1. Terry Scott University of Northern Colorado 2007 Prentice Hall
Object-Oriented Programming in Python Goldwasser and Letscher Chapter 1: Cornerstones of Computing
Terry Scott
University of Northern Colorado
2007 Prentice Hall

2. Introduction: Chapter 1 Topics
Data and types.
Operations, Functions, and Algorithms.
Two algorithms for determining the greatest common divisor (GCD).
High-level programming languages.
Object-oriented paradigm.
Designing and modeling.

3. Data and Types Information is organized data Data Types
Built-in types sometimes called primitive types: most languages have
numbers,
characters,
lists/arrays.
User-defined types:created by programmer.

4. Operations, Functions, and Algorithms
Central Processing Unit (CPU) – in charge of the computer. Has limited set of instructions.
Control structures – built into a language to control the order of instruction execution.
Function – high level behavior created by the programmer.

5. Operations, Functions, and Algorithms - Continued
Abstraction – Functions allow programmer to encapsulate some operation into a chunk of code.
Algorithms - step-by-step instructions for solving a problem.
Flowchart – graphical display of an algorithm.
Algorithm for finding Greatest Common Divisor (GCD)

6. GCD: Algorithm

7. GCD Algorithm (Euclid)

8. Euclid's GCD Values for u, v, and r starting with u = 54 and v = 42
Euclid's GCD Values for u, v, and r starting with u = 54 and v = 42. Answer is 6 u v r 54 42 12 6

9. High Level Programming Languages
Kinds of Languages.
Low-level programming language:
Machine code.
Assembly code.
High-level code:
Python
C++
Many others
Source Code – code written by programmer that is converted into executable code by compiler or interpreter

10. High Level Programming Languages (continued)
Compiler versus Interpreter
Compiler generates an executable file that can be run on the computer
Interpreter generates machine code and executes it immediately one line at a time.
Syntax versus Semantics
Syntax: rules followed by a language.
Semantics: meaning of statements in a language.

11. High Level Programming Languages (continued)
Syntax error: when rules of a language are violated. These are found by the compiler or interpreter.
Semantic error (logic error). Errors not found by the computer.
Semantic errors lead to incorrect results.

12. Object-Oriented Paradigm
Object-oriented programming (OOP)
Objects and Classes.
objects are created from classes.
single object from a class is called an instance.
Data and operations on that data are encapsulated together. Unit called a class.

13. Objects Data within a class is called an attribute.
All attributes together represent the state of an instance.
Operations contained in a class are called methods.

14. Obedient Dog Sequence Diagram
This and the next slide refer to a diagram two slides ahead.
Jane and Spot are instances of Person and Dog
Vertical lines represent chronological lifetime of the instances.
Solid horizontal lines represent flow of control passing from Jane to spot

15. Obedient Dog Sequence Diagram
Rectangular boxes under Spot represent time passing while operation is being performed.
Dotted horizontal lines indicate control being passed back to Jane.
Methods are:
sit( )
liedown( )
rollover( )
fetch( )

16. Obedient Dog: Sequence Diagram

17. Obedient Dog Fetching Slippers
Next slide shows a parameter being passed to the fetch() method
The fetch method expects a parameter telling what to fetch (slippers)
The dotted horizontal line indicates that redSlippers have been fetched.

18. jane invokes: spot.fetch(slippers)

19. Instance Methods Parameter – how information is passed into a method.
Return value – how information is passed out of a method.
The parameters and return value of a method are called its signature.

20. Instance Methods Kinds of methods:
Accessors or inspectors: method that returns the value of an instance attribute.
Mutators: change value of instance attribute.
Others

21. Television Class Diagram on next slide is for a Television class.
In general these are called class diagrams.
Upper rectangle lists the attributes of the class
Lower rectangle lists the methods for the class.

22. Television Diagram: Attributes and Methods

23. Television Class Design: Methods
togglePower(): method toggles a switch – pressing flips between on and off.
toggleMute(): method toggles a switch. TV must be on to have it toggle.
volumeUp(): changes volume when TV is on and only goes until some maximum volume.

24. Television Class Design: Methods (continued)
volumeDown(): changes volume when TV is on and only goes until some minimum volume.
channelUp(): changes channel when TV is on and wraps around to lowest channel once the highest channel is reached.
channelDown() same as channel up but wraps from low channel to high.

25. Television Class Design: Methods (continued)
setChannel(number): changes channel to number if TV is on.
jumpPrevChan() changes channel to previous channel if TV is on.

26. Student Registration System
Has-a relationships: combination of objects.
Is-a relationships: inheritance between objects.
Bob has-a schedule: called composition.
Design of a student registration system: sequence diagrams on next slides.

27. Sequence Diagram for Student Registration System (1st Attempt)

28. Student Registration System Sequence Diagram (2nd Attempt)

29. Student Registration System Sequence Diagram (3rd Attempt)

30. Student Registration System Sequence Diagram (4th Attempt)

31. Class Diagrams for Independent Student and Professor

32. Student and Professor Inherit from Person
Student and Professor are both persons.
Common attributes:
name.
birthdate.
phone number.
current Schedule.
Student is-a Person and Professor is-a Person.
Student and Professor inherit from Person.

33. Student and Professor Classes Derived from Person

34. Drawable Class Diagram
Next slide shows a drawable class diagram.
Attributes:
depth.
transformation.
reference point.
Methods:
rotate.
move.
see others on diagram.

35. Drawing Package: Class Diagram

36. Proposed Hierarchy of Drawable Objects Showing Inheritance.