Small may be beautiful - but unusable

EVERY new electronic gadget promises as many functions as a Swiss army knife, whether they are useful or not. Take the new Xda II from the mobile-phone company 02. This silver beauty is a powerful Windows Pocket PC with camera, multimedia messaging, games, music, office software, e-mail and internet access. Oh, and it is a mobile phone as well.

Actually, using it as a phone is what it is worst at, unless you enjoy holding something slightly smaller than a family-sized bar of chocolate to your ear. As the smartphone incarnation of the personal digital assistant (PDA), though, it is pretty good, and if I wanted to spend 350 plus monthly subscription I might be tempted.

Designers of PDAs have always had to compromise between size and function. Nobody could use a device which showed web pages on a screen the size of a postage stamp, although some manufacturers of smartphones seem to be trying.

Palm developed the standard PDA design in the mid-1990s. Essentially, it uses a playing card-sized display; a narrow frame with half-a-dozen buttons along the bottom. A stylus can be used as a mouse on the touch-sensitive screen or to enter data either using handwriting recognition or by tapping on a minuscule keyboard display. It is fine for notes, but not novels.

Other PDAs were designed along the lines of a miniature laptop with a real, if tiny, keyboard, a style recently revived in the dazzling Sony Cli. It was also the route followed by Britain’s Psion until it stopped making PDAs to concentrate on software. Now there are two dominant flavours of PDA, Palm and, inevitably, Microsoft. But Psion is far from down and out. Symbian, its joint venture with the world’s leading mobile-phone companies, runs a large proportion of the new breed of "smartphones". The two other main players are ... Palm and Microsoft. The PDA is dead, long live the smartphone. Maybe.

I am slightly sceptical about phones that promise to do everything. For instance, many of us have become horribly dependent on e-mail and would like access to it on the move. Plenty of PDAs and smartphones provide this facility, but try responding to an e-mail on, say, a moving train. Unless you have the texting ability of a teenager, tapping away with a stylus on a tiny screen keyboard or producing recognisable handwriting is as easy as stacking ball bearings.

The only pocket-sized gizmo I have come across that is up to receiving and responding to e-mails is the BlackBerry - and that is because it was designed to do just this one task.

Roughly the size of a floppy disk, it has a small, but very clear, screen at the top and a keyboard at the bottom. This layout makes it surprisingly easy to type, holding the BlackBerry in two hands and using your thumbs.

The BlackBerry has cult status in the United States, but has been hard to get hold of here until quite recently. Now, companies such as Isis (isistelecom.com) have made them available without a long wait, although it is still not cheap.

Another device that is different from the rest is the Palm-powered Dana wireless. With its full-size keyboard and a screen more than three times larger than most PDAs, it will not fit any pockets. But for many people it would make a cheap (309 plus VAT) laptop alternative with all the benefits of Wi-Fi connectivity. All that lets it down is the screen, which is hard to read in less than perfect light.

No PDA or smartphone is going to replace a full-sized computer. Anybody thinking of buying one should think carefully about what it is going to be used for: small may be beautiful but unusable, while large is not much use if it is left on the desk. If you are not sure, maybe you should get a Filofax.