Meaning of Visual Basic. ... Start Program Microsoft Visual Basic 6.0 . Saving a Project :

1. A. JOSEPHINE, M.C.A.,M.Phil.,
Asst.Professor
E.M.G.Yadava Women’s College,
Madurai
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2. Objectives
 Understand the benefits of using Microsoft Visual Basic 6.0 for
Windows as an application tool.
 Understand the Visual Basic event-driven programming
concepts, terminology, and available tools.
 Learn the fundamentals of designing, implementing, and
distributing a Visual Basic application.
 Learn to use the Visual Basic toolbox.
 Learn to modify object properties.
 Learn object methods.
 Use the menu design window.
 Understand proper debugging and error-handling procedures.
 Gain a basic understanding of database access and
management using data bound controls.
 Obtain an introduction to ActiveX controls and the Windows
Application Programming Interface (API).
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3. What is Visual Basic?
 Visual Basic
Is a tool that allows you to develop Windows (Graphic
User Interface - GUI) applications. The applications
have a familiar appearance to the user.
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4. What is Visual Basic?
 Visual Basic is event-driven, meaning
code remains idle until called upon to
respond to some event (button pressing,
menu selection, ...). Visual Basic is
governed by an event processor.
Nothing happens until an event is
detected. Once an event is detected, the
code corresponding to that event (event
procedure) is executed. Program control
is then returned to the event processor.
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5. Some Features of Visual Basic
 Full set of objects - you 'draw' the application
 Lots of icons and pictures for your use
 Response to mouse and keyboard actions
 Clipboard and printer access
 Full array of mathematical, string handling, and graphics
functions
 Can handle fixed and dynamic variable and control arrays
 Sequential and random access file support
 Useful debugger and error-handling facilities
 Powerful database access tools
 ActiveX support
 Package & Deployment Wizard makes distributing your
applications simple
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6. Structure of a Visual Basic Application
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Get back to
Contents

7. Structure (continued)
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Form
Control
Button
Window
Get back to
Contents

8. 8
Frame
Option Button
Label
Window
Form
Structure (continued)
Command Button
Get back to
Contents

9. The code window
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10. Contents of thE application (the
Project)
 Forms - Windows that you create for user interface
 Controls - Graphical features drawn on forms to allow user
interaction (text boxes, labels, scroll bars, command buttons,
etc.) Forms and Controls are objects.)
 Properties - Every characteristic of a form or control is specified
by a property. Example properties include names, captions, size,
color, position, and contents. Visual Basic applies default
properties. You can change properties at design time or run time.
 Methods - Built-in procedure that can be invoked to impart some
action to a particular object.
 Event Procedures - Code related to some object. This is the
code that is executed when a certain event occurs.
 General Procedures - Code not related to objects. This code
must be invoked by the application.
 Modules - Collection of general procedures, variable
declarations, and constant definitions used by application.
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11. User Interface
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Main
Window
Tool
Box
Project
Explorer
Properties
Window
Form
Layout
Project
Window

12. Main Window
 The Main Window consists of the title bar, menu bar,
and toolbar.
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13. Start Visual Basic 6.0
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14. 14

15. Contents of the Main Window
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The menu bar has drop-down menus from which you control the operation of the Visual
Basic environment.
The toolbar has buttons that provide shortcuts to some of the menu options.

16. 16
Add
project
Add
form
Menu
editor
Open
project
Save
project
Code editor
tasks
Run
Pause
Stop
Project
explorer
Properties
window
Form
layout
window
Object
browser
Data view
window
Visual
component
manager
Toolbox

17. Toolbox
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18. 18
The Properties Window is used to establish initial property values for objects. The
drop-down box at the top of the window lists all objects in the current form. Two views
are available: Alphabetic and Categorized. Under this box are the available properties
for the currently selected object.

19. The Form Layout Window shows where (upon program execution)
your form will be displayed relative to your monitor’s screen:
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The Project Window displays a list of all forms
and modules making up your application. You
can also obtain a view of the Form or Code
windows (window containing the actual Basic
coding) from the Project window.

