LOS ANGELES (Bloomberg) Apple Inc. chief executive officer Steve Jobs introduced three thinner versions of the iMac desktop that may push computer sales to a record during the back-to- school shopping season.

"We think these models will be very popular," Jobs, 52, said yesterday at an event at Apple's Cupertino, California, headquarters. The two 20-inch models and the 24-inch version are all made of aluminum and glass, which is easier to recycle, said Jobs, clad in his trademark black turtleneck and jeans.

Updated iMacs should spur educational orders and push Mac shipments to a record 1.9 million or more units this quarter, Piper Jaffray & Co. analyst Gene Munster said. The Mac, Apple's biggest moneymaker, accounts for almost half of sales.

"It's a very sleek-looking design," said Romeo Dator, a San Antonio-based portfolio manager at US Global Investors Inc., which has about $4.5 billion under management including Apple shares. "It's cheaper, has more power and is better looking." The 24-inch version costs $1,799, $200 less than its predecessor.

Apple shares climbed 75 cents to $136 at 2.13 p.m. New York time in trading on the Nasdaq Stock Market. Before yesterday, they had gained 59 percent this year.

Apple's world-wide personal computer market share reached a high of three percent in the second calendar quarter, up from 2.5 percent a year earlier, Munster said, citing data from researcher IDC. The company's other businesses include the best-selling iPod media player and the iPhone, which blends the iPod's capabilities with those of a mobile handset and made its debut on June 29.

Jobs won customers by updating Mac notebook and desktop machines with faster chips from Intel Corp. over the past year. Minneapolis-based Munster, who rates the shares "outperform" and doesn't own any, said in a report yesterday that a new iMac may draw attention away from the iPhone and back to the "more significant story" of the computer business.

New MacBook notebooks led a 73 percent surge in profit last quarter. The company sold 270,000 iPhones in the last two days of the quarter, and Jobs has said he expects Apple to sell 1 million by the end of the device's first full quarter of sales.

The company will discontinue its 17-inch iMac model, Jobs said. Apple also updated the iLife software that comes with every Mac, which includes applications for photos, DVD and video. All three new iMacs, which also have thinner keyboards, are available as of today, he said.