Google is known in almost every country as the world’s dominant search engine, Amazon as the world’s biggest online retailer, and Microsoft as the computer software powerhouse behind Windows.

But the three companies are also locked in a battle to define the next revolution in computing, a gold rush that could become even more lucrative than the hundred-billion dollar operations they run today: the cloud.

Cloud computing lets companies or people essentially rent on-demand processing power, storage and software over the internet. Instead of buying expensive computer servers, memory and programs, companies can now hire them, tapping into the vast enormous data centres run by the likes of Google, Amazon and Microsoft. The cloud is the difference between being able to listen only to the music you have stored on your computer and finding any song on an on-demand internet service like Spotify, and the difference between losing a crucial document and having it accessible from any computer with an online file locker.