At the end of this month, at its Professional Developers Conference, Microsoft intends to unveil something that CEO Steve Ballmer yesterday referred to as "Windows Cloud." Ballmer explained that "Just like Windows Server looked a lot like Windows but with new properties, new characteristics and new features, so will Windows Cloud look a lot like Windows Server."

Speaking at an IT event in London, Ballmer explained that Microsoft recognized the need for a new operating system designed for the cloud.

"We will introduce one in about four weeks," Ballmer said, adding:

"We’ll even have a name to give you by then. But let’s just call it for the purposes of today ‘Windows Cloud’."

Such a move by Microsoft has been long anticipated, though at this stage experts don't know whether Microsoft's plan is to release a version of Windows Server built to manage the special needs of services in the cloud, or a true all-new "Cloud OS" or what.

Over a year ago Brian Hall, general manager of Windows Live, was telling reporters that Windows Live, while not a Cloud OS as such, was certainly what he called 'Cloud-centric' - here are his exact words from July 2007:

"Cloud-centric is probably a better way to say it because Cloud OS makes it sound like it is only running on the cloud. A lot of the data, a lot of the apps, a lot of the interesting things are on the edge. They are on the PCs. They are on the Xboxes. They are on the phones."

• Amazon EC2 To Add Windows