Levels of abstraction: Software Design

• Old times: computer programs manipulated primitive types such as numbers and characters
• Manipulating too many of these primitive quantities is too much for programmers and leads to errors
• Solution: Encapsulate routine computations to software black boxes
• Abstraction used to invent higher-level data types
• In object-oriented programming, objects are black boxes
• Encapsulation: Programmer using an object knows about its behavior, but not about its internal structure
• In software design, you can design good and bad abstractions with equal facility; understanding what makes good design is an important part of the education of a software engineer
• First, define behavior of a class; then, implement it