Glowing trademark blue and orange, a portable version of Apple Computer Inc.'s quirky iMac machine made its debut today, a much-awaited addition to the resurgent computer maker's ongoing reinvention.

Steve Jobs, Apple's mercurial co-founder, introduced the iBook laptop to a boisterous crowd of Apple loyalists at the MacWorld Expo trade show at the Jacob Javits Convention Center here.

The machines weigh 6.5 pounds and will cost about $1,600 when they hit store shelves in September. For an extra $400, people will be able to buy equipment that will allow them to cruise the Internet wirelessly as they move the machine around their homes.

As important as the features, however, is the look. With a distinctively round shape and rubberized exterior, the iBooks, some attendees said, look like portable toilet seats. Others said they resemble giant clams.

Either way, iBooks don't look like traditional laptops, and that neatly suits Apple's "Think Different" ideal, as well as its oft-stated focus on school and consumer markets.

In other words, be damned the less flashy, less colorful tastes of laptop-dependent business travelers.

"Not a lot of businesspeople would be caught dead with an iBook," added Tim Bajarin, an analyst at the computer consulting firm Creative Strategies Inc. in San Jose. Still, Bajarin predicts the iBook will be "another blockbuster" and credits Apple with defining the market for consumer portable computers.

Early returns on the iBook were stellar, though the semiannual MacWorld gathering tends to gather a fiercely pro-Apple crowd. "I'm totally blown away," said Joe Ryan, editor of MacLaunch, an Internet portal for the Mac faithful. "I love the things," added John Van Sickle, an Emory University student en route to a pay phone to order an iBook. (Apple is taking orders for the laptop, but won't start shipping them until September.)

Wall Street's reaction was also enthusiastic. Shares of Apple rose $1.18 3/4 today to close at $54.06 1/4. Stock of the Cupertino, Calif.-based company, which reported its seventh consecutive profitable quarter last week, has soared by more than 60 percent in the past three months.

The iBook debut highlighted Jobs's 90-minute keynote speech in a packed auditorium the size of an airplane hangar. Hundreds of Mac fans were left waiting in line outside as actor Noah Wyle came on stage to open the show. Wyle, a Jobs dead ringer who played the Apple chief in a recent TV movie, mimicked Jobs for a few minutes before the real thing walked out and yelled "Cut!"

As Wyle shuffled off, Jobs marveled that it wasn't even a year ago--the anniversary is Aug. 15--that Apple shipped its first iMac, the colorful, hood-shaped PCs that have become synonymous with the company. "IMac is going gangbusters," Jobs said, noting that Apple has already shipped 2 million iMacs.

IBook will also feature wireless networking capabilities. By purchasing a $99 "Airport" card and a $299 "base station," an iBook owner can wander as far as 150 feet from the base station and stay connected.

Some Apple watchers had speculated that the company would introduce a hand-held computing device today, but it did not--and company officials said nothing was forthcoming. "That stuff is not a priority," said Phil Schiller, Apple's vice president for worldwide product marketing, dismissing such predictions as "Web rumor junk."

CAPTION: Some have said the iBook looks like a toilet seat, or a giant clam.