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Structuring Your Responses

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선생님을 위해: Structuring Your Responses(Computer Science, CIE)을(를) 위한 바로 쓸 수 있는 수업 슬라이드, 복습 노트 — 수업에 사용하거나, 학생들이 실시간 게임으로 즐기는 인터랙티브 클래스 활동으로 진행하세요.

수업 노트

General Approach to Programming Questions

  • Programming questions appear in both Paper 1 (algorithm understanding) and Paper 2 (design, write, test, refine).
  • Paper 2 includes a fixed 15-mark programming question at the end.
  • Answers must be in CIE pseudocode, Structured English, or a high-level language.
  • Before writing a program, ask five key questions: inputs, outputs, processes, constructs, subprograms.

Five Key Questions for Programming

  • What are the inputs? – Identify data the program receives (e.g., user input, file).
  • What are the outputs? – Determine what the program displays or saves.
  • What processes take place? – Describe the transformations or calculations.
  • What constructs will I need? – Choose sequence, selection (IF), iteration (WHILE, FOR), assignment, string operations.
  • Do I need to use subprograms? – Use built-in functions (e.g., SUBSTRING, LCASE) or user-defined procedures/functions.

Example: String Manipulation Question

  • Question: store a string, extract a substring, output lowercase.
  • Use SUBSTRING(Quote, Start, Number) – returns Number chars from position Start (1-indexed).
  • Use LCASE(Quote) to convert to lowercase.
  • Answer: assign Quote, set Start=25, Number=8, OUTPUT SUBSTRING, OUTPUT LCASE.

What is a Trace Table?

  • A trace table tracks variable values as a program runs line by line.
  • Tests ability to simulate code and record outputs accurately.
  • Typically worth 3–6 marks, often involving iteration, selection, and arrays/lists.
  • The table structure is usually provided; you fill in missing values.

Command Words for Trace Table Questions

  • Complete – Fill in the table with correct values.
  • State – Give a single value/output/result.
  • Explain – Say why something happens or changes.
  • Identify – Spot where something goes wrong or doesn't match expectations.

Steps to Tackle a Trace Table

  • 1. Read the code carefully – Understand loops, IF statements, variable changes.
  • 2. Use the trace table provided – Headings and row count guide iterations.
  • 3. Work line by line – Simulate in head/paper, update each variable after every change.
  • 4. Watch for variable resets – Variables inside loops reset each iteration.
  • 5. Show final output clearly – Write exactly as it would appear on screen.

Trace Table Worked Example

  • Algorithm: total=0, count=1, WHILE count≤3: input number, IF number>10 THEN total+=number, count+=1, OUTPUT total.
  • Inputs: 12, 8, 15. Output: 27.
  • Trace table rows: line number, count, number, total, output.
  • Use a dash (–) when a column is not relevant; keep neat.

Common Mistakes and Tips

  • Read code exactly as a computer would – don't skip lines.
  • Use a pencil and annotate each step.
  • Don't fill in lines that just mark end of IF/WHILE (e.g., line 7, 9).
  • If only 5–6 rows used, something is likely missing.

슬라이드

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연습 문제

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  1. 1.What is the purpose of a trace table in computer science?

    Easy
    • ATo follow the values of variables as a program runs
    • BTo draw a diagram of the program's structure
    • CTo convert high-level code to machine code
    • DTo store the program's output

  2. 2.In the context of trace tables, what does the command word 'Complete' mean?

    Easy
    • AFill in the table with correct values
    • BGive the value/output/result
    • CSay why something happens or changes in the program
    • DSpot where something goes wrong or doesn't match expectations

  3. 3.Which of the following is NOT a question you should ask yourself when attempting a programming question?

    Easy
    • AWhat are the inputs?
    • BWhat are the outputs?
    • CWhat is the file size?
    • DWhat constructs will I need to use?

  4. 4.In CIE pseudocode, which function is used to convert a string to lowercase?

    Easy
    • ALCASE()
    • BUPPERCASE()
    • CLOWER()
    • DTOLOWER()

  5. 5.Given the string Quote = 'Learning Never Exhausts The Mind', what is the result of SUBSTRING(Quote, 25, 8)?

    Medium
    • A'The Mind'
    • B'The Min'
    • C'he Mind'
    • D'The Mind' (including the space)

  6. 6.In a trace table, what is a common mistake that students make?

    Easy
    • ASkipping or misreading a line
    • BUsing too many rows
    • CWriting the output first
    • DUsing a pencil

  7. 7.In the trace table worked example with inputs 12, 8, 15, what is the final output?

    Medium
    • A27
    • B35
    • C20
    • D12

  8. 8.When completing a trace table, why should you use a new row whenever a variable or output changes?

    Easy
    • ATo accurately track each step of the program's execution
    • BTo make the table look longer
    • CTo avoid using too many rows
    • DTo confuse the examiner

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