In a bid to catch up with Apple and Google in the mobile devices space, Microsoft has come up with updated Windows Phone software, which will be offered to smartphones and tablet makers free of charge.

The Redmond-based software giant unveiled the updated version of Windows Phone software during a recently held event at its Build developers' conference in San Francisco; and announced that it would be available free for manufacturers of smartphones and tablets with screens of less than nine inches.

Previoulsy, the company charged smartphones and tablet manufacturers a licensing fee of $5-15 per device.

The updated Windows Phone 8.1 OS for mobile devices now includes an Apple Siri-like voice-controlled digital assistant, dubbed Cortana. It also reinstates the widely popular Start menu for laptops, larger tablets and desktop PCs. The Start menu was axed in Windows 8.

Commenting on the updated Windows Phone software, FBR Capital Markets' Daniel Ives said, "Microsoft is facing challenges on the mobile and tablet fronts and need to change their strategy to move the growth needle, this is a good and logical first step."

Satya Nadella, who was appointed as CEO of the world's biggest software maker in February, is preparing the company for an era where mobile devices have become central. Existing Windows Phone 8 users will get the new Windows Phone 8.1 software over the next few months.