1. Introduction to Visual Basic (VB)

2. Topics 1. What is VB? 2. What is Event-Driven?
3. What is Object-Orientation?
4. Objects used in VB
5. VB objects naming practice
6. Files in VB
7. OOED Programming process
8. VB statements
9. VB Help

3. What is VB? A windows-based system using objects responding to events
An objected-oriented event-driven programming language

4. Event-Driven
Procedural languages – run from start to finish with no human intervention
Basic, COBOL, FORTRAN, C
Event driven languages - waits for an event to occur before taking any action
Example of event
The press of a key on the keyboard
Movement of the mouse
The click of a mouse button
Programming in Windows is usually termed event-driven programming

5. Objects
Reusable software components that model items in the real world
e.g. GPA calculator, Tax calculator
They are self-contained modules that combine data and program code which pass strictly defined messages to one another

6. Encapsulation
The capability of an object to hide its internal workings from other objects.
In VB, programmers does not need to know what is going on inside the object, but only need to know how to work with the object’s properties and methods
How many drivers are mechanics?

7. Object-Oriented Event-Driven Programming (OOED)
OOED uses objects in the program and runs only after the Events occur
OOED is easier to work with
Users can combine multiple objects to create new systems or extend existing ones

8. Starting VB from your computer …
Toolbox [p. 27]
Project Window [p. 28] useful icons
Properties windows [p. 30]
How to Add Controls [p. 36]
How to Add Code [p. 39]
The toolbar icons [p. 43]

9. 1st Project (ShowName) A Form Three Command Buttons One Text Box
Click Me
Exit
One Text Box
One Label

10. Forms and Controls as Objects
Forms and Controls are two kinds of objects you may use in VB
A form is a virtual blank space to design the user interface for a VB application
The tools that you use to construct the user interface are controls
E.g. command button and textbox etc.

11. VB objects naming practice:
Start the name with a standard object abbreviation
cmd = command button, txt = text box, frm = form.
Finish the name with a descriptive word of the objects purpose
Spaces and special characters are not allowed in an objects name. (E.g. cmdCancel)
Examples might be:
frmMain.BackColor = vbRed
txtState.Text = ""

12. Features of Objects
The programmer can manipulate the object through the use of three key object features:
properties
methods
events

13. Object Properties A property is a named attribute of an object.
Using an analogy to English grammar, if an object is thought of as a noun, then a property may be thought of as an adjective.
Used to change the appearance of objects.
An example of the relationship between objects and properties using an everyday object:
shirt.color = "Green“
shirt.launder = "Clean“
We use dot (“.”) notation

14. Setting Values of Properties
During design time, properties may be set in the Properties Window.
You are in “Design Time” when you are designing the project and adding code
Some properties may be set or modified during run time.
You are in “Run Time” when you click the VCR Run icon

15. Object Methods
A set of predefined activities that an object can carry out.
The syntax for using an objects method is:
object.method
A method is a verb that can be carried out by the object.
For the various VB objects, there are usually several methods already available.
Or advanced programmers can create their own methods.

16. Methods Example Real life example A Visual Basic example dog.eat
dog.bark
dog.run
A Visual Basic example
E.g. frmMain.hide

17. Object Event VB example
An action taken by the object when notified by a message
Or, user actions taken on the object that provokes a response from the object.
Examples
Soccer ball: kicking, throwing, holding etc.
Cat: feeding, hitting, calling etc.
mouse click, form load, or key press.
VB example
Private Sub cmdsubmit_Click() …
End Sub

18. Files in Visual Basic
All projects in VB have a .vbp (project) file and at least one .frm (form file) file.
Always save .frm files first and then save project files. Use File|Save or File|Save as… commands for this purpose or click Disk icon on toolbar.
Projects with graphics also have .frx (binary form) files. They are saved automatically.
Module files have a .bas extension and are pure code files.

19. Save files Save early. All three types can and should have same names.
Important!
Save early.
All three types can and should have same names.
Eliminate prefix (eg.frm)

20. Add graphic Retrieve your 1st project from your disk Use image control
Select a graphic
Change the size of graphic
Stretch property of image control
Save the project

21. Save it Use your last name
Eg. chen.frm, chen.vbp, chen.frx
Create a folder in your disk composed of your name
Copy files to your folder
Drag the folder to:
W:\apps\classes\mist4600\homework\ Dchen\testfile folder

22. OOED Programming Process
A six step process for writing an OOED computer program:
1. Define problem.
2. Create interface
3. Develop logic for action objects
4. Write and test code for action objects
5. Test overall project
6. Document project in writing

23. More Practice (step 1 to 3 only)
Circle problem revisit
I: radius
P: calculate circumference, calculate area
O: radius, circumference, area
Payroll problem revisit
I: employee name, pay rate, and hours worked
P: calculate gross pay
O: gross pay

24. Comments
To explain the purpose of a program, or a statement, a comment statement is added
For yourself and others
Any statement beginning with an apostrophe or REM is a comment
Comments can be added to end of statements using apostrophe

25. VB Statements A statement is a reserved word
Statements are instructions that are built into the Visual Basic language
Some examples are: End
Option Explicit
Private Sub
Dim

26. Visual Basic Help There are three types of Help:
Help menu option
context-sensitive help
and Auto Help
In VB 6, Help uses the familiar Internet Explorer browser interface for the first two types of help.
You can seek help by selecting Contents, Index, or Search from the Help menu item

27. Context-Sensitive and Auto Help
With context-sensitive help, pressing the F1 key provides help on whatever item the cursor is located.
With Auto Help, VB tries to help you with a code statement by providing:
A list of items to complete the statement
Info on the statement you have started
Tips on the type of data you are working with