Google is work­ing on an operating system for inexpensive net­book computers that are becoming popular among consumers primarily interested in surfing the web.

That is a direct challenge to Microsoft, whose next operating system, Windows 7, is being geared for netbooks as well.

Google’s new system will be based on the nine-month-old web browser, Chrome. Google intends to rely on help from the community of open-source programmers to develop the Chrome operating system, which is expected to begin running computers in the second half of 2010.