This document discusses data types, variables, and variable scope in Microsoft Visual Basic 2005. It describes declaring variables using the Dim statement and assigning values to variables. Variables can be local, form-level, or global in scope. The AutoSize property adjusts a control's size to fit its contents. The Object data type is flexible but less efficient than specific data types. Rules for naming variables include starting with a letter and avoiding spaces.

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.