Object-Oriented Programming is a core part of IB Computer Science. Revise the key concepts and common mistakes below, then lock them in with the free games.
Class and objectClass is template; object is instance with state and behaviour; Simula 1967 introduced OOP concepts.
EncapsulationBundling data and methods; restricting direct access via private fields and public getters/setters.
InheritanceSubclass inherits attributes and methods from superclass; allows code reuse and is-a relationships.
PolymorphismOne interface, many implementations; method overriding and overloading; runtime dispatch.
Abstract classCannot be instantiated; declares interface and may include partial implementation; concrete subclasses required.
UML class diagramBoxes show class name, attributes, methods; arrows show inheritance and association (OMG standard 1997).
InterfaceContract of method signatures to implement.
Concrete classProvides full implementation; instantiable.
UMLUnified Modeling Language for software diagrams.
Class diagramShows classes, attributes, methods, relations.
AssociationLink between classes - composition, aggregation.
Design patternReusable template for design problems.
SingletonEnsures one instance globally.
ObserverSubjects notify subscribers on change.
Questions where students often pick the tempting wrong answer — make sure you know the right one: