outline

Conditions

• Conditions are expressions that can be evaluated as true or false.
• Conditions are NOT an equation.
• Conditions usually compare a value to a variable - can also be a variable to a variable.

If - Then - Else

• This is the most basic condition
• This is used for simple branching

Syntax

• Simple form: IF expression Then command
  If userName = "Wally" Then MsgBox("Hello, Wally")
• Block form:
  IF expression Then
     code
  ELSE
     more code
  END IF

Select Case

• Select Case is used for multiple branching
• Tests one variable for multiple values

Syntax

• SELECT CASE variable
     CASE value 1
       Basic statement
     CASE value 2
       Basic statement
     CASE ELSE
       Basic Statement
     END SELECT

Example

• Dim Year as String
  Year = InputBox "In which year was 'Gone with the Wind' produced?"
  Select Case Year
      Case "1937"
        MsgBox "WAY too early"
      Case "1938"
        MsgBox "A little too early"
      Case "1939"
        MsgBox "PERFECT!!!"
      Case Else
        MsgBox "Your are WAY off!!"
  End Select

Do..Loop

• This is used for conditional looping
• DO and LOOP keywords mark the beginning and the end of the loop.

Syntax

• DO [WHILE, UNTIL, or NOTHING] [Condition for WHILE or UNTIL]
      code inside loop
  LOOP [WHILE, UNTIL or NOTHING] [Condition for WHILE or UNTIL]

WHILE Condition

• The loop continues as long as the condition is TRUE
• The loop ends when the condition is FALSE

UNTIL Condition

• The loop continues as long as the condition is FALSE
• The loop ends when the condition is TRUE
• This is the opposite of WHILE

Placement of the Condition

• DO - the condition is evaluated BEFORE the code is run
• It is possible to skip code
• Is usually necessary to initialize a sentry variable
  - a sentry variable is a counter type variable

Loop

• Code runs at least once before condition is checked
• The initialization often occurs in code
• Is more commonly used

Example: Until at bottom

• Dim Answer as Integer
  Answer = 0
  Do
       Answer = Val(InputBox ("What is 2+3"))
  Loop Until Answer = 5

Example: While at top

• Dim At_Peace as Boolean
  At_Peace = True
  Do while At_Peace = False
       Launch_Missles(Russia)
  Loop

Example: While at bottom

• Dim At_Peace as Boolean
  At_Peace = True
  Do
       Launch_Missles (Russia)
  Loop while At-Peace = False

3 things to consider

• What is the condition?
• Do I need the condition at the top or the bottom?
• Do I want a while or until condition?

For/Next Loop

• This is a simpler and older loop
• Used for counting
• You must know how many times you will do the task (either directly or in a variable)

Syntax:

• For counting_variable = 1 to limit [STEP steps]
       BASIC code?..
  NEXT counting_variable

Example: Simple counting loop

• For I = 1 to 10
  MsgBox Str (I)
  NEXT I

Example: Counting backwards

• For I = 10 to 1 Step -1
       MsgBox Str (I)
  Next I

Using the counter inside the loop

• For Xpos = 0 to MyForm.Width Step 100
       ImgCar.Left = Xpos
  Next XPos

Other techniques you will need

• CLS Method
•    Atached to picture boxes and forms
•    Allows you to clear the object
•    Derived from the old CLS command
• Syntax: ObjectNaame.cls

Print method

• Attached to picture boxes, forms and printer object
• Allows you to print a value directly to the object
• Derived from old PRINT command
• Syntax: ObjectName.Print Value
• Value can be a string or numeric, direct or variable name