1. Microsoft Visual Basic 2005 BASICSyo
Microsoft Visual Basic 2005 BASICS
Lesson 5
Data Types and Variables

2. Objectives Describe the purpose of data types and variables.yo
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.
Microsoft Visual Basic 2005 BASICS

3. Data Types Computers are all about data.yo
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
Microsoft Visual Basic 2005 BASICS

4. Data Types (cont.)
Microsoft Visual Basic 2005 BASICS

5. Using the AutoSize Propertyyo
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.
Microsoft Visual Basic 2005 BASICS

6. Using the AutoSize Property (cont.)
Microsoft Visual Basic 2005 BASICS

7. Using the AutoSize Property (cont.)
Microsoft Visual Basic 2005 BASICS

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
Microsoft Visual Basic 2005 BASICS

9. Rules for Naming Variablesyo
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.
Microsoft Visual Basic 2005 BASICS

10. Rules for Naming Variables (cont.)
Microsoft Visual Basic 2005 BASICS

11. yo
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.
Microsoft Visual Basic 2005 BASICS

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.
Microsoft Visual Basic 2005 BASICS

13. Using Variables (cont.)
Microsoft Visual Basic 2005 BASICS

14. Using Variables (cont.)
Microsoft Visual Basic 2005 BASICS

15. Scope The term “scope” refers to the reach of a variable. General ruleyo
Scope
The term “scope” refers to the reach of a variable.
General rule
You should declare variables as locally as possible.
Microsoft Visual Basic 2005 BASICS

16. Three Levels of Scope Levels Local variable Form-level variableyo
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
Microsoft Visual Basic 2005 BASICS

17. The Declarations Sectionyo
The Declarations Section
Access the Declarations section
Select (Declarations) from the Method Name list that appears at the top of the Code window.
Microsoft Visual Basic 2005 BASICS

18. The Declarations Section (cont.)
Microsoft Visual Basic 2005 BASICS

19. The Declarations Section (cont.)
Microsoft Visual Basic 2005 BASICS

20. Using the Object Data Typeyo
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
Microsoft Visual Basic 2005 BASICS

21. yo
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.
Microsoft Visual Basic 2005 BASICS

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.
Microsoft Visual Basic 2005 BASICS

23. yo
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.
Microsoft Visual Basic 2005 BASICS

24. yo
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.
Microsoft Visual Basic 2005 BASICS