Cse 113 introduction to computer programming
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CSE 113 Introduction to Computer Programming. Lecture slides for Week 2. Wednesday, September 7 th , 2011 Instructor: Scott Settembre. Section 1. Recitations (Labs). Labs Begin This Week. Go to Bell hall [next to Student Union] Room 340.

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CSE 113 Introduction to Computer Programming

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Cse 113 introduction to computer programming

CSE 113Introduction toComputer Programming

Lecture slides for Week 2

Wednesday, September 7th, 2011

Instructor: Scott Settembre


Recitations labs

Section 1

Recitations (Labs)

University at Buffalo: CSE 113 Instructor: Scott Settembre


Labs begin this week

Labs Begin This Week

  • Go to Bell hall [next to Student Union] Room 340.

    • There is key card access that your card won’t open, so you will need to wait for the TA sometimes to show up to let you in.

    • If you queue in the hall, please be respectful of the offices and classrooms around you.

  • Please go to your lab.

    • It is mandatory.

    • Attendance counts towards your grade.

    • There is an end of class assessement/quiz.

University at Buffalo: CSE 113 Instructor: Scott Settembre


What do i do in lab

What do I do in lab?

  • You will be doing the chapters from the Greenfoot book, step by step.

  • Do each exercise.

    • You do not need to record your answers.

    • The assessment/quiz at the end of the class may require you to answer some questions about those exercises.

University at Buffalo: CSE 113 Instructor: Scott Settembre


When i am done what do i do

When I am done, what do I do?

  • After you go through the chapters that you need to cover, you will:

    • Work on your project.

    • Take the assessment/quiz at the end of class.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Can t i take the quiz and leave

Can’t I take the quiz and leave?

  • No.

  • Use the two hours to experiment and work on your project.

    • If you at some point become done with your project, then work on it more.

    • Think of your project as an art piece, Leonardo da Vinci said that “art is never finished, only abandoned.”

    • When your project is due, that is when you are done! 

University at Buffalo: CSE 113 Instructor: Scott Settembre


For the first week in recitaiton

For the First Week in Recitaiton

  • For the week of September 7th

    • Please read chapter 1 and chapter 1 exercises.

    • Please read chapter 2 and chapter 2 exercises.

    • Please finish by taking the assessment/quiz.

    • At that point, for this week only, you can leave early!

  • The first project will be assigned next week.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Greenfoot interface

Section 2

Greenfoot – Interface

University at Buffalo: CSE 113 Instructor: Scott Settembre


Demonstration

Demonstration

  • You will become more familiar with the interface when you go hands-on with the book in the lab.

  • I will demo the interface here to show you around.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Greenfoot chapter 2

Section 3

Greenfoot – Chapter 2

University at Buffalo: CSE 113 Instructor: Scott Settembre


Chapter 2

Chapter 2

  • In this chapter you will learn:

    • How to start writing code.

    • How to find out what methods you can use.

    • What an “if”-statement is! (Probably the most important control statement you will learn.)

University at Buffalo: CSE 113 Instructor: Scott Settembre


What is inheritance

What is “inheritance”?

  • It is the “is-a” relationship between classes

  • For example:

    • “A dog is-a mammal”

    • “A chiuaua is-a dog”

  • This means that a dog “inherits” all the features that a mammal may have.

  • “Sub-classes” (see last weeks notes) inherit their properties and methods from their “Super-classes”

University at Buffalo: CSE 113 Instructor: Scott Settembre


Crab and animal classes

Crab and Animal classes

  • Notice the arrow direction in the Actor classes tree.

    • A crab is-a animal.

    • An animal is-an actor.

    • Thus a crab is-a actor too!

University at Buffalo: CSE 113 Instructor: Scott Settembre


Classes can inherit methods

Classes can inherit methods

  • The animal class has a method called “act”, so that means that the crab class will also have that method.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Cse 113 introduction to computer programming

University at Buffalo: CSE 113 Instructor: Scott Settembre


What do the methods do

What do the methods do?

  • There are many methods in the animal class:

    • “act” method, does nothing.

    • “move” method, moves the actor in a forward direction.

    • “turn” method, rotates the actor a number of degrees specified in the parameter.

    • “atWorldEdge” method, returns a boolean value indicating if the actor is at the edge of the world.

  • What we will do is make the “act” method do something, like call the “move” method.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Writing code

Writing code

  • To begin writing code, let Greenfoot do the framework for you.

    • Double-click on the class to get the editor.

    • Go to the already formed “act” signature.

    • We can add “move();” within the brackets { } to make it move.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Note brackets and semicolons

Note: brackets and semicolons

  • You need to adhere to a specific “syntax”.

  • When you write English, we need to use “,” and “.” appropriately otherwise the reader will misread what you have written.

  • It is the same thing with Java, you need to use the “{“, “}” and “;” correctly or it will not understand you.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Semicolons

Semicolons

  • A semicolon “;” indicates an end of a command.

  • It is similar to a “.” at the end of an English sentence.

University at Buffalo: CSE 113 Instructor: Scott Settembre


Brackets and code blocks

Brackets and code blocks

  • The instructions between a set of brackets is called a “code block” or the “body” of a method.

  • You must match each “{“ with a “}”

University at Buffalo: CSE 113 Instructor: Scott Settembre


Syntax errors ooops i messed up

Syntax errors: Ooops, I messed up?!

  • This will happen a lot.

  • Greenfoot with alert you to a mistake.

  • You can see if you have any syntax mistakes by compiling or running your code.

  • Note: Sometimes you will have two or more mistakes, causing your code to compile/run, but not work properly. This is not a syntax error, this is a code error.

University at Buffalo: CSE 113 Instructor: Scott Settembre


To be continued on friday

To be continued on Friday

University at Buffalo: CSE 113 Instructor: Scott Settembre


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