Microsoft Surface Microsoft has unveiled Surface, a tablet computer to compete with Apple's iPad.

Chief executive Steve Ballmer was on hand to announce the tablet, calling it part of a "whole new family of devices" the company is developing.

The 1/3-inch (9.3 millimetre) thick tablet comes with a kickstand to hold it upright and keyboard that is part of the device's cover. It weighs less than one-and-a-half pounds (680 grams).

Steven Sinofsky, the president of Microsoft's Windows division, called the device a "tablet that's a great PC - a PC that's a great tablet".

The tablet's debut is set to coincide with the forthcoming autumn release of Microsoft's much-anticipated Windows 8 operating system. A slightly thicker version - still about half an inch (less than 14 millimetres) thick and less than 2 pounds (910 grams) - will work on Microsoft's 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 0.12 inches (3 millimetres) thick. The kickstand for both tablets was just 0.03 inches (0.7 millimetres) thick, slimmer than a credit card.

Microsoft has been making software for tablets since 2002, when it launched 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 did not 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 in 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.

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