Microsoft

an army of software developers as allies in its campaign to build enthusiasm for the new release. The company is using the three- day conference, called Build, to demonstrate more features and app- building tools, with an emphasis on mobile devices as well as PCs.

“Our goal is to make Windows 10 the most attractive development platform ever,” vice president Terry Myerson said.

To win over consumers who use competing software, Microsoft needs to persuade outside developers, who create software for consumers and corporate clients, it’s worth their time to create new apps and programs for Windows 10.

“Getting developer buyin is absolutely the crucial thing,” said J. P. Gownder, a tech industry analyst at Forrester Research. He said Microsoft has struggled with a “chicken- and- egg” problem, in which developers have been reluctant to build mobile apps for Windows because relatively few people use Windows phones and tablets.

Currently, there are more than 1.4 million apps for Android phones and about the same for Apple devices, while there are only a few hundred thousand apps that work on Windows phones and tablets.

Microsoft’s move to help developers adapt their Apple and Android apps for Windows 10 is a major change from the past, when each company maintained rigid differences in their software platforms. Microsoft is also hoping to entice developers by promising that apps for Windows 10 will work equally well on PCs, mobile gadgets, Xbox game consoles and even the HoloLens.

The company has another big carrot to wave in front of those developers: Microsoft has already said it will release Windows 10 as a free upgrade to people who now have PCs or other gadgets running the previous two versions of Windows, provided they upgrade in the coming year. That could help create a huge new audience of Windows 10 users in a relatively short time, Gownder said.

Myerson predicted there will be a billion devices using Windows 10 within the next two to three years. Apps for all those devices will be distributed through a single Windows app store. Myerson also said Microsoft will partner with wireless carriers so consumers who lack credit cards can pay for apps on their phone bill — a popular method in developing nations.

Microsoft has not said exactly when Windows 10 is coming, although some were hoping the company would announce a date Wednesday.

Since he became CEO last year, Nadella has been presiding over a major overhaul at Microsoft. He has redesigned some of