Apple (Nasdaq: AAPL) on Tuesday introduced new iPads in time for holiday shoppers, as it battles to stay ahead of rivals in the increasingly crowded market for tablet computers.

Apple Chief Executive Officer Tim Cook debuted a new iPad mini with a high-definition screen, as well as a thinner and lighter design for the larger iPad named the iPad Air. The iPad Air goes on sale on Nov. 1, with prices starting at $499.

“This is just the beginning for iPad,” Cook said to a crowd of media and technology-industry insiders at the Yerba Buena Center for the Arts Theater in downtown San Francisco. “We have been busy working on the next generation of iPad.”

In the year since Apple last updated the iPad, companies including Samsung Electronics Co., Asustek Computer Inc., Google Inc. and Inc. have unveiled new tablets, often at lower prices. The competition adds pressure to Apple because the iPad is its second-largest source of revenue after its flagship iPhone. Success of the new models will be critical as the Cupertino, California-based company attempts to reignite revenue growth, which has slowed.

Apple today also introduced new Mac software, called Mavericks, which is available free of charge. The company showed an updated high-end Mac Pro desktop computer aimed at professions that need extra computing power, such as graphic design and film editing, as well as new MacBook Pro laptops.

“We still believe deeply in this category and we’re not slowing down on our innovations” in Macs, said Cook.

Tablet Slowdown?

Apple is updating its products ahead of the lucrative holiday shopping season. As part of the lineup, the company released new iPhones — the iPhone 5s and 5c — last month.

Yet more than three years after Steve Jobs unveiled the iPad, the growth of the global tablet market is showing signs of decelerating. Tablet shipments are projected to increase 28 percent in 2014 to 301 million units, after doubling in 2012, according to Counterpoint Research.

Competitors are cutting into Apple’s lead. The company’s tablet market share slid to 32 percent in the second quarter, compared to 60 percent a year earlier, according to IDC.

Samsung, Asustek, Lenovo Group Ltd., Acer Inc. and others are offering devices with prices starting at less than half of the iPad mini’s $329. introduced new Kindle Fires last month with higher-resolution screens at prices starting from $229, while Microsoft Corp. and Nokia Oyj took the wraps off new tablets this week.

‘Post PC’

Cook alluded to the competition today, noting that “everybody seems to be making a tablet.” He added that the iPad is used more than four times more than all other tablets put together. Apple has sold 170 million iPads, he said.

In a move to spur growth, Apple will also roll out the new iPad Air in China at the same time as other markets, said Phil Schiller, Apple’s senior vice president of product marketing.

The companies are trying to adjust to what Jobs called the “post PC” era, where preferences have shifted to mobile devices rather than personal computers. The shift has decimated the PC industry, with shipments of traditional desktops and laptops projected by Gartner Inc. to fall 11.2 percent this year. The shift has hampered sales at Microsoft, Intel Corp., Hewlett-Packard Co. and others.

Some rivals’ tablet efforts have flopped. Microsoft took an $900 million writedown earlier this year after its Surface failed to catch on with consumers.

Apple and other tablet manufacturers are now attempting to win over new customers, beyond consumers who use the devices to browse the Internet, watch videos or play games. School districts, government agencies, pharmaceutical sales forces, airlines and insurance companies are among those who have purchased thousands of tablets in lieu of traditional computers.