1. Fundamentals of Programming in Visual Basic
Chapter 3
Fundamentals of Programming in Visual Basic
Chapter 3 - Visual Basic Schneider
hhhhhhh

2. Outline and Objectives
Visual Basic Objects
Visual Basic Events
Numbers
Strings
Input/Output
Built-In Functions
Chapter 3 - Visual Basic Schneider
hhhhhhh

3. The Initial Visual Basic Screen
Menu bar
Project Explorer
window
Toolbar
Toolbox
Properties
window
Description pane
Form
Project Container window
Form Layout window
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

7. Placing a label on a Form
Chapter 3 - Visual Basic Schneider
hhhhhhh

8. Some Useful Properties of Objects
Name
Caption
Text (for Text Boxes)
BorderStyle
Visible
BackColor
Alignment
Font
ForeColor
MultiLine
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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

10. Chapter 3 - Visual Basic Schneider
Naming Objects:
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

14. Example of An Event Procedure
Private Sub objectName_event ( )
statements
End Sub
Private Sub Text2_GotFocus( )
Text2.FontSize = 12
Text2.FontBold = 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
Chapter 3 - Visual Basic Schneider
hhhhhhh

15. Chapter 3 - Visual Basic Schneider
More Examples
Private Sub cmdButton_Click( )
txtBox.ForeColor = vbRed
txtBox.FontSize = 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
Chapter 3 - Visual Basic Schneider
hhhhhhh

16. Exercises: What is wrong??!
A. Private Sub cmdButton_Click( )
frmHi = "Hello"
End Sub
B. Private Sub cmdButton_Click( )
txtOne.ForeColor = "red"
Chapter 3 - Visual Basic Schneider

17. Exercises: What is wrong??!
C. Private Sub cmdButton_Click( )
txtBox.Caption = "Hello"
End Sub
D. Private Sub cmdButton_Click( )
txtOne.MultiLine = True
Chapter 3 - Visual Basic Schneider

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, Font.Name or strings. Not True for numeric variables or numeric constants
Chapter 3 - Visual Basic Schneider

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
Chapter 3 - Visual Basic Schneider

20. Components of Visual Basic Statements
Constants
Variables
Keywords (reserved words)
Chapter 3 - Visual Basic Schneider
hhhhhhh

21. Chapter 3 - Visual Basic Schneider
Constant
Can NOT change during the execution of a program.
Types of Constants:
numeric constants
string constants
Chapter 3 - Visual Basic Schneider
hhhhhhh

22. Valid Numeric Constants:
Integer Real number
Chapter 3 - Visual Basic Schneider
hhhhhhh

23. Invalid Numeric Constants:
14, %
$190.04
&
Chapter 3 - Visual Basic Schneider
hhhhhhh

24. Arithmetic Operations ( Priorities )
Operator Operation Basic expression
^ Exponentiation A ^ B
* Multiplication A * B
/ Division A / B
Addition A + B
Subtraction A - B
Chapter 3 - Visual Basic Schneider
hhhhhhh

25. Chapter 3 - Visual Basic Schneider
Scientific Notation
103=1000
10n=
10-3=0.001
10-n=
Mathematical Notation
b.10±r
Visual Basic Notation
bE±r
1.4 * 10^-45
14 * 10 ^46
 E-45
 E+47
Chapter 3 - Visual Basic Schneider

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 (“ ”)
Chapter 3 - Visual Basic Schneider
hhhhhhh 26

27. Valid String Constants
“A rose by any other name”
“9W”
“134.23”
“She said, ‘stop , thief!’ ”
Chapter 3 - Visual Basic Schneider
hhhhhhh 27

28. Invalid String Constants
‘Down by the Seashore’
“134.24
“She said, “Stop, thief!””
Chapter 3 - Visual Basic Schneider
hhhhhhh 28

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

31. Chapter 3 - Visual Basic Schneider
Valid Variable Names:
timeElapsed
a1b2c3
Var_1 n
celsius
Chapter 3 - Visual Basic Schneider
hhhhhhh 31

