Microsoft has confirmed that there will be no further public beta versions of Windows 7, and that it is now preparing the Release Candidate (RC) build.

However, the company has yet to give an exact date for the operating system's final release, other than sometime in the second half of 2009.

The disclosure came in an end of January update to the Engineering Windows 7 blog by Steven Sinofsky, Microsoft's senior vice president for Windows.

Sinofsky wrote that the next milestone for the development of Windows 7 will be the RC, to be followed by the release to manufacturing of the final code and then general availability in retail and on new PCs.

The beta of Windows 7 was made available on 8 January following an earlier pre-beta distributed at Microsoft's Professional Developer Conference (PDC) in October 2008.

The move means that Windows 7 will have had only one official beta before the full version ships, in contrast to recent versions of Microsoft products such as Windows Vista. This is because the company has taken a different approach to development with the new platform, according to Sinofsky.

"The pre-beta from the PDC was a release where we said it was substantially API complete and, even for the areas that were not in the release, we detailed the APIs and experience in the sessions at the PDC," he said.

"At that time we announced that the beta test in early 2009 would be both API and feature complete, widely available, and would be the only beta test."

Because the beta is feature-complete, the work leading up to the RC version will largely involve fixing bugs and addressing any major issues identified by testers.

"A very significant portion of our effort from beta to RC is focused exclusively on quality and performance," Sinofsky said.

"We want to fix bugs experienced by customers in real usage, as well as our broad base of test suites and automation. The path to RC is all about getting the product to a known and shippable state from an internal and external (beta usage and partner ecosystem readiness) standpoint."

Microsoft has so far declined to give a date for Windows 7's final availability, but the fact that the company is already working on an RC could indicate a sooner rather than later release.

The beta release is due to expire on 1 August, for example, and Sinofsky said that he has already had feedback from testers stating that they do not wish to revert to an older version of Windows when this deadline passes.