax compatibility (albeit, because of memory constraints, without the "receive" capability). In other words, you can compose letters using the wordprocessor, format them, and fax them out complete with cover sheets and company logos. As far as the person on the receiving end is concerned, they have been produced on a conventional PC. The 3Fax can also be used with shareware communications packages to allow access to commercial services such as CIX and CompuServe, allowing you to keep up to date with your e-mail.

Sharp's Zaurus ZR-5000, to be launched in the UK in early September, looks as if it could well give the Psion 3a a run for its money - at least, if the enthusiastic reviews from the US are anything to go by. This is intended as the successor to the IQ range of palmtops. When folded flat, the Zaurus measures barely the size of a large wallet. But its keyboard, about 80 per cent the size of that on a conventional notebook computer, is just about big enough to allow touch-typing, provided you don't have fingers like cucumbers. Other features include a powerful 16-bit processor and onboard memory of 1 Megabyte.

Perhaps the most useful feature from a businessman's point of view is that, in combination with the optional CE-FM4 modem, the Zaurus can send and receive e-mail and faxes and access on-line services. Later in the year, Sharp plans to launch a GSM phone interface, which will allow the Zaurus to send and receive data via a digital cellphone. In the United States, the Zaurus sells for about $400. The UK price will be around pounds 400.

Among other palmtops, the Hewlett-Packard 220LX (pounds 440-pounds 550 plus VAT) deserves a mention because although it has their own operating systems it can also "emulate" DOS, the system used by Personal Computers. It is thus possible to transfer a program - as long as it not too elaborate - from PC to notebook.