32. Invalid Variable Names:
maximum/average
1stChoice
square yard
Name?
Chapter 3 - Visual Basic Schneider
hhhhhhh 32

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

36. Valid Assignment Statements
count = count + 1
num = 5
count = count + num /2
Chapter 3 - Visual Basic Schneider
hhhhhhh

37. Invalid Assignment Statements
10 = count
count + 1 = count
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh 38

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

42. Examples of Print Statements
y = 5
picOutput.Print (x + y) / 2 , x / y
Output:
10 3
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

44. Chapter 3 - Visual Basic Schneider
Concatenation
Two strings can be combined by using the concatenation operation.
The concatenation operator is the ampersand (&) sign.
Chapter 3 - Visual Basic Schneider
hhhhhhh

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”
Chapter 3 - Visual Basic Schneider
hhhhhhh

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 (“24”) = 24 Val (24) = 24 Str (23) =
Val(“Hi”) = 0
Val(“89Hello”) = 89
Val(“89Hi10”) = 89
Str("10") + Str("50") =
Str(“Hello”)  error 23
One space

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

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
Chapter 3 - Visual Basic Schneider
hhhhhhh

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

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)
Chapter 3 - Visual Basic Schneider
hhhhhhh

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”
yValue
yString
Chapter 3 - Visual Basic Schneider
hhhhhhh

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.
Chapter 3 - Visual Basic Schneider
hhhhhhh

57. The KeyPress Event Procedure
Private Sub txtCharacter_KeyPress(KeyAscii As Integer)
txtCharacter.Text = ""
picOutput.Cls
picOutput.Print Chr(KeyAscii); " has ANSI value"; KeyAscii
End Sub
Chapter 3 - Visual Basic Schneider
hhhhhhh

58. Reading Data from Files
1. Choose a number to be the reference number for the file
2. Execute an Open statement
3. Read the data sequentially using Input # statements
4. Close the file
1. The name of the file: follows the same rules for naming program files.
Use invest.bas and invest.dat
2. The mode in which the file is to be used , can be output, input, append .
Output: indicates data is written to the file from the program
input: the contents of the file are being read into the program
append :allows new records to be added to an existing file.
A butter is a reserved part of the primary storage unit used a s temporary storage area for the data that is being written or read from a file
Chapter 3 - Visual Basic Schneider
hhhhhhh

59. Example of Reading from a File:
Open the file
Open “C:\Temp\DATA.TXT” For Input As #1
Input #1, num1
Input #1, num2
picOutput.Print num1+num2  7
Close #1
Reference number
Read the data and assign it to num1
Data.txt
A file can have either one item per line or many items (separated by commas) can be listed on the same line
the items of data will be assigned to variables one at the time in the order they appear in the file.
1. Choose a number from 1 to 255 to be the reference number for the file
2. Open the file for input
3. Read items of data in order, one at the time, from the file with Input sattement
Show Examples: Path is C;\F98 CSE181\Examples\Ch3\Data.txt
The response typed into an input box is treated as a single string value, no matter what is typed. Quotation marks are not needed, and if included, are considered as part of the string.
Numeric data typed into n input box should be converted to a number with Val before it is assigned to a numeric variable or used in calculation.
Close the file 3 4
Chapter 3 - Visual Basic Schneider
hhhhhhh

60. Example of Reading from a File:
Open “C:\Temp\DATA.TXT” For Input As #1
Input #1, num1, num2
picOutput.Print num1+num2  7
Close #1
Data.txt 3 4
math.txt
Example #1: create a file named Student.dat
Prepare the file to receive data
If a file already exists, it is destroyed and a new file is created.
Associated with the file Student.date with buffer #1. As long as the file is open. Buffer #1 is used temporarily before the data is written to the file on disk
Other statement in the program use this number to identify the file..
2 , 4 , 5 8 5 6
Chapter 3 - Visual Basic Schneider
hhhhhhh

61. Reading Data from Files
Files can be also used for output rather than input. More about files will be discussed in chapter 8 and 9.
Chapter 3 - Visual Basic Schneider
hhhhhhh

