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Grade 7 · unit review

Review: Represent, Compress and Protect Information

Decode 3A2B. Compare keeping that record, sorting its expanded text and keeping only the A count. Explain why a public character code is not a security guarantee.

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Unit review questions
1. Classroom encoding stores 12 characters at exactly 2 bytes each. Storage excluding all overhead?
Need a hint?
  • Multiply the supplied character count by the stated bytes per character.
  • Character count and byte count need not be equal.
2. Record 2A2B1A. Decode the stated run-length record.
Need a hint?
  • Use the explicit input, condition and question aspect.
  • Reject a choice that adds an unsupported condition or answers a different question.
3. Only the maximum value of a list is saved. No other values or positions are recorded. Which complete reconstruction claim is supported?
Need a hint?
  • Use the explicit input, condition and question aspect.
  • Reject a choice that adds an unsupported condition or answers a different question.
4. Someone claims a simple substitution table known to every reader keeps a message secret from those readers. Which kind of statement is this?
Need a hint?
  • Distinguish a representation convention from a confidentiality protection using a secret key.
  • A hidden-looking code is not evidence of a secure cryptographic scheme.

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Decode 3A2B. Compare keeping that record, sorting its expanded text and keeping only the A count. Explain why a public character code is not a security guarantee.

Work on paper or in your own document. Explain the choices you made.

  • Use only supplied fictional inputs and state the relevant rule.
  • Include labeled steps or evidence for each decision.
  • Name one limitation or tempting mistake.
  • Check that the result meets the task and revise a justified error.
Compare with a model response

3A2B restores AAABB exactly. Sorting this particular sequence happens to preserve its shown order, but a sort is not reversible for arbitrary input; a count alone loses sequence details. A public character code changes representation, not secret access.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.