How binary digits work

Steps

1. Ask: how does a digital device store information? Write down every answer, then come back to them at the end.
2. Four children stand in a line and hold the cards 8, 4, 2, 1 from left to right, with the dots hidden at first.
3. Reveal the pattern: each card has twice as many dots as the one to its right.
4. A card is either shown (on, 1) or hidden (off, 0). Call out a number and let the line show the right cards. Add the dots to check.
5. Count from 0 to 15 by changing as few cards as possible each time. Write the pattern of ones and zeros on the board.
6. Add a fifth card. What is the biggest number now?

Talk about it

• What is the biggest number with four cards? With five?
• Why does a computer use on and off?
• Which card changes most often when counting?