Smaller iPad unveiled at Apple event in Calif.

The walls of the California Theater are decorated with an Apple logo in San Jose, Calif., Tuesday, Oct. 23, 2012. Apple is holding an event Tuesday to announce new products.

SAN JOSE, Calif — Apple introduced a smaller iPad today, as expected, but also updated its full-sized one. It also unveiled new Mac computers, including a 13-inch version of a MacBook Pro with sharper, “Retina” display.

With a screen measuring 7.9 inches on the diagonal, the iPad Mini is about two-thirds the size of the regular iPad. It’s slightly larger than the 7-inch tablets from Amazon.com Inc. and Google Inc. The regular iPad is 9.7 inches.

The smaller tablets will start around $329.

Apple has sold more than 100 million iPads since their debut in April 2010. Although Apple dominates the worldwide tablet market with 70 percent of shipments in the second quarter, according to IHS iSuppli, Amazon and Google have been able to make in-roads with the smaller alternatives. A smaller iPad from Apple Inc. could help the company cement its dominance.

Apple also announced a new version of its iMac desktop computer that’s one-fifth the thickness of the old model around the edges. At 5 millimeters around the edges, the new iMac is thinner than most stand-alone computer monitors. It bulges in the back, however. Apple marketing chief Phil Schiller did not say how much.

The new model achieves its severe thinness in part by eliminating the optical disc drive. Apple has been leaving those drives out of its most recent laptop models as well.

An iMac model with a 21.5-inch screen will start shipping in November for $1,299 and up, Schiller said. A 27-inch version will start at $1,799.

The event at the California Theatre comes a few days before Microsoft Corp. starts selling a new version of its Windows operating system, one designed to work well on both traditional computers and tablets. Microsoft is also releasing its own tablet, the Surface, on Friday. It will be slightly larger than the full-sized iPad.

Apple’s event kicked off at 1 p.m. EST.

“We have some fond memories here, and we’re going to create a few more today,” CEO Tim Cook told the audience.

He began the presentation with a customary update on past products.

Cook talked about the success of the iPhone 5 and the new iPod Touch, both released last month. He said there have been 3 million iPod Touches sold.

He also talked about an upgrade to Apple’s software for mobile devices, iOS 6. He said there were now 200 million devices running iOS 6.

He said the app store had more than 700,000 apps, including 275,000 for the iPad. Customers have downloaded more than 35 billion apps, he said.

He touted an e-book app called iBooks and announced a new version with a new reading option: continuous scrolling. With that, you keep scrolling down the screen rather than flip pages to keep reading. You can also tap on a quote to share instantly on Facebook or Twitter.

Separately, a research group is forecasting that sales of smaller tablets will double this year thanks in part ot the mini iPad.

IHS iSuppli said today it expects about 34 million smaller tablets will be sold worldwide in 2012, up from 17 million last year. IHS defines it as tablets with screens of about 7 inches diagonally. That includes Amazon.com Inc.’s Kindle Fire, Barnes and Noble Inc.’s Nook Tablet and Google Inc.’s Nexus 7.

The research firm says sales should double again next year to 67 million.

As a percentage of all tablets, the smaller ones are expected to account for 28 percent of 2012 sales, compared with 24 percent in 2011.

See Wednesday’s editions of The Post and Courier for more details.