Once seen as toys or gadgets for people with more money than sense, today’s handheld computers are not only far more affordable, they also offer a wide range of features including email and internet access. Some models even double up as mobile phones.

If you’ve never used a handheld before, you’ll soon wonder how you lived without one. And if you’ve used one for some time, you’ll be amazed by the size, power, performance and features offered by the latest models.

Handhelds can be split into two main groups. First there are personal digital assistants (PDAs) - essentially electronic organisers with a few extra bells and whistles. Most include address book, calendar and to-do list applications, with details usually entered via a touch-screen and stylus. The second group is handheld PCs, which offer address book and diary features, too, but can often also run word processing and database applications, and a growing number offer optional email and internet access.

One of the most useful features is the ability to synchronise your handheld and your desktop computer, allowing you to transfer data between them. If you want to do this, make sure that the handheld is compatible with your computer, as some models only work with PCs.

These days, colour screens are becoming standard, not least because many handhelds are also multimedia devices that can display colour graphics, still images and video clips. However, colour screens use extra battery power, so if you only want to store text information, a model with a monochrome screen will be cheaper and run longer.

One feature of the handheld market that hasn’t changed is the wide variation in what you get for your money. Some manufacturers are generous, supplying items like connecting cables or a hot-sync cradle - which makes it easier to connect your handheld to a computer - as standard. Others make these optional extras. If you want to use features such as email, you’ll probably need to buy a plug-in modem card and get a contract with a mobile phone company.

In fact, it’s difficult to know where a handheld computer starts and a mobile phone ends, as some handhelds also have telephone features. Hewlett Packard’s Jornada 928 (pound;390 plus a contract with Vodafone) can operate as a GSM (the global mobile operating standard) or GPRS phone or modem - GPRS offers a high-speed, always-on internet connection. It also allows multimedia messaging, internet audio downloads, video playback and you can use a voice-dialling system. Handspring’s Treo 270 (pound;499 with a contract with Orange) offers a GSM mobile phone, wireless email, text messaging, internet access and a Palm organiser in a device weighing just 153 grammes. It can also be upgraded to GPRS.

Many handheld computers use infrared (IR) to beam information from one device to another. Some use Bluetooth, which is also wireless. For around pound;500, the Compaq Ipaq H3970 includes built-in Bluetooth technology (many Bluetooth-compatible handhelds use expansion cards) and it can exchange information with Bluetooth-enabled PCs, printers and mobile phones.

As well as doubling as mobile phones, some handhelds can be used as portable information and entertainment devices. Sony’s Clie PEG-T675C (around pound;349) uses “memory sticks” that can store audio, data, image or video clips. It can be used with a supplied stereo headset to play MP3 music files and even acts as an IR remote control handset for selected TVs, DVDs and VCRs.

The really good news is that now you don’t have to be rich to own a handheld and there are several lower-priced models on the market. Handspring’s Treo 90 (pound;249) is a PDA which includes a colour screen, 16 megabytes of memory, built-in keyboard and compatibility with new SD (secure digital) memory cards, which allow you to add memory, play games, view photos, read electronic books and use Bluetooth technology. Palm’s Zire (pound;80-pound;100) includes a monochrome screen, IR beaming, rechargeable battery, desktop software for the PC or Mac and connecting cables. It’s not the best-specified model, but it’s a good place to start.

www.handspring.com

www.hp.com (also for Compaq)

www.palm.com

www.sony.co.uk

* Turn to the Bytes column on page 5 for details of how to win a Palm M125 loaded with a software package for teachers.