Microsoft launched Office for iPhone and Android tablets earlier this week, bringing the productivity suite to another half a billion potential users. Word, Microsoft's most popular service in the suite, has already topped the iPhone free store.

The big surge in popularity comes the same week Microsoft announced Office would be free, to everyone on mobile. Microsoft is hoping to hook new users onto the productivity suite, getting them onto the Office 365 subscription to use the desktop tools.

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In a world where Apple offers iWork and Google offers Drive for free to customers, Microsoft trying to get mobile customers to spend $10 per month on a subscription was not working, but this could bring more users onto the suite.

It is not known what Microsoft will do to try and draw mobile-only customers into a paid agreement. Potentially, Microsoft could release the full business suite of Office on mobile - but only offer the basic tools for free to customers.

Right now, Office for mobile consists of Word, Powerpoint and Excel. For power users, desktop is still the first-class option, but for students and small-time users, this might be enough to get most of the work done.

OneDrive subscriptions could be another reason to push the free model, with the limited storage on mobile, cloud storage is becoming more necessary to save all files and folders. Users can getunlimited free OneDrive storage, if they subscribe to Office 365.

Microsoft faces tough competition staying on the top of the charts, with WhatsApp, Facebook, YouTube, Instagram and Snapchat all continuing to grow on the charts. Apple charts the top app depending on the past day/week, showing the huge amount of Word downloads in just under one day.

TagsOffice, Word, word processor, iPhone