Binary Numbers
Computers use 1s and 0s because switches have two states.
About this topic
Binary is a base-2 number system that uses only the digits 0 and 1. Computers use it because electronic circuits easily represent two states, on and off, high and low voltage. Each binary digit is called a bit, and eight bits make a byte.
Just like decimal uses powers of 10, binary uses powers of 2. Place values from the right are 1, 2, 4, 8, 16, 32, 64, 128 and so on. The binary number 1011 means 1 times 8 plus 0 times 4 plus 1 times 2 plus 1 times 1, which is 11 in decimal. With n bits you can represent 2 to the power n different values, so one byte holds 256 values from 0 to 255.
Everything stored in a computer, including numbers, text, pictures and sound, is eventually reduced to bits. For example, the letter A is stored as 01000001. A common misconception is that binary is difficult; it is just counting with two symbols, so after 1 comes 10, as after 9 in decimal comes 10 with a different meaning. Learn the powers of two by heart, since they help with memory sizes and conversions.
Key ideas
- Each bit doubles in value
- 8 bits = 1 byte
- Count 0, 1, 10, 11, 100…
Quick check
Use cases: where Binary Numbers helps
- Homework: review the key idea behind Binary Numbers before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Binary Numbers without notes.
- Visual learning: play with the interactive lab to see how Binary Numbers changes when you adjust its inputs.
- Teaching a friend: explain Binary Numbers in your own words, then compare your version with the key ideas.
Computing ideas run phones, search engines, games and the wider internet.
Frequently asked questions
What is Binary Numbers?
Computers use 1s and 0s because switches have two states.
What will I learn in Binary Numbers?
Each bit doubles in value. 8 bits = 1 byte. Count 0, 1, 10, 11, 100….
Is Binary Numbers part of Computer Science?
Yes. It is one of 80 Computer Science topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Binary Numbers lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Binary Numbers?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.