1. MIS 324 -- Professor Sandvig MIS 324 Professor Sandvig
2/5/2018
Design Goals
MIS 324
Professor Sandvig

2. MIS 324 -- Professor Sandvig
2/5/2018
Overview
Design Goals
Terminology
Encapsulation
Abstraction
Loose coupling
How implemented in C#
Classes
Variable Scope

3. Design Goals Applications getting more complex
Lines of code:
Chrome browser: 5 million
Android OS: 12 million
Facebook site: 60 million
2016 Ford pickup: 150 million
Google: 2 billion
Need to minimize complexity

4. Design Goals Minimize complexity Modularity Reusability
Compartmentalize code into classes
Hide details inside
Class interfaces expose only what is needed
Modularity
Each class has single purpose
Reusability
Maintainability
Minimize amount of code
Minimize dependencies

5. Design Goals Legos analogy: Modular Reusable Simple interface
Each piece has single purpose
Reusable
Pieces can be used in multiple products
Simple interface
Maintainable

6. Encapsulation Fundamental principle of OOP Code wrapped inside classes
Hide implementation details
Reduce complexity

7. Encapsulation Also called information hiding Exposes simple interface
Hides implementation details
Exposes simple interface
Reusable

8. Abstraction Interface provided to outside Corollary to encapsulation:
Encapsulation hides
Abstraction exposes

9. Abstraction Class Public members are abstraction
Private are encapsulation

10. Loose Coupling
Goal: design classes and interfaces to minimize dependencies
Each class has a single purpose
Clear relationships with other classes

11. Loose Coupling Example: dog class Clear purpose Interface:
Exposes all necessary dog properties
Validates inputs (birthdate, weight)
Hides messy details (calculating age)

12. MIS 324 -- Professor Sandvig
2/5/2018
Variable Scope
Within classes variable scope limited to control structures & children

13. MIS 324 -- Professor Sandvig
2/5/2018
Summary
Goals:
Minimize complexity
Modularity
Reusability
Maintainability
Tools
Classes
Variable scope