Cloud-computing giants take in billions running software code

San Francisco

IMAGINE building an enormous beach resort, maybe the best in the world. Instead of renting the rooms, you charge guests based on the grains of sand they touch. You charge very little per grain, but if they lie on enough of them, it adds up.

That is one way to think about what is going on at the world's biggest cloud-computing companies. Instead of grains of sand, think about computing cycles, the activity that goes on in a computer server that is running software. For a price, think about one line of software code for two one-millionths of a penny.