1. Separating Definition & Implementation

2. Goal
Modular abstractions we can use to build complex systems

3. Not Modular or Abstract

4. Function Declaration Function Declaration
return type name(parameter list);

5. Function Declaration Parameter names optional
Strongly encouraged – order matters!

6. Implementation
Functions need to be part of class to work with properties
Naked function is global – not part of any class

7. Scope Resolution
:: Scope resolution operator This::That "That is a part of This"

8. Scope Resolution
:: Scope resolution operator double Circle::getArea()… "getArea is a part of the Circle class"