1. Fundamentals of Programming in Visual Basic
Chapter 3-A
Fundamentals of Programming in Visual Basic
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2. Outline and Objectives
Visual Basic Objects
Visual Basic Events
Numbers
Strings
Input/Output
Built-In Functions
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3. The Initial Visual Basic Screen
Menu bar
Project Explorer
window
Toolbar
Toolbox
Properties
window
Description pane
Form
Project Container window
Form Layout window
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4. Steps to Create a Visual Basic Program
1. Create the interface by placing controls on the form
2. Set properties for the controls and the form
3. Write code for event procedures associated with the controls and the form
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5. Four Useful Visual Basic Controls
Text Boxes
Labels
Command Buttons
Picture Boxes
The icons in the Tool Box represent objects that can be placed on the form.
The four objects discussed today are: text boxes…..
Text Box: you use a text box primarily to get information, referred to as input , from the user
Label is placed next to text box to tell the user what type of information to enter into the to he text box
Command button : The user clicks a command button to initiate an action
Picture Boxes: You use a picture box to display text or graphics
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6. Placing a Text Box on a Form
Double-click on the text box icon in the toolbox to add a text box to your form
Activate the properties window (Press F4)
Set values of properties for text box
Go over resizing and dragging the text box
The first line of the properties window (called the object box) reads “Text1 TextBox” . Text1 is the current name of the textbox.
The two Tab permit you to view the list of properties either alphabetically or grouped by categories..
We discuss four properties :
The Text property determines the words in the text box.
Press Shift+Ctrl+F to move to the first property beginning with
F . Move to the property ForeColor. The foregroung color is the
color of the text.. Click on Palette tab to display a selection of colors.
Highlight the Font property and change it to Italic
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7. Placing a label on a Form
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8. Some Useful Properties of Objects
Name
Caption
Text (for Text Boxes)
BorderStyle
Visible
BackColor
Alignment
Font
Border Style: Setting the BorderStyle to 0-None removes the border from an object
Visible: Setting the property to false hides an object when the program run. The object can be set to reappear with code
BackColor: Specifies the background color for text box, label, picture box or form.. Also specific background color for a command button having Style set to “1-Graphical”
BackStyle: The background of a label is opaque by default. Setting the background style of a label to transparent causes whatever is behind the label remain visible.; the background color of the label essentially becomes “see through”
Font: Two unusual fonts are Symbols and Wingdings> For instance with the windingsfonts , changing the text to % & ‘ and J yields a bell, a book, a candle and a smiling face
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9. Chapter 3 - Visual Basic Schneider
Naming Objects:
Use the Property window to change the Name property of an object
Good programming practice dictates that each object name begins with a three letter prefix that identifies the type of object.
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10. Chapter 3 - Visual Basic Schneider
Naming Objects:
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11. Chapter 3 - Visual Basic Schneider
Naming Objects
An Object Name
Must Start with a letter
Can include numbers and underscore (_)
Cannot include punctuation or spaces
Can be a maximum of 40 characters
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12. Chapter 3 - Visual Basic Schneider
Visual Basic Events
Code is a set of statements that instruct the computer to carry out a task.
Code can be associated with events
When an event occurs, the code associated with that event (called an Event Procedure) is executed.
When a VB program is run, a form and its controls appear on the screen. Normally, nothing happens until the user takes an action, such as clicking a control or pressing the Tab key.
Such an action is called event.
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13. Creating An Event Procedure
Double-click on an object to open a Code window. (The empty default event procedure will appear. Click on the Procedure box if you want to display a different event procedure.)
Write the code for that event procedure.
Object Property Setting
frmWalkthrough Caption Demonstration
txtPhrase Text (blank)
cmdBold Caption Make Phrase Bold
Object Box
Procedure Box: Contains a list of all possible event procedures associated with the text box
Choose txtPhrase_LostFocus()
txtPhrase.Font.Size = 12
End Sub
Choose GotFocus and type: txtPhrase.Font.Size = 8
txtPhrase.Font.Bold = False
Go to command Button and choose cmdBold_Click and type txtPhrase.Font.Bold = True
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14. Example of An Event Procedure
Private Sub objectName_event ( )
statements
End Sub
Private Sub Text2_GotFocus( )
Text2.Font.Size = 12
Text2.Font.Bold = False
Text2.forecolor=vbRed
The word Sub signals the beginning of the event procedure, and also identifies the Object and the event occurring to that object
The word private indicates that the event procedure cannot be invoked by an event from another procedure.
