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Abstraction hides complex implementation details and shows only the essential features of an object.

Two Levels of Abstraction

Class abstraction: Hide implementation behind a clean interface
Physical abstraction: Abstract base classes with pure virtual functions

Why Abstract?

Reduce complexity for the user
Focus on WHAT an object does, not HOW
Allow implementation changes without breaking code

Example

A car driver uses steering wheel and pedals (interface) without knowing how the engine works (implementation).

Abstract Classes

Contain at least one pure virtual function (= 0)
Cannot be instantiated directly
Serve as templates for derived classes

class Shape {
public:
    virtual double area() = 0;  // Pure virtual
    virtual void draw() = 0;    // Pure virtual
};

Interfaces in C++

An interface is a class with ONLY pure virtual functions. C++ doesn't have a separate interface keyword, but this pattern is common.

Key takeaway: Abstraction hides complexity behind a clean interface — use abstract classes and pure virtual functions to define contracts that derived classes must follow.

Abstraction hides complex implementation details and shows only the essential features of an object.

Two Levels of Abstraction

Class abstraction: Hide implementation behind a clean interface
Physical abstraction: Abstract base classes with pure virtual functions

Why Abstract?

Reduce complexity for the user
Focus on WHAT an object does, not HOW
Allow implementation changes without breaking code

Example

A car driver uses steering wheel and pedals (interface) without knowing how the engine works (implementation).

Abstract Classes

Contain at least one pure virtual function (= 0)
Cannot be instantiated directly
Serve as templates for derived classes

class Shape {
public:
    virtual double area() = 0;  // Pure virtual
    virtual void draw() = 0;    // Pure virtual
};

Interfaces in C++

An interface is a class with ONLY pure virtual functions. C++ doesn't have a separate interface keyword, but this pattern is common.

Key takeaway: Abstraction hides complexity behind a clean interface — use abstract classes and pure virtual functions to define contracts that derived classes must follow.