SEATTLE _ In a significant break from a longstanding Microsoft Corp. tradition of creating services primarily for its own platforms first, the company on Thursday announced Office for iPad, its suite of productivity apps that have been optimized for touch and for use on Apple Inc.’s market-dominating tablet.

The Office for iPad apps _ specifically Word, Excel and PowerPoint apps _ went live Thursday morning in Apple’s iTunes App Store.

The apps are free if users only want to view and present documents, spreadsheets and slides.

But users who want to create and edit documents will have to have a subscription to Office 365, Microsoft’s cloud version of its market-dominating productivity suite. (“Cloud” refers to services and data that live on remote servers and can be accessed by users online.)

The Office for iPad apps come free for Office 365 subscribers.

The announcement, made at a news briefing Thursday in San Francisco, was new Microsoft CEO Satya Nadella’s first official media event since taking over last month from former CEO Steve Ballmer.

Nadella called Thursday’s announcement an example of the “magical coming-together of the cloud and mobile.”

The Office for iPad launch also marks Nadella’s first big move toward realizing his “mobile first, cloud first” vision for the company _ a vision that includes the recognition that Microsoft has to be far more open to other platforms, with services designed to run on or work seamlessly with rival companies’ operating systems and services.

Making Office available for rival Apple’s iPad marks a significant shift away from Microsoft’s practice in the past few decades of centering its offerings on Windows.

(A notable exception early on in Microsoft’s history was, ironically, Office for Mac, which Microsoft offered at a time when it was trying to expand its own user base.)

The thinking for years at Microsoft was that its products and services _ including cash cow Office _ all had to bolster and protect its core Windows franchise, which is still the dominant operating system used on PCs worldwide.

But at a time when PC sales are declining yearly and mobile devices have become pervasive, Microsoft’s presence and relevance in computing has been declining.

The overwhelming majority of the world’s smartphones and tablets run on Google’s Android or Apple’s iOS operating systems, rather than Microsoft’s Windows, Windows RT or Windows Phone platforms.

At the media briefing Thursday, Nadella said Windows is still “a massive agenda for us. We will innovate.”

At the same time, he said, “we are absolutely committed” to making the company’s applications run well cross-platform.

“It is about being able to excel everywhere our customers are,” Nadella said.

“What motivates us is to make sure that we build the great experiences that span the digital life and digital work of our customers, both individually and as organizations. And that’s what you can count on us doing, both with Windows as well as other platforms.”

Microsoft has been wrestling with the dilemma of whether to offer its marquee productivity suite on competing platforms _ thereby gaining more users and revenue for Office _ or to keep Office primarily for its own platforms, thereby protecting Windows but possibly losing scores of potential Office users who would turn to alternative productivity apps.

Some on the Office team have reportedly been working on a version of Office for iPad for years now, and Microsoft presumably could have launched such an offering years ago.

But others at Microsoft still held that a touch-optimized Office for tablets should be launched on a Microsoft device and platform first.

Launching Office on the iPad was “something that Microsoft really needed to do,” said Al Gillen, an analyst with research firm IDC. “I’m not sure it would’ve happened with Steve Ballmer at the helm.”

Microsoft’s initial response to the rapid rise of mobile was to try to extend its dominance in the PC market into the mobile market with Windows 8, an operating system that Microsoft touted as being optimized for both touch-based mobile devices and mouse-and-keyboard desktops and laptops.

Instead, many users found Windows 8 jarring, with two markedly different ways of interacting with the operating system: one the traditional desktop interface and the other a new tile-based design that worked well with touch.

That strategy into the mobile world “has not worked,” said David Cearley, an analyst with research firm Gartner.

Thursday’s announcement from Microsoft, “I view as the first major statement in the market from Satya on what his mobile-first, cloud-first agenda really means,” Cearley said.

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