62. Chapter 3 - Visual Basic Schneider
Input Dialog Box
An input dialog box can be used to obtain a single item of input from the user
Presents a window (dialog box) requesting input
Syntax:
stringVar = InputBox(prompt, title)
Note: The type of inputBox is string type
After users types in a response into the rectangle at the bottom of the screen and press Enter, the response is assigned to the string variable.
Normally, text box is used to obtain input, sometimes we want just one piece of input and would rather not have a text box and label stay on the screen for ever.
Example
Chapter 3 - Visual Basic Schneider
hhhhhhh

63. Using Message Dialog Box for Output
The message dialog box is used to present a pop-up window containing information for the user
Syntax:
MsgBox prompt , , title
Chapter 3 - Visual Basic Schneider
hhhhhhh

64. Example of a Message Dialog Box
MsgBox "CS116", , "Visual Basic"
Stays on the
screen until the
user presses OK
hhhhhhh 64

65. Example of a Message Dialog Box
MsgBox "CS116"

66. Example

67. Formatting the Output:
Create easily readable output
In the Print method, the spacing of the output is controlled by the following devices:
semicolon
comma
Tab function
Chapter 3 - Visual Basic Schneider
hhhhhhh

68. Chapter 3 - Visual Basic Schneider
Semicolons
The next value output is placed in the next column position.
Example:
picOutput.Print “Patrick” ; ”Jon”
Output:
PatrickJon
Chapter 3 - Visual Basic Schneider
hhhhhhh

69. Chapter 3 - Visual Basic Schneider
Example of Semicolon
picOutput.Print “Patrick” ; “ Jon”
Output Screen:
Patrick Jon
One Space here
One Space here
Chapter 3 - Visual Basic Schneider
hhhhhhh

70. Chapter 3 - Visual Basic Schneider
Example of Semicolon
picOutput.Print 100 ; -200 ; 300
Output Screen:
Two spaces
One space
Chapter 3 - Visual Basic Schneider
hhhhhhh

71. Chapter 3 - Visual Basic Schneider
Commas
A comma in a Print method causes the next value output to be placed in the next available print zone.
Each print zone is 14 positions wide.
Note : The Font setting for Picture Boxes and Form is the font Courier New.
Chapter 3 - Visual Basic Schneider
hhhhhhh

72. Chapter 3 - Visual Basic Schneider
Using Commas
Example:
picOutput.Print “SEE”, ”YOU”, ”SOON”
Output Screen:
SEE YOU SOON
See in column 1 Y in column 15 and S in column 29
Column 29
Column 15
Column 1
Chapter 3 - Visual Basic Schneider
hhhhhhh

73. Chapter 3 - Visual Basic Schneider
Using Commas
Example:
picOutput.Print “abc123def456ghi”, ”whatever”
Output Screen:
abc123def456ghi whatever
See in column 1 Y in column 15 and S in column 29
Column 29
Column 15
Column 1
Chapter 3 - Visual Basic Schneider
hhhhhhh

74. Chapter 3 - Visual Basic Schneider
Using Commas
A print zone can be skipped by typing consecutive commas
Example:
picOutput.Print “HOURLY”, , “PAY”
Output Screen:
HOURLY PAY
Example 3.5.5
Column 29
Chapter 3 - Visual Basic Schneider
hhhhhhh

75. Cls: clears the form of all text
PicBox.Cls: clears the PicBox of all text

76. Private Sub cmdAdd_Click()
picoutput.Print " "
picoutput.Print 10; 20;
picoutput.Print -10, 30,
picoutput.Print
picoutput.Print 15; ; 6
picoutput.Print "Hello"; "hi";
picoutput.Print "12345", "12"
End Sub
;  in the next position column position
,  in the next available print zone
picOutput.Print  moves the cursor to the beginning of the next line

77. Chapter 3 - Visual Basic Schneider
Tab Function
Specifies the column where output will start
Use only semicolons with the Tab function
Can only be used to advance the print position (cannot move backwards)
Chapter 3 - Visual Basic Schneider
hhhhhhh

