Ppt lesson 05
- 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
- 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.
- 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.