Algorithm = exact steps, in order

You tell a friend the way to your house. You say exact steps, in order.

That list of steps is an algorithm.

An algorithm is an exact list of steps, in order.

Order matters

Socks, then shoes: easy. Shoes, then socks: it fails.

A grid is rows and columns of squares. A move past its edge does nothing. Start at the top-left corner.

1. Up, down, right. "Up" has no square above, so nothing happens. "Down" moves one down. "Right" moves one right. You end one down and one right.
2. Down, up, right. "Down" moves one down. "Up" moves back to the top. "Right" moves one right. You end one right.

Same steps. A different order gives a different place.

Try the lab to finish this lesson.