SAN FRANCISCO — Microsoft is using a three-day conference this week to give people a peek into Windows 8.1, a free update that promises to address some of the gripes people have with the latest version of the company's flagship operating system. A preview version of Windows 8.1 was released Wednesday at the start of the Build conference for Microsoft partners and other technology developers.

Although many of the new features have been shown off already, the conference offers the company a chance to explain some of the reasoning behind the update and sell developers on Microsoft's ambitions to regain relevance lost to Apple's iPad and various devices running Google's Android software.

Windows 8, which was released Oct. 26, was meant to be Microsoft's answer to changing customer behaviors and the rise of tablet computers. The operating system emphasizes touch controls over the mouse and the keyboard, which had been the main way people have interacted with their personal computers since the 1980s. But some people have been put off by the radical makeover. Research firm IDC blamed Windows 8 for accelerating a decline in PC shipments worldwide.

Microsoft's event is taking place at The Moscone Center in San Francisco. The keynote kicked off shortly after 9 a.m. PDT.

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

Presenters include CEO Steve Ballmer; Julie Larson-Green, corporate vice president for Windows; and Antoine Leblond, corporate vice president for Windows Web Services; and Gurdeep Singh Pall, corporate vice president for Bing.

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10:50 a.m.

The keynote ends after nearly two hours, without Microsoft unveiling a smaller version of its Surface tablet computer, as many people had speculated.

Microsoft's stock increased nearly 2 percent in afternoon trading Wednesday, but much of the increase came before the keynote began.

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10:45 a.m.

Microsoft executives demonstrate Project Spark, a simulator unveiled at the E3 video game conference in Los Angeles this month. It invites gamers to craft virtual worlds with the swipe of a finger, and then play through them on the Xbox One.

Ballmer uses that as an example of what a new world of apps can look like — whether it's productivity in the office or hard-core fun with gaming. He says Microsoft is trying to facilitate all that by releasing updates rapidly.

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10:30 a.m.

Microsoft unveils new capabilities with its Bing search technology, including better maps. The Windows 8.1 maps app will come with 3-D imagery, which developers can embed in their own apps.

Ask a question, and the service knows the context. For instance, when viewing a 3-D image of a building, you can simply ask, "Who is the architect?" Bing will know you are looking for the architect for that building.

Scan a business card with a camera, and optical-character recognition software can read it and have contact information translated from Spanish into English.

Pall says, "Apps are going to have eyes. They're going to have ears. They're going to have a mouth."

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10:15 a.m.

Microsoft shows off several devices from Lenovo, Acer, Samsung and others. Some cost less than $400. Microsoft praises the ability to bring touch controls to devices at various price points. Microsoft also shows off its own Surface Pro tablet and says all developers at the conference will get one.

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10:10 a.m.

Windows 8.1 will update apps automatically, and the Bing search engine will recommend new ones for you based on what you've used before.

Windows 8.1 also supports 3-D printing. On stage, Leblond starts printing a vase using a MakerBot device.

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9:50 a.m.

As previously announced, Windows 8.1 offers more ability to run multiple apps at once. With Windows 8, you can have two — one taking two-thirds of the screen, and the other the remaining third. The update no longer constrains you to that split, restoring functionality available with past versions of Windows. You're also no longer constrained to just two apps.

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9:45 a.m.

Larson-Green says Windows 8.1 revamps search so that it's not just a list of links, but all the things you can do. Search for a band, and you get that band's music along with cover art and links to its website. You can hear a snippet through Xbox Music if you don't already own that song.

Windows 8.1 also has picture editing built in and the ability to do a video chat over Skype from the lock screen. You can also see a slideshow of your photos from that screen. She says Microsoft is making all programs much easier to get to.

There's also a hands-free mode, which can be useful while cooking. Instead of touching the device with messy hands, Microsoft says, you simply wave your hand over the camera to flip through a recipe.

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9:35 a.m.

Larson-Green demonstrates Windows 8.1 on stage. She says having an update just eight months after Windows 8's launch shows how responsive the company's engineering team has become. The update, she says, "refines the vision of Windows 8."

There's a new start screen for smaller devices such as Acer's 8.1-inch tablet. An on-screen keyboard pops up from the bottom, with gesture controls added. Suggestions come up as you type; to choose one, you can slide a figure across the space bar and tap. Another gesture lets you more easily enter numbers by sliding your finger.

The email app has a new sweep command to delete all but the latest newsletter, for instance.

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9:25 a.m.

One of the shortcomings of Windows tablets is a lack of apps for them. Ballmer says that's changing. He says Facebook, for instance, is now making an app for Windows 8. There are also fantasy football apps coming from the NFL.

The crowd cheered as Ballmer mentions some of the previously announced features coming to Windows 8.1.

That includes the ability to have machines automatically start up in the older, desktop mode rather than a tablet-style, full-page start screen that Microsoft has been pushing with Windows 8. Windows 8.1 will also restore a Start button on the lower left corner of the screen, although it will work differently in bringing people to the full-page start screen rather than the Start menu found in previous versions of Windows. He also talks about new search functions, using Microsoft's Bing search technology.

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9:15 a.m.

Ballmer announces new phones from Nokia running a phone version of Windows software.

He also talks about a smaller Windows tablet than the ones previously available with Windows 8. The new Acer Iconia has a screen that measures 8.1 inches diagonally. He says Microsoft and its partners had to do a lot of work to "bring the small tablet form factor to life." Ballmer says customers should expect many smaller Windows tablets to come. That will allow Windows to compete with popular small tablets such as Apple's iPad Mini and Google's Nexus 7.