NEW YORK - Microsoft kicked off a campaign for its newest operating system, Windows 8, and its Surface tablet computer at New York's Pier 57. Designed to run on both PCs and tablet computers, Windows 8 heralds the biggest change to the industry's dominant operating system in at least 17 years.

Windows 8 attempts to bridge the gap between personal computers and fast-growing tablets with its touch-enabled interface. It represents Microsoft's answer to the growing challenge from Apple's iPad.

The launch event came amid a slew of other tablet offerings ahead of the holidays. Apple Inc. unveiled its iPad Mini with a 7.9-inch screen on Tuesday. Amazon.com Inc. and Barnes & Noble Inc., makers of the 7-inch Kindle Fire and Nook Tablet, are coming out with larger versions next month.

Surface is Microsoft's first venture into making computer devices. The device goes on sale Friday, as will computers and other tablets running Windows 8.

Here's a running account of the Windows 8 event, presented in reverse chronological order. All times are EDT.

Presenters include Microsoft CEO Steve Ballmer; Windows chief Steven Sinofsky; Julie Larson-Green, the executive in charge of Windows Program Management; Michael Angiulo, who heads the Windows Client and Ecosystem Team; and Panos Panay, general manager of the Surface team.

___

2:25 p.m.

People in the audience were given hands-on time with the Surface after the presentation.

There were few surprises during either of the presentations. In afternoon trading, Microsoft gained 2 cents to $27.92.

___

2:15 p.m.

What is Surface, a laptop or a tablet?

"It's not just a tablet, but it's actually the best tablet I've ever used," Sinofsky said. "It's not just a laptop, but it's the best laptop I've ever used."

Sinofsky said the Surface has twice the storage memory as competitors for the same price — though he didn't mention that about half of it gets taken up by the operating system and pre-loaded software.

The Surface event wrapped after about 40 minutes.

___

2:10 p.m.

There's a keyboard cover for Surface, costing $100 extra for the basic, $499 device. There are "keys" on the cover that allow for typing. Panay noted that the cover is pressure-sensing, so if you just rest your hands on it, it's not going to start erratically typing.

The cover also folds back and can act as a support for the device's kickstand if you're placing it on your lap.

___

2:05 p.m.

As previously disclosed, the Surface will come with the Office software suite for word processing, spreadsheets and other business tasks. Other tablets running Windows RT, the lightweight version of the operating system, will also come with a version of Office for free.

___

2 p.m.

The Surface has a kickstand. The back camera is angled in such a way that when it's leaning on the stand, it shoots straight out, not toward the table.

___

1:55 p.m.

In a gimmick to show its durability, Microsoft showed a picture of Sinofsky standing on a Surface outfitted with wheels to make a skateboard. The company also showed three skateboard Surfaces on stage.

___

1:45 p.m.

Microsoft described Surface as an extension of Windows, though the company noted that it's about extending other Microsoft products, too. Panay demonstrated watching movies and listening to music on the Surface and used an Xbox to relay content.

___

1:35 p.m.

Microsoft began a launch event for the Surface tablet at the same location at Pier 57.

___

1:10 p.m.

One thing missing from Thursday's launch event: partners, such as PC makers, on stage.

With the launch of Surface, Microsoft is competing with some of its partners. One analyst suggested that PC makers didn't want to come because of that, as going alone in a presentation was unusual.

"Maybe it's a freeze-out because of the Surface," said Richard Doherty, CEO of technology assessment and market research company Envisioneering.

Larson-Green said there was no such tension. She said PC makers gave Microsoft devices to show on stage, and representatives from each of them were in the audience.

"We made it a Microsoft event to keep it short," Larson-Green said.

The event clocked in at less than an hour. By contrast, Apple's event Tuesday went about 75 minutes — and that was short for the company. That event didn't have any partners either, though past events from Apple have had them.

___

12:45 p.m.

Included with Windows 8 is a new version of Microsoft's browser, Internet Explorer 10. Microsoft says it's "perfect for touch" and will be designed to work seamlessly with its Internet-based storage service, SkyDrive. It's similar to how the latest version of Apple's Safari browser on Mac computers works with its iCloud storage service. In the case of Apple, Web pages open on other machines logged in with the same account can be easily accessed.

___

12:30 p.m.

One of the biggest changes with Windows 8 is the disappearance of the familiar start button at the lower left corner of the screen. It has been used to pull up a menu of applications and settings, and to shut down or restart the computer. Instead, people will have to swipe the edges of the screen.

There will be a new screen filled with a colorful array of tiles, each leading to a different application, task or collection of files.

