Monday

A neighbor brings in a tablet that crawls. Rocket swipes through the open apps. "Twelve games and three videos!" he says. "No wonder it is tired."

Raven watches the screen stutter. "What do you notice?" she asks. "It is not stopped. It is just slow."

Nova glows a steady amber. "Inside, one part does all the thinking," she says. "It takes one small step at a time. Would you like a hint? Count how many lists it is reading."

The processor is the part of a computer that follows instructions. Every app is a long list of instructions.

An instruction is one small step. Add two numbers. Compare two numbers. Move a number from one place to another. Draw one dot on the screen.

The processor reads one instruction, does it, and moves to the next. It never skips ahead and never does two at once.

A big job like showing a video is millions of tiny steps. The processor does them one after another, very fast.

A processor can only follow one list at a time. When many apps are open, it takes turns.

It does a few steps for one app, then a few for the next. It switches so fast that everything looks like it is happening at once.

With too many lists, each app gets a smaller turn. That is why the tablet in the story crawled.

Closing apps you are not using is a fix a kid may do. Fewer lists means longer turns for the apps you want.

Great thinking, Crew Technician! You know how a processor works through a list. Tomorrow you will find out just how fast it goes.