78. Example of Tab Function
picOutput.Print Tab(3); “Hi there!” ; Tab(25) ;“Bye!”
Output Screen:
Hi there! Bye!
Example 3.5.6
Organizes data into columns of a table
Column 25
Column 3
Chapter 3 - Visual Basic Schneider
hhhhhhh

79. Example of Tab Function
picOutput.Print Tab(3); “Hi there!” ; Tab(5) ;“Bye!”
Because column 5 is already occupied by the previous string, the output will be at the next line
Output Screen:
Hi there!
Bye!
Example 3.5.6
Organizes data into columns of a table
Column 3
Column 5
Chapter 3 - Visual Basic Schneider
hhhhhhh

80. Tab

81. Chapter 3 - Visual Basic Schneider
Built-In Functions
Take one or more input values and return an output value
A means provided by Visual Basic for carrying out small, common tasks
Types of Built-In functions
Numeric functions (manipulate numbers)
String functions (manipulate strings)
Chapter 3 - Visual Basic Schneider
hhhhhhh

82. Chapter 3 - Visual Basic Schneider
Numeric Functions
Example for Int function and Sqr function
Example : rounds a positive number to the nearest integer..
To round a number t two decimal places
r = Int (100*n + 0.5) / 100
Chapter 3 - Visual Basic Schneider
hhhhhhh

83. Example of Numeric Functions
Private Sub cmdEvaluate_Click()
Dim n As Single, root As Single
n = 6.76
root = Sqr(n)
picResults.Print root; Int(n); Round(n,1)
End Sub
Output:
Chapter 3 - Visual Basic Schneider
hhhhhhh

85. Something about Round with number 5
123.8
12.4 4 4 5
23.6
Note that to round a number that is followed by number 5 and nothing after number 5, if it is odd make the round, if it is even number don’t round

86. Commonly-Used String Functions
Function: Left(“Penguin”, 4)
Purpose: Returns the number of characters specified, starting at the beginning of the string
Peng
Chapter 3 - Visual Basic Schneider
hhhhhhh

87. Commonly-Used String Functions
Function: Right(“Gotham City”, 4)
Purpose: Returns the number of characters specified from the end of the string
City
Chapter 3 - Visual Basic Schneider
hhhhhhh

88. Commonly-Used String Functions
Function: Mid(“Commissioner”, 4, 3)
Purpose: Returns the substring starting at the position indicated by the first number and continuing for the length specified by the second number
mis
Chapter 3 - Visual Basic Schneider
hhhhhhh

89. Commonly-Used String Functions
Function: UCase(“Yes”)
Purpose: Converts any lowercase letters in a string to uppercase
YES
Go over Example 6 page 121
Chapter 3 - Visual Basic Schneider
hhhhhhh

90. String-Related Numeric Functions
Function: InStr(“John Smith”, “m”)
Purpose: Searches for the first occurrence of one string in another and gives the position at which the string is found 7
Chapter 3 - Visual Basic Schneider
hhhhhhh

91. String-Related Numeric Function
Function: Len(“John Smith”)
Purpose: Returns the number of characters in the string. 10
Is 10
Chapter 3 - Visual Basic Schneider
hhhhhhh

92. Strings and string Functions examples

93. Example

94. Example

95. Chapter 3 - Visual Basic Schneider
Format Functions
The format functions provide detailed control of how numbers, dates, and strings are displayed.
Examples
FormatNumber ( , 1) ,345.7
FormatCurrency ( , 2) $12,345.68
FormatPercent (.185, 2) %
FormatNumber (1 + Sqr(2), 3)
Numbers can be made to line up uniformly and be displayed with dollar signs, commas and a specified number of decimal places. Dates can be converted
to a long or medium form. Strings can be right justified.
Chapter 3 - Visual Basic Schneider
hhhhhhh

96. Chapter 3 - Visual Basic Schneider
Format Function
Format (expr,
Purpose: The value of this function is the value of expr right justified in a field of n spaces, where n is the number symbols.
If num is number , numeric expression , or a string representation of a number, and fmt is a s string of symbols, then Format (num,fmt) is asserting of character with the number right justified in a field of n spaces.
If num is any string,produced by a Format function , then the value of Format (num,fmt) contains the string right-justified in a field of n spaces.
Chapter 3 - Visual Basic Schneider
hhhhhhh

