1. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Exam scores by range 3-1

2. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Exam Scores by Grade – Recorded as 87 points possible, so 90/80/65/50 % of possible 3-2

3. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Scores On average people dropped 5 points from the first test. Since I counted this as 5 points less, the percents are very close. However, some of you made huge increases or decreases in your scores. I think we need to offer a third (optional) test which replaces the lower of the two scores. 3-3

4. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Optional final 90 points possible. Comprehensive. Given during final exam period. Will make it up to be a regular one hour exam – which you have an hour and a half to complete. (will take place after “project quiz” on final day) Replaces the lower of the two exam scores (so if you do worse, it hurts you) Must notify me (by email) by April 24 th if you intend to take it. Most of you should NOT take the optional final. 3-4

5. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Success Eagle grades are “fairly” close. The cutoffs may lower a tiny bit (say a half of a percent). All that is left now is assignments, participation points, and the final project. It is possible to be “practically perfect” on the programs – so that is a great way to improve your standing. You might do a little bit extra – as that may make up for some small mistake elsewhere. Don’t neglect participation points (surveys and questions) as they are weighted at 5% of the total points – which is a big swing. 3-5

6. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Starting Out with Alice: A Visual Introduction to Programming First Edition by Tony Gaddis Chapter 11: Variables, Functions, Math, and Strings

7. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-7 Chapter 11 Objectives To understand: –what the many variables are and when and how they are used –what three things are specified when creating a variable –how a function differs from a method –where an object’s functions are listed –what primitive functions are –what operators are and how are they used –how math expressions are used in programming –what a collision is and ways to avoid them –what a string and string concatenation are

8. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Homework for Friday, Beetle band. Each Beetle, plays a solo. Jumps up and down twice its height. Can copy instructions and substitute names. How can we make it easier – more reusable? 3-8

9. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-9 Variables Programs may need to store data when running and it stores that data in a variable A variable is a named storage location in the computer’s memory Scope: the area where the variable is known 3.1

10. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-10 Variable Types – like the “jocks” in your high school (what they look like and what they do) Local variables –belongs to a specific method –used only by the instructions that the variable belongs to –when a method stops, the variables cease to exist World-level variables –variable that belongs to the world 3.1

11. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-11 Creating Local Variables Local variables belong to a specific method (such as world.my first method) Variable declarations require 3 things: –name –type –initial value name type value 3.1

12. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-12 Names and Types and Initial Values Variable Names –Must be unique within the method –Should be meaningful and reflect the variable’s purpose –Named using camelCase Variable Types –Numbers, Boolean, Objects, Other (such as String, Color, or Sound) –Numbers normally aren’t stored as numbers unless you will do comparisons/math with them Initial Value –Value initially stored in the variable 3.1

13. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley What are the types of the following Whether you read the chapter or not Your library card number Your phone number The height of the tallest person The tallest person The name of the tallest person If you are awake Your grade in the class 3-13

14. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-14 Variables Tile appearance shows the type of variable – note the square before the variable name. Creating the variable is called variable declaration 3.1 variable area

15. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-15 Variable Assignment Variables have an initial value to protect against errors Initial value held until a different value is assigned New values can be assigned while the method is running –Set instructions can be created to store (or set) different values –Request to set a value occurs when variable tile dropped into Methods Editor. “Set value” is the first choice. –Sometimes you have to put in a dummy value to be replaced later. 3.1

16. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-16 Functions Like a method – but returns a value. Example, give me the area of a figure. Each object has a set of primitive functions List of functions is categorized –Boolean logic (true/false) –Math –Random –String –Ask user –Mouse (distance from edge) –Time –Advanced math –Other 3.2

17. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-17 Snowman who jumps up and down his height. Other variables?

18. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-18 Asking the User for Input World has three primitive functions that ask for user input Each function is displayed in a dialog box 3.2 Is it Yes or is it No?

19. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-19 Primitive Object Functions Each object has primitive functions different from the world’s primitive functions –Proximity –Size –Spatial relation (left of, right of, …) –Point of view –Use “print” (from bottom of screen) to see what is returned. 3.2

20. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-20 Creating Math Expressions Math Operators are used to create math expressions Math expressions perform a calculation and return a value Operands appear on both sides of an operand payRate * hoursWorked –“payRate” and “hoursWorked” are operands This interface is a bit awkward. “Just typing” would be much easier – but error prone. If you try to drag an illegal operand, it just ignores you. 3.3 OperatorDescription +Addition -Subtraction *Multiplication /Division

21. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Sample Problem We want the horse and rider to jump over the fence. See horseJump.a2w Suppose we want the horse to jump a random height and fall down if it doesn’t jump high enough. –Notice “as seen by” after horse has fallen. –Notice if/else statement 3-21

22. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-22 Working with Strings and Text A string is a sequence of characters Strings represent: –names –addresses –messages –etc. 3.4

23. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-23 Asking the User to Enter a String World’s primitive function can ask user to enter string (text) The function returns the text the user enters Joining separate sets of strings is called concatenation –“Hello” joins with the user’s name What’s your name? Hello, Jo! 3.4

24. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-24 Joining Strings String Concatenation –Joins string a with string b (see world functions) –Strings a and b are arguments –Does not change the values of strings a or b…but combines the two strings Strings are NOT just text… but any alphanumeric characters Can convert numbers to a string for use as well 3.4

25. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley At seats, prompt user for name 3-25

26. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-26 world.concert ( ) first =, name = Hello, greeting = Hello good buddy print ( lennonBeetle 's position ) name set value to ( ask user for a string question = Enter a name: ) name set value to ( greeting joined with name ) lennonBeetle say name Methods When you “ask user” for a string, system will want a prompt. In this case, the prompt was “Enter a name:”

27. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3-27 Text can be added to Alice worlds 3D text option is available at the end of the local gallery 3.4