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  • 1. Microsoft Visual Basic 2005 BASICS Lesson 5 Data Types and Variables
  • 2. Objectives
    • Describe the purpose of data types and variables.
    • Use the AutoSize property.
    • Declare and use variables.
    • Describe the scope of variables.
    • Describe the Object data type.
  • 3. Data Types
    • Computers are all about data.
    • Visual Basic supports a certain set of data types.
    • You can choose to store data in memory locations called variables.
    • Variables
      • Can be used to store and manipulate all kinds of data
  • 4. Data Types (cont.)
  • 5. Using the AutoSize Property
    • The AutoSize property
      • Adjusts the size of a control to fit its contents
    • Label control example
      • The AutoSize property will shrink or enlarge the label to fit the text.
  • 6. Using the AutoSize Property (cont.)
  • 7. Using the AutoSize Property (cont.)
  • 8. Declaring Variables
    • Using a variable in your programs
      • Let the compiler know
        • That you want to set up a memory location as a variable
        • What you want to call the variable
        • What data type you want the variable to have
    • Declare a variable
      • Use the Dim statement
  • 9. Rules for Naming Variables
    • When naming variables, keep the following rules in mind:
      • Variable names must begin with an alphabetic character.
      • Following the first character, letters, numbers, and underscores are allowed.
      • Variable names cannot include spaces.
      • Variable names can be 255 characters long.
  • 10. Rules for Naming Variables (cont.)
  • 11. Using Variables
    • Variables can be used in the same way as labels and text boxes.
    • Use the assignment operator to assign a value to a variable.
      • You can also assign hard-coded values to a variable.
  • 12. Using Variables (cont.)
    • Use mathematical operators to perform calculations with numeric variables.
    • Output the value in a variable.
      • Assign the value to a label.
  • 13. Using Variables (cont.)
  • 14. Using Variables (cont.)
  • 15. Scope
    • The term “scope” refers to the reach of a variable.
    • General rule
      • You should declare variables as locally as possible.
  • 16. Three Levels of Scope
    • Levels
      • Local variable
        • Declared within an event procedure
      • Form-level variable
        • Declared in the Declarations section of a form’s Code window
      • Global variable
        • Declared in a code module’s section
  • 17. The Declarations Section
    • Access the Declarations section
      • Select (Declarations) from the Method Name list that appears at the top of the Code window.
  • 18. The Declarations Section (cont.)
  • 19. The Declarations Section (cont.)
  • 20. Using the Object Data Type
    • Object data type
      • Very flexible
      • Can store many different types of variables
    • Object variables
      • Can be declared by specifying the Object type
      • Or by declaring a variable without a type
  • 21. Summary
    • Data can be in the form of numbers, text, dates, pictures, and even sound.
    • Visual Basic supports a set of data types. There are data types for whole numbers, floating-point numbers (decimals), text, dates, and more.
    • You can choose to store data in memory locations called variables.
  • 22. Summary (cont.)
    • The AutoSize property will adjust the size of a control to fit its contents.
    • The first step to using a variable is to declare it using the Dim statement.
    • When naming variables, keep the naming rules in mind. It is a good idea to use naming prefixes to identify the data type of the variable.
  • 23. Summary (cont.)
    • You can assign values to variables using the assignment operator.
      • You can also use the other mathematical operators with numeric variables.
    • A variable’s scope indicates the procedures that have access to the variable. A variable’s scope can be local, form-level, or global.
  • 24. Summary (cont.)
    • The Declarations section of a form’s Code window allows you to declare form-level variables.
    • The Object data type can hold many different kinds of data, but is less efficient than specific data types.