The word Sub means subprogram
Example: the event procedure
private Sub cmdButton_Click ()
txtBox.Text = “”
End Sub
The event clicking cmdButton is different from the event clicking picBox_Click
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15. Chapter 3 - Visual Basic Schneider
More Examples
Private Sub cmdButton_Click( )
txtBox.ForeColor = vbRed
txtBox.Font.Size = 24
txtBox.Text = “Hello”
End Sub
Each color can be identified by a sequence of digits and letter beginning with &H. &HFF& = Red
&HFF00& = Green
&HFF000& = Blue
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16. Exercises: What is wrong??!
A. Private Sub cmdButton_Click( )
frmHi= “Hello”
End Sub
B. Private Sub cmdButton_Click( )
txtOne.ForeColor= “red”
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17. Exercises: What is wrong??!
C. Private Sub cmdButton_Click( )
txtBox.Caption = “Hello”
End Sub
D. Private Sub cmdButton_Click( )
txtOne.MultiLine= True
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18. Chapter 3 - Visual Basic Schneider
Tips
Most Properties can be set or altered at run time with code.
cmdButton.visible = False
The MultiLine property of a text box can only be set from the properties window, also the Name property….
“” surrounds Caption, Name, Font.Name or strings. Not True for vars or numeric constants
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19. Chapter 3 - Visual Basic Schneider
Color Constants
At design time colors are selected from a palette
At run time the eight most common colors can be assigned with the color constants:
vbBlack
vbMagenta
vbRed
vbCyan
vbGreen
vbYellow
vbBlue
vbWhite
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20. Components of Visual Basic Statements
Constants
Variables
Keywords (reserved words)
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21. Chapter 3 - Visual Basic Schneider
Constant
Can NOT change during the execution of a program.
Types of Constants:
numeric constants
string constants
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22. Valid Numeric Constants:
Integer Real number
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23. Invalid Numeric Constants:
14, %
$190.04
&
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24. Arithmetic Operations
Operator Operation Basic expression
^ Exponentiation A ^ B
* Multiplication A * B
/ Division A / B
Addition A + B
Subtraction A - B
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25. Chapter 3 - Visual Basic Schneider
Scientific Notation
10n=
103=1000
10-n=
10-3=0.0001
b.10±r VB Notation
bE±r
1.4 * 10-45
14 * 10 ^-45
1.4E -45
1.4E -44
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26. Chapter 3 - Visual Basic Schneider
String Constants:
A sequence of characters treated as a single item
The characters in a string must be surrounded by double quotes (“ ”)
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27. Valid String Constants
“A rose by any other name”
“9W”
“134.23”
“She said, ‘stop , thief!’ ”
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28. Invalid String Constants
‘Down by the Seashore’
“134.24
“She said, “Stop, thief!””
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29. Chapter 3 - Visual Basic Schneider
Variables
A storage location in main memory whose value can be changed during program execution.
These storage locations can be referred to by their names.
Every variable has three properties: a Name, a Value, and a Data Type.
Types of variables: Numeric and String
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30. Rules for Naming Variables
Must begin with a letter
Must contain only letters, numeric digits, and underscores ( _ )
Can have up to 255 characters
VB is insensitive for uppercase or lowercase
Cannot be a Visual Basic language keyword (for example, Sub, End, False)
VB does not distinguish between uppercase and lowercase letters
Example: numberOfCars, tax_Rate_1994
Let statement assigns values to variables and Print method displays the values of variable
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31. Chapter 3 - Visual Basic Schneider
Valid Variable Names:
timeElapsed
a1b2c3
Var_1 n
celsius
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32. Invalid Variable Names:
maximum/average
1stChoice
square yard
Name?
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33. Chapter 3 - Visual Basic Schneider
Keywords
Words that have predefined meaning to Visual Basic .
Can Not be used as variable names.
Examples:
End - Print
Sub - Let
If -Select
While -Call
The VB editor automatically capitalizes the first letter of reserved word
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34. Chapter 3 - Visual Basic Schneider
Numeric Variables
Used to store numbers
Value is assigned by a statement of the form: numVar = expression
The variable must be on the left and the expression on the right.
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35. Assignment Statement:
The statement var = expr assigns the value of the expression to the variable
tax = 0.02 * (income * dependents)
sum = 2 + x y
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36. Valid Assignment Statements
count = count + 1
num = 5
count = count + num /2
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37. Invalid Assignment Statements
10 = count
count + 1 = count
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38. Chapter 3 - Visual Basic Schneider
String Variables
A string variable stores a string.
The rules for naming string variables are identical to those for naming numeric variables.
