Error Detection

The world is noisy place, and errors can occur whenever information is stored or transmitted. Error detection techniques add extra parity bits to data to determine when errors have occurred.

This activity is a magic trick which most audiences find intriguing. In the trick the demonstrator is “magically” able to figure which one out of dozens of cards has been turned over, using the same methods that computers use to figure out if an error has occurred in data storage.


Activity description (PDF)

Translations and other versions:



  • The parity tiles on a magnetic blackboard, from a demonstration in Japan.

Related Resources

  • An older version of this activity can be downloaded in PDF format here. The content is similar to the current version, but there’s some extra technical information.

 Curriculum Links

Great Principles of Computer Science [info]

Communication, Recollection

ACM K12 Curriculum [info]
  • Level I (Grades K–2) Topic 11: Understand how 0s and 1s can be used to represent information, such as digital images and numbers.
New Zealand Curriculum [info]
    • Mathematics Level 1: Equations and expressions
      • Communicate and explain counting, grouping, and equal-sharing strategies, using words, numbers, and pictures.
    • Mathematics Level 1: Number strategies
        • Use a range of counting, grouping, and equal-sharing strategies with whole numbers and fractions.
        • Understand that technological outcomes are products or systems developed by people and have a physical nature and a functional nature.
      • Understand that technology is purposeful intervention through design.
  • Technology Level 3: Technological systems
    • Understand that technological systems are represented by symbolic language tools and understand the role played by the “black box” in technological systems.