20. Example: Stopwatch application
The application is used to calculate the time
elapsed between two events. The user starts a
timer, once the second event tops, the user
stops the timer, the time duration is displayed.
The steps are:
1. Drawing controls
2. Setting properties of the controls
3. Writing code
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21. 1. Drawing Controls
1. Start new project
2. Draw 3 command buttons on the form
3. Draw 6 labels on the form
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22. 2. Setting properties of the controls
The properties of the controls can be modified in two different
ways:
 Setting properties during design time.
In this way you click on the object (form or control) in the form
window, then click on the Properties Window or the
Properties Window button in the tool bar.
 Setting properties during run time. In this way you can set or
modify properties while your application is running. To do
this, you must write some code. The code format is:
ObjectName.Property = NewValue
Such a format is referred to as dot notation.
For example, to change the BackColor property of a form
name frmStart, you may type:
frmStart.BackColor = BLUE
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23. Setting properties during design time
 Here we selected the form window and
clicked on the properties window.
Notice that the from name here (which
is the most important property) is
frmStopWatch.
 Object names can be up to 40
characters long, must start with a letter,
must contain only letters, numbers, and
the underscore (_) character.
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24. Setting Properties in stopwatch example
The following table shows the properties you are going to change for
the objects you put on the form.
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Name Caption Border Style
Form1 frmStopWatch Stopwatch Application 1-Fixed Single
Command1 cmdStart &Start Timing
Command2 cmdEnd &End Timing
Command3 cmdExit E&xit
Label1 Start Time
Label2 End Time
Label3 Elapsed Time
Label4 lblStart 1-Fixed Single
Label5 lblEnd 1-Fixed Single
Label6 lblElapsed 1-Fixed Single
Property
Object

25. Writing Code
 Variable Declaration
 Variables are used by Visual Basic to hold information needed
by the application.
○ Rules used in naming (declaring) variables:
I. No more than 40 characters
II. They may include letters, numbers, and underscore (_)
III. The first character must be a letter
IV. You cannot use a reserved word (word needed by Visual
Basic)
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26. Visual Basic Data Types
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Data Suffix
Boolean None
Integer %
Long (Integer) &
Single (Floating) !
Double (Floating) #
Currency @
Date None
Object None
String
Variant None

27. Private Sub Command1_Click()
a% = Text1.Text
Text2.Text = a ^ 2
End Sub
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Private Sub Command1_Click()
Static a As Integer
a = Text1.Text
Text2.Text = a ^ 2
End Sub Implicit declaration of
the variable a.
There are three ways for a variable to be typed (declared):
1. Default
2. Implicit
3. Explicit
If variables are not implicitly or explicitly typed, they are assigned the
variant type by default. The variant data type is a special type used by
Visual Basic that can contain numeric, string, or date data.

28. Option Explicit
Dim a As Integer
Private Sub Command1_Click()
a = Text1.Text
Text2.Text = a ^ 2
End Sub
Private Sub Command3_Click()
a = Text1.Text
Text3.Text = 2 * a + 5
End Sub
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Explicit declaration of the
variable a.

29. Variable Scope
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30. Global Declaration of a variable
 For the variable to be declared globally, it
should be declared in a module, to create a
module,
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31. How to Create a Module
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In the module declare the variables by writing the following line:
Global a, b, c As Long
Dim c As Integer
In this way the variables will be kept in the whole code as they
been defined.

32. The Visual Basic Language
 Visual Basic Statements and Expressions
The simplest statement is the assignment statement. It consists of
a variable name, followed by the assignment operator (=), followed by
some sort of expression.
• StartTime = Now
• Explorer.Caption = "Captain Spaulding"
• BitCount = ByteCount * 8
• Energy = Mass * LIGHTSPEED ^ 2
• NetWorth = Assets – Liabilities
Statements normally take up a single line with no terminator.
Statements can be stacked by using a colon (:) to separate them.
Example:
• StartTime = Now : EndTime = StartTime + 10
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33.  Visual Basic Operators
arithmetic operators:
 The simplest operators carry out arithmetic operations. These
operators in their order of precedence are:
Operator Operation
1. ^ Exponentiation
2. * / Multiplication and division
3. Integer division (truncates)
4. Mod Modulus
5. + - Addition and subtraction
Parentheses around expressions can change precedence.
comparison operators:
Operator Comparison
1. > Greater than
2. < Less than
3. >= Greater than or equal to
4. <= Less than or equal to
5. = Equal to
6. <> Not equal to
The result of a comparison operation is a Boolean value (True or False).
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34. logical operators
Operator Operation
1. Not Logical not
2. And Logical and
3. Or Logical or
 The Not operator simply negates an operand.
 The And operator returns a True if both operands are
True else, it returns a False.
 · The Or operator returns a True if either one of its
operands is True, else it returns a False.
Logical operators follow arithmetic operators in
precedence.
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35. Visual Basic Functions
Some of the built in visual basic functions are given here for example
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Function Value returned
Abs Absolute value
Asc ASCII or ANSI code of a character
Chr Character corresponding to a given ASCII or ANSI code
Cos Cosine of an angle
Date Current date as a text string
Format Date or number converted to a text string
Left Selected left side of a text string
Len Number of characters in a text string
Mid Selected portion of a text string
Now Current time and date
Right Selected right end of a text string
Rnd Random number
Sin Sine of an angle
Sqr Square root of a number
Str Number converted to a text string
Time Current time as a text string
Timer Number of seconds elapsed since midnight
Val Numeric value of a given text string