97. Chapter 3 - Visual Basic Schneider
Format Examples
Format(12345,
Format(123,
Format(“123.4”,
Chapter 3 - Visual Basic Schneider
hhhhhhh

98. Chapter 3 - Visual Basic Schneider
Examples
Chapter 3 - Visual Basic Schneider
hhhhhhh

99. Chapter 3 - Visual Basic Schneider
Examples
Chapter 3 - Visual Basic Schneider
hhhhhhh

100. Chapter 3 - Visual Basic Schneider
Examples
Chapter 3 - Visual Basic Schneider
hhhhhhh

101. FormatDateTime Example
Picture1.Print FormatDateTime(" ", vbLongDate)
Picture1.Print FormatDateTime(" ", vbShortDate)
String Value:
Sunday, September20, 1998
09-Sep-98
Chapter 3 - Visual Basic Schneider
hhhhhhh

102. Chapter 3 - Visual Basic Schneider
Rnd Function
Returns a random number from 0 to 1.
(excluding 1).
Example:
picBox.Print Rnd
Output: Displays a random number from 0 to 1 (0 included and 1 excluded).
picBox.Print Rnd +5
Output: Displays a random number from 5 to 6 (5 included and 6 excluded).
Chapter 3 - Visual Basic Schneider
hhhhhhh

103. Chapter 3 - Visual Basic Schneider
Rnd Function
Example:
picBox.Print Int(Rnd)
Output: Displays 0.
picBox.Print Int(Rnd +5)
Output: Displays 5.
picBox.Print Int(Rnd) +5
Chapter 3 - Visual Basic Schneider
hhhhhhh

104. Chapter 3 - Visual Basic Schneider
Rnd Function
Example:
picBox.Print Int(5*Rnd)
Output: Displays a random Integer from 0 to 4 (0 and 4 included). OR
Output: Displays a random Integer from 0 to 5 (0 included and 5 excluded)
picBox.Print Int(5*Rnd) +2
Output: Displays a random Integer from 2 to 6 (2 and 6 included).
Chapter 3 - Visual Basic Schneider
hhhhhhh

105. Exercise: Revision
What will be dsiplayed in the picOutput when the user double click (click 2 times) on the command button cmdExample

106. Exercises:
Position the location of the form at run time  Form layout windows
To open a file called “data.txt” located in C:\VB folder you must write
 Open “C:\VB\data.txt” for input as #1
Which of the following statement assign the content of the input box to a numeric variable X
X = Val(InputBox(“Enter the number”))

107. What is the output of the following code?
Dim s as integer, n as integer
Open “C:\user\temp\data.txt” for Input as #1
Input #1,n
s=s+n
close #1
print “s=”;s
output: s= 60
data.txt 10 20 30

108. what is output of the following code?
Dim n as integer
Open “D:\user\temp\data.txt” for Input as #1
Input #1,n
Close #1
Print “n = ”; n
Output:
n = 20
data.txt 10 20 30

109. what is output of the following code?
Dim n as integer
Open “D:\user\temp\data.txt” for Input as #1
Input #1,n
Close #1
Print “n = ”; n
Output:
n = 10
data.txt 10 20 30

110. Syntax Errors (Compile Errors)
Grammatical errors, such as misspelling, are called syntax error. Syntax error is encountered during compilation (by Complier)
picBox.Primt 3
9W = 5
picBox.Print 2-
If x >  missing Then
x = x+1
End If

111. Run-time errors
Errors that occur while a program is running are called run-time errors
Division by zero
File not found

112. Example

113. Logical errors
Occurs when a program dose not perform the way it was intended
A program with a logic error is a valid program in the language, though it does not behave as intended.
Average = num1 + num2 / 2

114. Debugging
The process of correcting errors that are found.

115. Chapter 3 - Visual Basic - Schneider
Reference
Chapter 3 - Visual Basic - Schneider