Reached off stage, Ballmer was asked by The Associated Press whether there was any chance of bringing back the start button.

"You've got a whole screen as a start button," he said, referring to the screen of tiles.

At least one PC maker is restoring the start button in an effort to minimize the potential frustration caused by Windows 8's new look. Samsung Electronics Co. has announced models in which it built its own, optional start button that could be used to pull up a menu of applications.

During the presentation, a Microsoft executive had noted that the start button was something people had to get used to when it was first introduced, suggesting that people will get used to the new tile format, too.

___

12:20 p.m.

The keynote has ended, although the launch event continues. Microsoft plans to return at 1:30 p.m. with a presentation on Surface.

___

12:15 p.m.

Ballmer said outside developers have been working "fast and furiously" to make apps for Windows. He said developers have praised how they can write the same app for a variety of devices — desktops, laptops and tablets.

"Windows 8 PCs really are the best PCs ever," he concluded.

He encouraged people to visit a store to try Windows 8 themselves.

"Seeing, touching, clicking and swiping really is believing," he said.

___

12:10 p.m.

Ballmer talked about the phone version of Windows, known as Windows Phone 8. There's an event planned Monday.

"I can't wait to show you how we've really reinvented the smartphone around you," he said.

___

12:05 p.m.

In telling people that their relationship with machines will change, Ballmer said, "Picture your start screen filled with everyone and everybody who's most important to you."

He added, "Windows 8 will help you do everything and will make it a lot of fun, frankly, to do ... nothing."

He said people will have several devices to choose from, including new designs that combine the best of PCs and tablets.

Ballmer said Windows 8 will also have a range of tools, including built-in search, news, finance, sports and other apps powered by Bing, Microsoft's search engine.

Bing has been struggling to compete with Google's search engine. Having it prominent in Windows 8 could help boost traffic to it.

___

Noon

Ballmer appeared on stage.

"Windows 8 shatters perceptions of what a PC now really is," he said. "We've truly reimagined Windows and kicked off a new era of Microsoft and for our customers."

___

11:55 a.m.

Microsoft showed off five devices running Windows RT, a lightweight version of Windows 8. Unlike the full version, RT can run only apps developed for it and obtained from the Windows online store.

One of them was the Surface. Other machines shown included ones from Dell Inc., Samsung Electronics Co. and AsusTek Computer Inc.

___

11:50 a.m.

The event was being held in a cavernous former bus depot, with more than 500 people in the audience. Pier 57 is located on the Hudson River, near the city's Meatpacking District.

___

11:45 a.m.

There have been few surprises, as Microsoft announced the release date and made preview versions available long ago. Microsoft's stock climbed 3 cents to $27.93 in midday trading. Trading volume was low, less than half of the average.

___

11:40 a.m

Larson-Green and Angiulo appeared on stage to demonstrate a Windows 8 machine upgraded with Windows 7 devices.

___

11:35 a.m.

Microsoft announced the grand opening of its Windows online store, modeled after Apple's iTunes store. It will sell apps and content for Windows machines.

The store will be open in 231 markets around the world. (Companies typically restrict sales to specific markets, as some content may not be available worldwide because of copyright issues and local laws. A launch in that many markets at once is unusual.)

There are plenty of third-party apps available for iPads, iPhones and devices running Google's Android system. Sinofsky acknowledged that Microsoft's app store will likely be slim at first.

"We know some people might count apps and look for their favorite apps," he said. Hinting at more to come, he added, "We see today as a grand opening."

He said there are hundreds of apps added every day, in 109 languages. He said the Windows store has more apps than any other app store had at its opening.

___

11:30 a.m.

Sinofsky said there have been 1,000 PCs certified for Windows 8, with the cheapest costing about $300. There will also be new models of slim, lightweight laptops called ultrabooks.

He reiterated that Windows 8 is designed to work equally well with touch-screen computers and those using keyboard and mouse commands.

___

11:25 a.m.

Sinofsky opened by talking about past versions of Windows. He noted that the current version, Windows 7, came out three years ago this week. He said 670 million Windows 7 licenses have been sold since then.

He said that in creating Windows 8, "We shunned the incremental. We boldly reimagined Windows." He said there have been 16 million installations of preview versions of Windows 8.

The software will go on sale at midnight local time around the world.

___

11:20 a.m.

Sinofsky appears on stage, which is flanked by 21 Windows 8 devices, ranging from tablet computers to "all-in-one" PCs, which are desktop computers with a built-in screen.

"Windows 8 is a major milestone in the evolution and revolution of computing," Sinofsky declares.