Variables and Constants

1
Variables and Constants

• Business 92
• Fall 2007
• Roldan

2
Variables

• Stores data temporarily in the computers memory
• Key to working with user input
• Allows a program to proceed based on user inputs
  and actions
• First step Declare the Variable

3
Declaring Variables

• You declare variables to
• Tell the computer which parts of your program
  have permission to store and retrieve the data in
  the variable
• Tell the computer the name of the variable
• Tell the computer what type of information that
  variable is allowed to hold
• Basic syntax
• ScopeType VariableName as DataType
• Scopetype can either be Dim or Public
• Dim allows the variable to be modified by only
  one part of the program
• Public creates variables that can be modified
  by all parts of the program
• VariableName keep it simple letters numbers
  only, no spaces or punctuation marks
• DataType tables of datatypes can be found in
  pages 234, 235, 236, 237, and 238

4
Declaring Constants

• Constants always contain a fixed value
• Basic syntax is
• Const constantname as datatype constantvalue
• Enables you to have only one place where the
  value of the constant is to be updated and the
  change ripples through your program
• Constants also allow you to have descriptive
  names for fixed values you use in your program

5
Code Anatomy
6
Variable only for the Form
Dim Statement for Dogage in Code behind Form
7
Variable for your entire Program

• Declare a public variable in a module
• Select ProjectAdd Module then click ok to add
  Module1.vb to your program
• Code AnatomyPublic DogAge as Integer

8
Using a Public Variable

• A Public Variable is can be edited and used by
  any part of your program
• Add a second form and link code to a button on
  this second form to display the value for DogAge
• Add a button to Form1 to show Form2

9
In Class Work

• Complete the tutorial on page 244 if you have not
  yet done so.
• Add a second form to your tutorial program to use
  the data collected in form1 (see Slide 8)
• Add at least two variables and one constant to
  your application to capture user input
• one variable should be local to a form and the
  other should be a public variable
• Build an executable for your tutorials and
  application and submit in your flash drive
• Talk to me about your application if you are
  having trouble figuring out how to fit these
  elements to it