Microsoft began its Windows Phone 7.5 "Mango" update to smartphones globally late on Tuesday.

The update of the mobile operating system is expected to roll out gradually, lasting less than four weeks, claimed Eric Hautala, general manager of customer experience engineering wrote in the Windows Phone blog.

Windows Phone 7 customers will learn of the update's availability with a message that pops up on the phone. Users will need to connect the phone to a computer with the latest version of Zune Software for PC or WindowsPhone 7 Connector for Mac, Hautala said.

Microsoft also said users can prepare in advance by making room for the update's data on their phones, by removing unwanted apps. They also need to make sure the phone is fully charged. Users also need to free up space on the computer for a backup copy of existing phone software.

Hautala said Microsoft is making the rollout of 7.5 in a "simultaneous, coordinated, global update that cuts across carriers, phone models and countries," in an apparent response to concerns raised about earlier update delays and glitches. "This time, almost everybody is going first," he said, and listed a website called "Where's my phone update?" where users can check on the status of the update for their phones.

Hautala said Microsoft won't "just blast out" to all users at once because the update is complex with a new operating system as well as new software supplied by various handset makers. "It essentially means that we're not supplying just one update, but many different ones, given the variety of Windows Phones and carriers out there to choose from," he said.

He said this week the update will go to 10% of customers, then later to 25% more, adding more later. "If we hit unexpected snags, we might have to temporarily slow or halt the update rollout," he noted.

The hundreds of improvements expected on Mango have been widely reported. Among them is that Mango will run a full desktop version of the Internet Explorer 9 browser, not just a mobile variation. The OS will also include Office apps, Skype and Xbox Live gaming capabilities.

Microsoft, on its website, called Mango "people-centric." That generally means the update offers multitasking and integrated social networking "for connecting with the people in our lives," Microsoft said.