While tech giant Microsoft is expected to introduce Windows 9 in a Tuesday event in San Francisco, California, rumors are already circulating on what to expect from the latest operating system.

There's also speculation Microsoft will offer free upgrades of the OS to users with Windows 8 on their computers.

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Publicized by tech news site BGR on Saturday, the rumor was initially spotted by Indonesian tech site Detik earlier in the week. Previously, Andreas Diantoro, Microsoft Indonesia's president, was caught saying the "Windows 9 upgrade will be available free of charge to all existing Windows 8 users once it's released."

Although the story by Detik is in Indonesian, BGR got hold of a translation saying that once Threshold (a codename for Windows 9) is released, users with the latest OS "will be able to easily install the Windows 9 update after downloading it from Microsoft."

The story saying the Redmond-based company was planning to release Threshold as an upgrade has been around for some time. Other rumors reported that legacy Windows XP users will also be given free upgrades.

BGR noted that if any of the rumors are proven true, it's unclear what would happen to users with other Windows operating systems such as Windows 7 and Vista.

Meanwhile, another set of Threshold rumors emerged a few weeks earlier courtesy of WinFuture, a German tech news site.

Screenshots and videos of the alleged Threshold build suggest Microsoft is currently working on several modifications of the Live Tile interface from Windows 8

Windows 9, which is expected to be released next year, will see the comeback of the Start menu. It will also have a multi-desktop feature, a Notification Center and include the Cortana digital assistant.

Tagswindows 9, Windows 9 reveals on Sept. 30, windows threshold, Threshold, OS Threshold, Codename Threshold, Microsoft Indonesia, Windows 8, windows vista, Windows XP, Cortana