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Context-Free Languages: BNF and Syntax Diagrams

AQA 75174.4.3.1A-levelLesson packSubscription
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  • 45 marks
  • about 55 minutes
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About this resource

AQA A-level Computer Science (7517) Paper 1, 4.4.3.1 Context-free languages — checking language syntax against Backus-Naur Form (BNF) or syntax (railroad) diagrams, formulating simple production rules, and explaining why BNF can represent recursive/nested languages that regular expressions and FS…

27 slides.

Lesson outline

  1. Do Now — Retrieval: Finite State Machines
  2. I-Do: What Is BNF and Why Do We Need It?
  3. Quick Check — The ::= Operator
  4. I-Do: BNF Notation, Precisely
  5. Quick Check — Terminal or Non-Terminal?
  6. We-Do: Recursion in a Production Rule
  7. Hinge Check — Which Alternative Is the Base Case?
  8. I-Do: Checking a String — Derivation Tree for "352"
  9. We-Do — Check Your Understanding: Deriving "84"
  10. I-Do: Checking Validity Against a Grammar
  11. Hinge Check — Misconception: Is a Single Letter Enough?
  12. We-Do — Check Your Understanding: Validity Checks
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