IB Computer Science HL · Year 2 · Lesson 3
Queues: FIFO operations and trade-offs
Data structures organize information so that operations are efficient, understandable and appropriate to the problem.
Paper 250 minutesB2.2.4
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Today’s targets
What you need to be able to do
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- ExplainThe concept of a queue as a “first in, first out” (FIFO) data structure
B2.2.4
Paper 2 lensMatch the depth of every response to the command term. Previously learned content can move quickly, but retrieval must still be accurate.
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Retrieve
Rapid Recall Deck
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Say the answer aloud before flipping. Mark secure knowledge quickly and spend time on the gaps.
- What does FIFO mean for a queue?: First in, first out: the earliest enqueued item is the first item removed.
- What does enqueue do to a queue?: enqueue adds an item at the rear of the queue.
- What do dequeue, front, and isEmpty do?: dequeue removes and returns the front item; front reads the next item without removing it; isEmpty checks whether the queue contains no items.
- When is a queue an appropriate data structure?: When items should be processed in arrival order, such as print jobs, service requests, or task scheduling.
- How do queue operations affect performance and memory?: Efficient implementations add at the rear and remove from the front without shifting every element; memory use grows with the number of queued items.
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B2.2.4 · Learn
Core knowledge and application
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B2.2.4Explain
The concept of a queue as a “first in, first out” (FIFO) data structure
Data structures organize information so that operations are efficient, understandable and appropriate to the problem.
Exam moveGive the mechanism or relationship and make the reasons/causes explicit.
Required detail 1Must include fundamental operations such as enqueue, dequeue, front and isEmpty
Required detail 2How queue operations impact both performance and memory usage
Required detail 3An appropriate queue for a specific problem
Assessment boundaryStacks/queues are assessed conceptually at the “explain” level; operations may be defined in an algorithmic-thinking question. Paper 2
Explain it without notes
Explain: The concept of a queue as a “first in, first out” (FIFO) data structure in the context of a scheduling application with changing data.
- Must include fundamental operations such as enqueue, dequeue, front and isEmpty
- How queue operations impact both performance and memory usage
- An appropriate queue for a specific problem
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Apply
Transfer to a new scenario
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ScenarioA scheduling application with changing data needs a design or technical decision related to today’s topic. Explain what matters and why.
- Must include fundamental operations such as enqueue, dequeue, front and isEmpty
- How queue operations impact both performance and memory usage
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Exam lens
Paper 2 practice
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Build the response before checking notesUse precise terminology and match the required depth.
- Explain: The concept of a queue as a “first in, first out” (FIFO) data structure in the context of a scheduling application with changing data.
Self-checkAnswer the exact command term. For explain, include mechanism/reason; for compare, pair criteria; for discuss/evaluate/justify, build supported reasoning and a conclusion.
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Homework
Finish the learning cycle
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IA — main task
Refine Criteria A/B/C. Use today’s lesson to make the problem specification, decomposition, algorithms or testing plan more precise where relevant.
Syllabus — 10–15 min
Repeat the recall deck and complete the lesson response prompt without model support.
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End of Lesson 3.