Binary numbers: how a computer counts with bulbs
Four bulbs are worth 8, 4, 2 and 1. Switch them on and off to make numbers, and find out how a computer stores every number with just ones and zeros.
Core concept
A computer stores numbers as bits that are either on (1) or off (0); each bit is worth twice the one to its right, and the number is the sum of the bits that are on
Topic: Digital concepts
Inside a computer, everything is stored as tiny switches that can only be on or off. We write on as 1 and off as 0, and each switch is called a bit (a binary digit). With only two digits, a computer counts in the binary system. In our everyday numbers each place is worth ten times the one to its right (ones, tens, hundreds). In binary each place is worth twice the one to its right: 1, 2, 4, 8 and so on. In this lab four bulbs stand for four bits, worth 8, 4, 2 and 1. The number they show is the sum of the bulbs that are on. So 0101 (the 4 and the 1 on) is 5.
What you will learn
- Explain that a bit is a switch that is either on (1) or off (0).
- Write numbers from 0 to 15 in binary using four bits.
- Turn a binary number into an ordinary number by adding the place values.
- Explain why 4 bits can show 16 different numbers.
Before you start
- Add small whole numbers and know place value (ones, tens, hundreds).
Materials
- Four torches or four cards with a 1 on one side and a 0 on the other
Equipment
- None needed: this lab can be done with your hands (fingers up for 1, down for 0)
Procedure
- Switch on bulbs to show the number 5, and record.
- Show the number 9, and record.
- Show the biggest number four bulbs can make, and record.
- Show the number 10, and record.
How this simulation is simplified
- Each bulb is one bit: on is 1 and off is 0.