Microsoft's Windows 8 update, code-named Windows Blue, will be formally released as Windows 8.1 and will be free for customers who have the new OS installed.

Windows 8.1 will be an "update" for both Windows 8 and for Windows RT, the version of the OS designed for devices that run on ARM chips, said Tami Reller, the chief financial officer and chief marketing officer of the Windows Division, speaking at the JP Morgan Technology, Media & Telecom Conference Tuesday.

As an update, Windows 8.1 will be more substantial than the regular patches Microsoft pushes out for the OS, but will not represent a dramatic leap like the upgrade from Windows 7 to Windows 8, she said.

Moreover, Windows 8.1 will be "really easy" and "straightforward" for customers to install, Reller added.

Microsoft's decision confirms speculation from industry analysts who spoke recently about this topic.

Last week, Reller and the other Windows chief, Julie Larson-Green, a corporate vice president in charge of the OS' development, provided more details about Windows Blue, including that it will be delivered before the end of the year and that a preview will be released at the end of June during Microsoft's Build conference for developers.

Larson-Green didn't say what changes Windows Blue will feature, but conceded that Microsoft has discussed user complaints about the removal of the start menu on Windows 8 and that it might be useful to restore it.

Asked if she could be more specific about the final release of Windows 8.1, Reller on Tuesday declined to provide a more concrete date but acknowledged that Microsoft wants to give OEM partners a chance to load it into computers they release for the holiday season.

She also reiterated that OEM partners are working on smaller Windows 8 and Windows RT tablets with 7-inch and 8-inch screens, and disclosed that there are now more than 70,000 applications for the OS in the Windows Store.

She also said Microsoft is satisfied with the amount and variety of Windows 8 and Windows RT devices, including desktop PCs, low-priced laptops with touch screens, sophisticated convertible laptops with detachable keyboards that double as tablets, all-in-one PCs and other variations.

"We feel very good about the direction we're headed with Windows 8," Reller said.

Windows 8 has a drastically redesigned interface based on tile icons intended to make the OS optimized for touchscreen devices such as tablets. However, it has not been an unqualified success and the lack of uptake by users has been blamed in part for the dismal performance of the PC market overall.

The Windows 8.1 preview version that will be delivered in June will be available for anyone to download and test drive, not just developers.

Juan Carlos Perez covers enterprise communication/collaboration suites, operating systems, browsers and general technology breaking news for The IDG News Service. Follow Juan on Twitter at @JuanCPerezIDG.