The bit
- Bit is short for binary digit. Binary means 'made of two'.
- One bit = one switch = one yes/no answer.
- One bit alone can only say 2 things: 0 or 1.
Signals as bits: why computers use binary
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What this lesson covers
Topic 2 Bits and bytes
KS3 Computing · A bit is one switch: 0 or 1. A byte is 8 bits. Every photo, song and game is measured by counting these.
Computer SystemsCambridge Lower Secondary Computing 0860
You will learn to
- Explain why computers use only two states: on and off.
- Work out how many patterns 1 to 8 bits can make, by doubling each time.
- Show any number from 0 to 255 using eight bit cards (128, 64, 32, 16, 8, 4, 2, 1).
Success criteria
- I can say that a bit is one 0 or 1, and a byte is 8 bits.
- I can show 5 and 200 with the bit cards.
- I can explain why 8 bits stop at 255.
Key words
Say each word, then read what it means. Every one is in the glossary too.
- Bit
- One binary digit, 0 or 1. One switch.
- Byte
- 8 bits. 256 possible patterns.
- Nibble
- 4 bits. One hex digit.
The explanation
Read it here, or open the study page below to go one step at a time with things to try.
More bits = more patterns
| Bits | Every pattern | How many |
|---|---|---|
| 1 | 0, 1 | 2 |
| 2 | 00, 01, 10, 11 | 4 |
| 3 | 000, 001, 010, 011, 100, 101, 110, 111 | 8 |
| 4 | 0000 … 1111 | 16 |
| 8 | 00000000 … 11111111 | 256 |
?Why?
Why does it double each time?
Take all the patterns you had. Put a 0 in front of each. Then put a 1 in front of each. Same list, twice.
Bits vs bytes in internet speeds
!Watch out
File sizes use bytes (big B: MB). Internet speeds use bits per second (small b: Mbps). A 100 Mbps connection gives at most 100 ÷ 8 = 12.5 MB per second.
Study it
Open the study page and go one step at a time.
Topic 2 · Year 7
Bits and bytes
A bit is one switch: 0 or 1. A byte is 8 bits. Every file is measured by counting these.
Topic 1 · Year 7What a computer is
A computer takes information in, follows instructions to change it, and gives a result out. It does all of this with billions of tiny on/off switches.
The steps for this lesson
- Topic 2, step 2: More bits, more patterns (How many patterns?)
- Topic 1, step 4: Naming the states: 0 and 1 (Flip a switch)
- Topic 2, step 3: The biggest number (The biggest number n bits can hold)
Try it
Check yourself
One question at a time. The reason shows after each answer.
Saved on this device.