1. CSE 115 / 503 Introduction to Computer Science I
Pew Learning and Technology Workshop
4/16/2017June 4, 2001
CSE 115 / 503 Introduction to Computer Science I
Carl Alphonce
219 Bell Hall

2. Lecture #3 Agenda Review Problem solving Reminders analysis
decomposition
modeling
Reminders
Fall 2005
CSE 115/503 Introduction to Computer Science I

3. Review (1 of 3) Objects have:
properties, which together define the internal state of the object, and
behaviors, which determine
what services the object is prepared to provide to other objects, or to put it another way
what messages the object will respond to.
Fall 2005
CSE 115/503 Introduction to Computer Science I

4. Review (2 of 3)
Different objects can have different sets of properties and behaviors; our activity showed objects with both different properties and different behaviors.
Object-oriented (OO) programs are viewed as systems of interacting entities.
Fall 2005
CSE 115/503 Introduction to Computer Science I

5. Review (3 of 3) OO has its roots in the language Simula
Simula was designed in early 1960’s by
Kristen Nygaard
Ole-Johan Dahl
They jointly received computing’s highest awards for their work
OO is about forty years old!
Fall 2005
CSE 115/503 Introduction to Computer Science I

6. Questions?
Fall 2005
CSE 115/503 Introduction to Computer Science I

7. Problem solving Problem solving is a methodical process
Basic processes of software construction (simplified, for now):
analysis to build a specification
decomposition
modeling
implementation
Fall 2005
CSE 115/503 Introduction to Computer Science I

8. Example (1 of 4)
Problem:
I am tired of walking everywhere. I want a device which will transport me from place to place.
Fall 2005
CSE 115/503 Introduction to Computer Science I

9. Analysis
Given a problem (expressed in the customer’s terms), how do you figure out what is needed to solve it?
Communicate with client to uncover requirements.
Result is a specification, expressed more formally, that spells out in detail what the final product must do.
Fall 2005
CSE 115/503 Introduction to Computer Science I

10. Specification
“It should list each component of the system, including its capabilities and properties, and its interactions with other components.”
Brown notes
Fall 2005
CSE 115/503 Introduction to Computer Science I

11. Designing a Model
The specification must be translated into a form that is understandable by a computer.
To do this we first design a model of the system (a “simplified representation”, i.e. an abstraction)
Our models will use the building blocks of OO programming (objects and relationships between objects) to represent components of the system.
Fall 2005
CSE 115/503 Introduction to Computer Science I

12. What should go into the specification?
Example (2 of 4)
Recall the problem:
I am tired of walking everywhere. I want a device which will transport me from place to place.
What should go into the specification?
Fall 2005
CSE 115/503 Introduction to Computer Science I

13. To answer that we need to ask more questions:
Example (3 of 4)
To answer that we need to ask more questions:
How far does it need to go?
How quickly?
Indoor/outdoor
Across water?
Human powered or not: what fuel source?
Cost?
Size?
Controls?
Fall 2005
CSE 115/503 Introduction to Computer Science I

14. Example (4 of 4)
Once specification is available, we can build a model.
Once the model is OK, we can build a system.
This can be done incrementally (design power source independently of entertainment system) and iteratively (specification/model/product can be refined through several iterations).
Fall 2005
CSE 115/503 Introduction to Computer Science I

15. Next step? So we have a model – now what? We need to implement it!
We will implement our models using a computer programming language called Java.
Fall 2005
CSE 115/503 Introduction to Computer Science I

16. Reminders No class Monday: Labor day
Read chapter 1 of the Brown notes BEFORE coming to class on Wednesday
Fall 2005
CSE 115/503 Introduction to Computer Science I

17. Questions?
Fall 2005
CSE 115/503 Introduction to Computer Science I