When is a laptop no longer a laptop?

When it's thin enough to fit in an office envelope, as Steve Jobs might have it? When the screen size is trimmed so brutally that a woman can truly contemplate putting it in her handbag? When its internal organs are squashed so tight that it really doesn't have the power you might expect of a regular PC?

A test drive of the new Asus Eee PC 901 - the latest in a line of mini-laptops - confirms that there is now a category of computer which combines the basic functionality of a laptop with the connectivity and portability of a BlackBerry.

The only drawbacks are a slight dip in functionality, and the occasional feeling that things seem a little squished. In a device the size of a hardcover book, and costing a shade over £300, both are eminently tolerable.

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The PC 901 is the latest model in what is easily one of the most awkwardly named family of devices in history - the 'Eee' range by ASUSTeK . It's about an inch thick, weighs 1.1kg, and feels sturdy enough that it could be sloshed about in a regular bag without much harm coming to it.

It has a nine-inch screen - a little under two thirds the 14-inch average of most laptops - and is by no means conducive to watching films, or playing high-end games. Indeed most applications, including those that you would use often, like word processing, feel a little compressed.

But without a CD drive and with only 12GB of internal memory, the 901 is never going to be a replacement for your existing PC. The machine is designed principally one goal in mind - to give you all the basic computer functions - word processing and browsing - in a tiny parcel when you're on the go. And in this task it excels.

The Eee PC 901 comes in white or black, and under the bonnet is a fully functional Windows XP. (For those who are aren't overly Microsoft-dependent, there is the option to get a version which runs Linux and gives an extra 8GB of memory in the solid state drive - such is the bulk of Windows.)

The internet is accessed by wi-fi, or via a USB dongle that connects to the web using the mobile network. There are three USB ports, which means in theory you could be charging your iPod, uploading photos from your camera and surfing the web - all at the same time.

For the mobile worker who has frequently wrestled with limited time in the hotel - and a jumble of power cords in the suitcase - this will be a blessing. Battery life is billed at just under eight hours.

The keyboard is tiny. The keys - which measure about a centimetre square - are struggle for those with slender fingers, let alone the fat of thumb, and you might find yourself missing letters relatively often.

The left mouseclick is also annoying. Holding down to drag and drop, for instance, requires much more pressure than it should. But this is partly made up for by some nice features in the built-in mousepad, for instance: dragging two fingers down in parallel translates to a downward scroll, and vice versa. (Apple users will recognise this from the Macbook line.)

There's no built-in microphone - which is a setback for bloggers who like to do audio. The speakers also offer less volume than they might. There is, however, a 1.3 megapixel camera, which will manage video chat on Skype.

At £319 - it's not exactly the cheapest option. There are a plenty of sub-£300 laptops available. There is also healthy competition in the nine-inch laptop market, including the HP Mini-Note, and the MSI Wind.

But if you're one of the new class of ultra-mobile workers who need a "day machine" to do more than just check e-mail - and for whom portability is an issue, you could do worse than pick up an Eee PC 901 as a second computer. Provided, of course, you're willing to take a little more care with your typing.

Verdict: compact, well-connected, but at times a little compressed

*Those who like the sound of the 901 but want a slightly bigger screen should be aware a 10-inch version of the device - which was unveiled at a conference in Taiwan recently - is due out soon.

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