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      Why do computers use binary?

      I can explain why computers use binary to represent all data and instructions.

      Lesson 1 of 6
      New
      New
      • Year 10
      • AQA

      Why do computers use binary?

      I can explain why computers use binary to represent all data and instructions.

      Lesson details

      Key learning points

      1. Computers use binary to represent all data and instructions.
      2. Binary is a number system consisting of 1s and 0s.
      3. Binary can be represented by two-state electrical signals within circuits.
      4. A transistor that is “on” represents a 1; a transistor that is “off” represents a 0.

      Keywords

      • Data - facts and figures in their raw form

      • Binary - a number system that uses the digits 0 and 1 to represent data

      • Instruction - directions on how to carry out a specific task

      • Transistor - a tiny electronic switch controlled by electricity

      Common misconception

      Computers use binary for data and instructions but they can use other number systems just as easily.

      Computers have to use binary as they are powered by electrical circuits which contain transistors which can be switched on and off using electricity. Using other number systems would require more complex circuitry.

      When getting students to think about the number of possible combinations it is useful for them to write out each possible combination in a table. This will also help when they start binary conversions later in the unit.
      Teacher tip

      Equipment

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

      6 Questions

      Q1.
      People may write a message for a number of reasons. Which of these is NOT a reason to write a message?

      to send information across a long distance
      to share knowledge
      to tell a lot of people something at the same time
      Correct answer: to forget what is in the message

      Q2.
      Written messages can appear in many forms. Put these forms of writing into date order, from oldest to most recent.

      1 - Egyptian hieroglyphs
      2 - handwriting using the alphabet
      3 - electronic writing using a computer

      Q3.
      A computer can store and instructions.

      Correct Answer: data, ata

      Q4.
      Select all the ways that a light bulb can appear.

      Correct answer: on
      Correct answer: off
      both on and off at the same time

      Q5.
      What is the next number in this sequence: 1, 2, 4, 8…?

      Correct Answer: 16, sixteen

      Q6.
      What does the word 'binary' mean?

      one
      Correct answer: two
      ten
      many

      Assessment exit quiz

      6 Questions

      Q1.
      Match the words to the correct description.

      Correct Answer:binary,a number system that uses the digits 0 and 1 to represent data

      a number system that uses the digits 0 and 1 to represent data

      Correct Answer:data,raw facts, like numbers or text, presented without context or meaning

      raw facts, like numbers or text, presented without context or meaning

      Correct Answer:instructions,directions on how to carry out a specific task

      directions on how to carry out a specific task

      Correct Answer:transistor,a small electronic switch controlled by electricity

      a small electronic switch controlled by electricity

      Q2.
      Why do computers use binary?

      Binary allows messages to be encoded so hackers can’t read them.
      It is the easiest language to program in.
      Correct answer: Electrical circuits use transistors that can be switched on and off.
      Computers only deal with numbers.

      Q3.
      What types of data can be represented by binary when stored on a computer?

      Correct answer: video
      emotion
      light
      Correct answer: sound

      Q4.
      If 1001 represents on, off, off, on, what does 01 represent?

      Correct Answer: off, on, off on

      Q5.
      Write the binary number that would represent off, on, on, off, off, on, off, on. You don’t need any spaces or punctuation.

      Correct Answer: 01100101

      Q6.
      Five binary digits allow 32 combinations, six binary digits allow 64 combinations. How many combinations can we represent with eight binary digits?

      128
      Correct answer: 256
      512
      1024

      Lesson appears in

      UnitComputing / Representation of numbers

      AQAComputing

      OCRComputing