36. Visual Basic Symbolic Constants
Functions and objects always require data arguments
that affect their operation and return values you want
to read and interpret. These arguments and values
are constant numerical data and difficult to interpret
based on just the numerical value. To make these
constants more understandable, Visual Basic assigns
names to the most widely used values, these are
called
symbolic constants. You can find such constants
here.
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37. MsgBox Arguments Constants
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Constant Value Description
vbOKOnly 0 OK button only (default)
vbOKCancel 1 OK and Cancel buttons.
vbAbortRetryIgnore 2 Abort, Retry, and Ignore buttons.
vbYesNoCancel 3 Yes, No, and Cancel buttons.
vbYesNo 4 Yes and No buttons.
vbRetryCancel 5 Retry and Cancel buttons.
vbCritical 16 Critical message.
vbQuestion 32 Warning query.
vbExclamation 48 Warning message.
vbInformation 64 Information message.
vbDefaultButton1 0 First button is default (default)
vbDefaultButton2 256 Second button is default.
vbDefaultButton3 512 Third button is default.
vbApplicationModal 0 Application modal message box
vbSystemModal 4096 System modal message box.

38. Example: Temperature conversion
The Fahrenheit temperature is converted into Celsius by
the following formula
The interface should look like shown here
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9
5
*)32F(C 

39. Creating File for Editing
A file is being creating for input, output and as file
editor.
1. Create new project
2. On the form draw a textbox as large as the
size of the form
3. Add from the tool box a COMMON DIALOG
BOX. If it is not there, follow the steps below
a. From PROJECT menu select components
b. Scroll the components to MICROSOFT DIALOG
BOX and check the box .
c. It is now on the toolbox bar.
4. Notice its name which you will use in the
code.
5. Now, use from TOOLS the menu editor to
add (file) and (format) menus.
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40. File Menu
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Use the MNUE EDITOR to write the file
menu components.
The code:
•Exit code
Click on exit in the created file menu,
and start writing the code for ending the
run.
'Make sure user really wants to exit
Dim Response As Integer
Response = MsgBox("Are you sure you
want to exit the note editor?", vbYesNo +
vbCritical + vbDefaultButton2, "Exit Editor")
If Response = vbNo Then
Exit Sub
Else
End
End If

41. • New code
Click on New in the created file menu, and start
writing the code for creating new file.
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'If user wants new file, clear out text
Dim Response As Integer
Response = MsgBox("Are you sure you want to start a new file?",
vbYesNo + vbQuestion, "New File")
If Response = vbYes Then
txtEdit.Text = ""
Else
End If

42. • Save code
Click on Save in the created file menu, and start writing the code for
saving the created file with extension ned (it is arbitrary as long as you
don’t select a known format. The common dialog box here is named
cdlFiles.
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cdlFiles.Filter = "Files (*.ned)|*.ned"
cdlFiles.DefaultExt = "ned"
cdlFiles.DialogTitle = "Save File"
cdlFiles.Flags = cdlOFNOverwritePrompt + cdlOFNPathMustExist
On Error GoTo No_Save
cdlFiles.ShowSave
Open cdlFiles.FileName For Output As #1
Print #1, Val(txtEdit.Text)
Close 1
Exit Sub
No_Save:
Resume ExitLine
ExitLine:
Exit Sub