When a string variable is first declared, its value is the empty string.
The value of string variable is assigned or altered with Let statements and displayed with Print methods just like the
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39. Visual Basic Print Statement
Print is a method used to display data on the screen or printer.
Can be used to display values of variables or expressions
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40. Examples of Print Statements
Private Sub cmdCompute_Click()
picResults.Print 3 + 2
picResults.Print 3 - 2
picResults.Print “3 * 2”
picResults.Print 3 / 2
picResults.Print 3 ^ 2
picResults.Print 2 * (3 + 4)
End Sub
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41. Examples of Print Statements
speed=3
taxRate=speed+5
total=30
picOutput.Print speed
picOutput.Print taxRate
picOutput.Print “Class average is”; total/3 3 8
Class average is 10
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42. Examples of Print Statements
y = 5
picOutput.Print (x + y) / 2, x / y
Output:
10 3
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43. String Variable Example
Private Sub cmdShow_Click()
picOutput.Cls
phrase = "win or lose that counts."
picOutput.Print "It's not whether you "; phrase
picOutput.Print "It's whether I "; phrase
End Sub
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44. Chapter 3 - Visual Basic Schneider
Concatenation
Two strings can be combined by using the concatenation operation.
The concatenation operator is the ampersand (&) sign.
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45. Example &: is always used to make concatenation
+: makes concatenation when it is used with strings, and as summation with numbers
What about “hi”+5 ???

46. Examples of Concatenation:
strVar1 = “Hello” strVar2 = “World” picOutput.Print strVar1& strVar2
txtBox.Text = “32” & Chr(176) & “ Fahrenheit”
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47. Chr() & Asc() Asc(A) = 65 Asc(B) = 66 Asc(a) = 97 Asc( ) = 176
The characters have numbers associated with them, these values called ANSI values of characters
Chr(65) = A
Chr(66) = B
Chr(97) = a
Chr(176) =
Asc(A) = 65
Asc(B) = 66
Asc(a) = 97
Asc( ) = 176

48. 48

49. Val, Str 23 10 50 Val (“23”) = 23 Val (23) =23 Str (23) =
Val(“Hi”) = 0
Val(“89Hello”) = 89
Val(“89Hi10”) = 89
Str("10") + Str("50") =
Str(“Hello”)  error 23
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50. Declaring Variable Types
Use the Dim statement to declare the type of a variable.
Examples:
Dim number As Integer
Dim flower As String
Dim interestRate As Single
From now on we will declare all variables. Declaring variables is regarded as good programming practice.
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51. Chapter 3 - Visual Basic Schneider
Data Types
Single: a numeric variable that stores real numbers (0 By default)
Integer: a numeric variable that stores integer numbers (from to 32767) (0 By default)
String: a variable that stores a sequence of characters (“”empty string By default)
Boolean: a variable that stores True or False (False By default)
The default data type is a single precision numeric variable
Therefore Number and Number! Are the same
Double precision variable is used to store number with many digits
A single precision variable is accurate to about seven decimal points where double precision is accurate to about 15 decimal points
Is used when a high degree of accuracy is needed.
If you try to assign a real number , the number would be cut off and an integer would be assigned to it.
Declaring variables is regarded as good programming practice
Example: Dim variableName As String
Dim variableName As Single
Type Declaration Tags
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52. Using Text Boxes for Input/Output
The contents of a text box are always a string type.
Numbers can be stored in text boxes as strings.
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53. Using Text Boxes for Input/Output
The contents of a text box should be converted to a number before being assigned to a numeric variable.
Val(txtBox.Text) gives the value of a numeric string as a number
Example: Dim numVar as Single numVar = Val(txtBox.Text)
Function Input Output
Str number string
Val string number
If str is a string representation of a number, then Val(str) is that number. Conversely, if num is a number, then Str(num) is a string representation of the number.
Therefore statements such as
numVar = Val(txtBox.Text)
and
txtBox.Text = Str(numVar)
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54. The contents of a text box is always a string
Numbers types into the text box are stored as strings. Therefore, they should be converted to numbers before being assigned to numeric.

55. Chapter 3 - Visual Basic Schneider
Example
Example 1
xString=“528”
xValue=Val(xString)  xValue=528
Example 2
yValue=428
yString=Str(yValue) yString=“428”
xString
xValue
“528”
528
428
“428”
xValue
xString
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56. Program Documentation
An apostrophe (') is used to indicate that the remainder of the line is a comment. (Comments are ignored by Visual Basic.)
Remarks can appear on a separate line or following a Visual Basic statement.
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