CS 40 - Lecture 10

Cover page image

Cay S. Horstmann

What Do You Do?

You are in an elevator at SJSU. The door opens, and a foreign student wearing a head scarf enters.
A fellow student--a large fellow--raises his fist and screams "terrorist" at her.
What do you do?
ActiveLecture.org

Lecture 9 Recap

Artificial Intelligence: science and engineering of making intelligent machines
Examples: autonomous cars, chess playing, resume scanning
Methods: deduction rules, statistics, simulated neurons
Unsolved problems: language translation, understanding speech or images

Alice (From Lecture 1)

Programming language
Animate characters, tell stories
Drag and drop; no frustrating syntax errors
Teach programming concepts, then move on to a “real” language
Developed for middle school girls
Will it work in a college setting?

Concept 1: Programming

Programming: Create a sequence of steps that can be replayed

Concept 2: Objects and Methods

Objects have observable behavior. Ex. toaster
Methods are invoked on objects. Ex. toaster.move

Concept 3: Design

Object-oriented design: Put the methods with the responsible objects
Top-down design: Break story into scenes, scenes into tasks, etc.

Concept 4: Decisions

condition: an expression that is either true or false
if-else decision: Either execute the statements in the if part or in the else part.

Concept 5: Repetition

simple loop: Repeat statement n times (or forever)
while loop: Keep repeating the statements while a condition is true

Match Concepts with Alice Samples

Concept	draw line in ActiveLecture.org	Alice Program
Put methods with responsible objects		Evil step sister eats closest cookie
Simple loop		Valley of the toasters
Top-down design		T. Rex eats toaster when it is close
if-else decisions		Toaster hops around circle
while loop

Go to http://ActiveLecture.org, enter lecture #, click Discuss
Then click on Add Image.
Applet is downloaded. Buttons appear on top-right corner of screen.
Click on the "World + Scribble" icon
Draw lines with mouse
Click on the "Stamp" icon

Concept 6: Implementing and Calling Methods

method: a named sequence of instructions
parameter: an input to a method
method call: a statement that contains the method name and parameter values
calling a method: setting the parameters and executing the method instructions

Concept 7: Variables

variable: holds a value
initializing the variable: setting the first value
instance variable: defined in object
local variable: defined in method

Concept 8: Classes

object: item that can be manipulated in program (has instance variables, methods)
class: set of objects with the same behavior
instance of a class: an object of the class

Match Concepts with Alice Samples

Concept	draw line in ActiveLecture.org	Alice Program
Parameters		Voting machine
Local variables		Combo lock
Instance variables		"Eat cookie" in homework 2
Classes		Spider robot walk

Reminders

Exam 1 is on Thursday
Alice, voting machines, artificial intelligence
Some multiple-choice
One question "what does this program do?" (Will be a modification of one of the lab exercises. Hint: Review labs)
One question "Modify this homework problem to do x". Hint: Review sample solutions