By The Associated Press

LOS ANGELES — Microsoft has unveiled Surface, a tablet computer to compete with Apple’s iPad.

CEO Steve Ballmer was on hand Monday to announce the new tablet, calling it part of a “whole new family of devices” the company is developing.

One version of the device, which won’t go on sale until sometime in the fall, is 9.3 millimeter thick and works on the Windows RT operating system.

It comes with a kickstand to hold it upright and a touch keyboard cover that snaps on using magnets.

The device weighs under 1.5 pounds and will cost about as much as other tablet computers. Its debut is set to coincide with the upcoming fall release of Microsoft’s much-anticipated Windows 8 operating system.

Steven Sinofsky, president of Microsoft’s Windows division, called the device a “tablet that’s a great PC —a PC that’s a great tablet.”

A slightly thicker version —still less than 14 millimeters thick and under 2 pounds — will work on Microsoft’s upcoming

Windows 8 Pro operating system and cost as much as an Ultrabook, the company said.

The pro version comes with a stylus that allows users to make handwritten notes on documents such as PDF files.

Each tablet comes with a keyboard cover that is just 3 millimeters thick. The kickstand for both tablets was just 0.7 millimeters thick, less than the thickness of a credit card.

Microsoft has been making software for tablets since 2002, when it shipped the Windows XP Tablet PC Edition. Many big PC makers produced tablets that ran the software, but they were never big sellers. The tablets were based on PC technology, and were heavy, with short battery lives.

Microsoft didn’t say how long the Surface would last on battery power.

Microsoft’s decision to make its own tablet is a departure from the software maker’s strategy the personal computer market.

With PCs, Microsoft was content to leave the design and marketing of the hardware to other companies, such as Hewlett-Packard, Dell, Lenovo and Acer, that licensed the Windows operating system and other software applications.

The more hands-on approach with its tablet indicates that Microsoft either lacks confidence in the ability of its PC partners to design compelling alternatives to Apple’s iPad or it believes it needs more control to ensure Windows plays a major role in the increasingly important mobile computing market.

Whatever Microsoft’s motives, the company’s tablet plans risk alienating some of its longtime partners in the PC industry