Shares in Apple Computer soared as the company announced a new laptop computer that it hopes will underpin its reversal of fortunes.

Interim Chief Executive Steve Jobs introduced a greatly anticipated consumer laptop, a portable version of the curvy, colourful iMac that has fuelled the computer company's comeback, at the MacWorld exhibition in New York.

Apple announced a year ago that it would develop the iMac-like laptop, and the cult-like following of Apple users have been engaged in intense speculation about the look specifications and release date of the new portable code-named P1.

"There has been a lot of speculation and a lot of rumours, and I get to end them today," Mr Jobs said during his keynote address at the conference.

Prices for the iBook will start at $1,599.

Shares in Apple soared by $2 to $55 on the Nasdaq stock market when the new computer was unveiled before falling back slightly.

The company's stock has seen a huge increase of more than 50% in the past few months as confidence in the success of Apple's new products has grown.

Profits to go

It is hoped that the iBook will help continue Apple's return to profitability, spurred by the popularity of the iMac.

The company has had six straight profitable quarters and has sold nearly 2 million iMacs, gaining more than 6.7% of the US retail desktop computer market in May - double its market share one year ago.

But the laptop computer market could be tougher to crack. It is mainly corporate, and the limited software applications available to business users might make some companies reluctant to purchase it.

Apple's high-end notebook computer, the Powerbook, is another problem. Apple has to ensure that its new product does not undercut sales of the older but more expensive Powerbook.

Specs end speculation

The iBook looks much like the iMac. The six-pound laptop features a colourful clamshell case.

The laptop features a handle

But unlike the iMac, the iBook will be sold only in blue or orange, and the laptop features a fold-down handle on the back of the case.

Like the iMac, it has a built-in Internet capability but no floppy disc drive. Apple claims its PowerPC processor will outperform existing Intel processors on current laptops.

Apple has been pressing hard to retain its place in the education market as it offers more appealing computers to consumers, and the iBook introduced new technologies that it hopes will appeal to both markets.

Mr Jobs emphasised wireless networking capabilities available as an option for the laptop.

"This is the first computer ever designed from the ground up for wireless communications," he said.

The laptop has two antennae built into the case, flanking the screen.

Using an optional AirPort card and base station, the laptop will be able to link wirelessly with local computer networks. The card will cost $99 and each base station will cost $400.

Up to 10 of the laptops will be able to connect to each other and to the Internet using one base station.