IB Computer Science HL · Year 2 · Lesson 15

B3.1 cumulative Paper 2 checkpoint

Object-oriented programming models a problem through classes and objects, with clear responsibilities and controlled access to state.

Paper 250 minutesB3.1.1 · B3.1.2 · B3.1.3 · B3.1.4 · B3.1.5
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Today’s targets

What you need to be able to do

2 / 7
  • EvaluateThe fundamentals of OOP
  • ConstructA design of classes, their methods and behaviour
  • DistinguishBetween static and non-static variables and methods
  • ConstructCode to define classes and instantiate objects
B3.1.1B3.1.2B3.1.3B3.1.4B3.1.5
Paper 2 lensMatch the depth of every response to the command term. Previously learned content can move quickly, but retrieval must still be accurate.
Page 2 of 7
Retrieve

Rapid Recall Deck

3 / 7

Say the answer aloud before flipping. Mark secure knowledge quickly and spend time on the gaps.

  • In OOP, what is the difference between state and behaviour?: State is the data stored in attributes; behaviour is the set of operations provided by methods.
  • Why use a UML class diagram before implementation?: It makes the planned structure, responsibilities, attributes, methods, and relationships explicit before code is written.
  • Which member type should store a value shared by every object of a class?: A static/class variable, because the value belongs to the class rather than to individual instances.
  • Which member type should store a value that differs for each object?: An instance variable.
  • How do constructor and instantiation relate?: Instantiation creates the object; the constructor initializes its starting state during that creation process.
  • How do encapsulation and information hiding support maintainability?: They reduce dependence on internal implementation details, so internals can change without forcing unrelated code to change.
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Consolidate

Rebuild the topic from memory

4 / 7
Closed-notes retrievalReconstruct the core ideas, operations, diagrams and trade-offs before checking earlier lessons.
  • B3.1.1 The fundamentals of OOP
  • B3.1.2 A design of classes, their methods and behaviour
  • B3.1.3 Between static and non-static variables and methods
  • B3.1.4 Code to define classes and instantiate objects
  • B3.1.5 And apply the concepts of encapsulation and information hiding in OOP
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Apply

Transfer to a new scenario

5 / 7
ScenarioA library-management application needs a design or technical decision related to today’s topic. Explain what matters and why.
  • Model real-world entities using OOP concepts: classes, objects, inheritance, encapsulation, polymorphism
  • The advantages and disadvantages of using OOP in various programming scenarios
  • Classes and their methods, based on application requirements
  • Use of unified modelling language (UML) class diagrams to represent class relationships, attributes and methods, to aid effective software design and planning
  • Compare static and non-static variables and methods, including their usage and scope
  • When to use instance variables instead of class variables, and how to apply these concepts effectively in code
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Exam lens

Paper 2 practice

6 / 7
Build the response before checking notesUse precise terminology and match the required depth.
  1. Evaluate: The fundamentals of OOP in the context of a library-management application.
  2. Construct: A design of classes, their methods and behaviour in the context of a library-management application.
  3. Distinguish: Between static and non-static variables and methods in the context of a library-management application.
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

7 / 7

IA — main task

Continue Criterion D development. Keep code readable, record meaningful implementation decisions, and maintain testing/evidence notes as you work.

Syllabus — short

Complete one targeted Paper 2/Paper 1 retrieval task from today’s lesson.

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End of Lesson 15.