Google's new OS to take on Microsoft "the open-source software, called Chrome OS, would be available in the second half of next year. "

NEW YORK: In a direct challenge to Microsoft, Google announced late on Tuesday that it is developing an operating system for PCs based on its Chrome Web browser.

The move sharpens the already intense competition between Google and Microsoft, whose Windows operating system controls the basic functions of the vast majority of personal computers.

In a post on its company blog, Google said the operating system would initially be aimed at netbooks, the compact, low-cost computers that have turned the PC world on its head. It said the open-source software, called Chrome OS, would be available in the second half of next year.

“Speed, simplicity and security are the key aspects of Google Chrome OS,” the blog post said. “We’re designing the OS to be fast and lightweight, to start up and get you onto the Web in a few seconds.”

Google has already developed an operating system for mobile phones, called Android. And several manufacturers of netbooks are also using that software.

Google has long promoted a vision of computing in which applications delivered over the Web play an increasingly central role, replacing software that runs on the desktop. In that world, applications

run directly inside an Internet browser, rather than atop an operating system, the traditional software that controls most of the operations of a PC.