AP CompSci Unit 4

Expression:

a combination of operators and values that evaluates to a single value

Variable

holds one value at a time. A reference to a value (or value that results from evaluating an expression) that can be used repeatedly throughout a program

• Creating variables

  • Create them once (use var once)

  • Put them at the top

  • Create outside functions or onEvents

Global vs. Local Variables:

• Global

  • Permanent. Can be used anywhere in your code (var is outside onEvent)

• Local

  • Temporary. Can be used only in the part of the code where it was created, deleted once code is done running (var inside onEvent)

Assignment Operator:

allows a program to change the value represented by a variable (<-- or =)

Debugging

The process of finding and fixing problems in a code

• Describe the problem

  • What do you expect it to do?

  • What does it actually do?

  • Does it always happen?

• Hunt for bugs

  • Are there any warnings or errors?

  • What did you change most recently?

• Try solutions

  • Make a small change

• Document as you go

  • What have you learned?

  • What strategies did you use?

  • What questions do you have?

Error Types:

• Syntax Error

  • Your code doesn’t follow the rules of the programming language

    • Name not in quotes, using variable that doesn’t exist…

• Logical Error

  • Your code follows the rules of the programming language but doesn’t do what you intend

    • If-else statements in wrong order, updating wrong property…

Information can be stored as…

• Numbers (no quotes)

• Strings (quotes)

Boolean Expression:

 evaluates to true or false

Boolean Value

True or false

Comparison Operators:

<, >, ==, <=, >=, !=

Logical Operators

&&, ||, ! 

Operator

+, -, x, /

Truth Tables

• && (and)

  • True &&  True = True

  • True && False = False

  • False && True = False

  • False && False = False

• || (or)

  • True || True = True

  • True || False = True

  • False || True = True

  • False || False = False

• ! (not)

  • ! True = False

  • ! False = True

onEvent

used when “when” is used. When the user does something

Conditional Statement:

used if “if” is used. Happens if a boolean expression evaluates to true

Function

a named group of programming instructions. Also referred as a procedure

• Function updateButton( ) { → 

     setProperty(

     setProperty(

     setProperty(

}

Function Call:

a command that executes the code within a function

• updateButton( ); →