1. Visual Basic Statements

2. Relational Operators Equal  = Less than  < Greater than  >
Not equal  <>
Less than or equal  <=
Greater than or equal  >=

3. Logical Expressions Let A = x^2 -50 & B = x *(x – 70) A < B
True if A is less than B
False if A is not less than B
A > B
A <> B
True if A is not equal to B
False if A is equal to B
A <= B; A >= B; A = B

4. Logical Expressions String comparisons Equality
FirstName = ”Allama”
SecondName = “Muhammad”
LastName = “Iqbal”
Equality
If FirstName=LastName Then…
If LastName <> SecondName Then...
Inequality (Alphabetic ordering)
AFlag = FirstName > Last Name
Same as AFlag = True

5. Logical Expressions String comparisons Less than  Comes before
Greater than  Comes after
Uppercase precedes lower case
Blank spaces precede nonblank characters
Shorter string precedes longer string
Car precedes Cart

6. Logical Operators Not This  Not This And That  And
This, That Or Both  Or
Either This or That  Xor
A Equivalent to B  Eqv
A Implies B  Imp

7. Not A Not A X=3 Y=5 W = X > Y Z = Not X>Y W = False Z = True

8. And A B A And B False True (X > 10) And (X < 20)
is True only when
10 < X <20

9. Or A B A Or B False True (X > 10) Or (X < 20)
will always be True
(X < 10) Or (X > 20)
will be False when
10 ≤ X ≤ 20

10. Xor (Exclusive Or) A B A Xor B False True (X > 10) Xor (X < 20)
will be False only when
11 ≤ X ≤ 19
(X < 10) Xor (X > 20)
will be False when
10 ≤ X ≤ 20

11. Equivalent A B
A Eqv B
False
True

12. Implies A B
A Imp B
False
True

13. If…Then…End If If expression Then End If Statement(s) True Expression
False

14. If…Then…Else…End If Else If expression Then End If Statement(s) I
Statement(s) II
End If
Expression
Statement(s) I
True
False
Statement(s) II

15. Solution of Quadratic Equation
Private Sub Command1_Click()
Dim A As Integer, B As Integer, C As Integer
Dim D As Single, X As Single, Y As Single
Dim Ans1 As String, Ans2 As String
Dim X1 As Single, X2 As Single
‘ Read Coefficients of the quadratic equation
A = Val(Text1.Text) 'Coefficient of x^2
B = Val(Text2.Text) 'Coefficient of x
C = Val(Text3.Text) 'Constant
‘ Evaluate Discriminant as D
D = B ^ * A * C

16. Solution of Quadratic Equation
If D >= 0 Then
' Roots are real. Equal or unequal
X1 = ( -B + Sqr(D) ) / (2 * A)
X2 = ( -B - Sqr(D) ) / (2 * A)
Ans1 = Str(X1)
Ans2 = Str(X2)
Else
' Roots are complex. Just need the absolute value of the imag. part
X =Abs( Sqr(Abs(D)) / (2 * A))
Y = -B / (2 * A)
Ans1 = Str(Y) & " + i " & Str(X)
Ans2 = Str(Y) & " - i " & Str(X)
End If

17. Solution of Quadratic Equation
Text4.Text = Ans1
Text5.Text = Ans2
End Sub
Assuming that 5 text boxes are created.
Text1Text3 are used to input A, B & C
Text4 & Text5 are used to display answers

18. If…Then…Else If…Else…End If
If expressionA Then
Statement set A
Else If expressionB
Statement Set B
Else If expressionC Then .
Else
Statement Set N
End If

19. If…Then…Else If…Else…End If
False
False
Expression A
Expression B
Expression k
False
True
True
True
Statement Set A
Statement Set B
Statement Set k
Statement Set N

20. Use of If…Then…Else If…
D = B ^ * A * C
If D < 0 Then
Message = "Roots are complex"
ElseIf D = 0 Then
Message = "Roots are real & repeated"
ElseIf D > 0 Then
Message = "Roots are real & distinct"
End If

21. Select Case . Select Case expression Case value set 1 Statement Set 1
Case Else
Statement Set N
End Select
List separated by commas
Values; 1, 3, 5
String(s); “a”, “5”
Range using To
Numbers; 6 To 8
String; “A” To “Z” , “0” To “9”
Logical expression using Is
Numbers: Is >= 9
String: Is < “h”
Not necessary

22. Using Select Case D = B ^ 2 - 4 * A * C n = Sgn(D) Select Case n
Message = "Complex roots"
Case 0
Message = "Real repeated roots"
Case 1
Message = "Real distinct roots"
End Select

23. Using Select Case D = B ^ 2 - 4 * A * C Select Case D Case Is < 0
Message = "Complex roots"
Case Is = 0
Message = "Real repeated roots"
Case Is > 0
Message = "Real distinct roots"
End Select

24. Using Select Case Dim Character As String Select Case Character
Case "A" To "Z", "a" To "z"
Message = "Character is Alphabet"
Case "0" To "9"
Message = "Character is Numeric"
Case Else
Message = "Character is not Alphanumeric"
End Select

25. Format Library function
Y = Format(x, “formatstring”)
Returns the value of x in a format designated by “formatstring”
Some built-in format functions
Standard
Currency
Percent
Scientific
Long Date
Medium Date

26. Format Examples Y = Format(1450.0365, “Standard”) Y = “1,450.04”
Y = Format( , “Currency”)
Y = “$1,450.04”
Y = Format( , “Percent”)
Y = “3.66%”
Y = Format( , “Scientific”)
Y = “1.45E+03”

27. Format Examples Y = Format(Now, “Long Date”)
Y = “Wednesday, October 1, 2003”
Y = Format(Now, “Medium Date”)
Y = “01-Oct-03”
Y = Format(Now, “hh:mm:ss am/pm”)
Y = “09:07:23 am”

28. Format Examples Y = Format(“CS101”, “@@@@@@@@”) Y = “bbbCS101”
b stands for blank. Or CS101 is right-justified.
Y = Format(“CS101”, “&&&&&&&&”)
Y = “CS101”  Right blanks are truncated
b stands for blank. Or CS101 is left-justified.
CS101

29. File Handling Files are used for large data input/output
Create a .txt file called CarData by using Notepad (or ASCII file using other software) with following contents
“Suzuki”, 3, 4
“Toyota”, 5, 7
“Honda”, 4, 15

30. File Handling Files must be Opened before any read/write operation.
Files must be Closed after any read/write operation
Syntax
Open “CarData” For Input As #138
Opens a file called CarData.txt for read-only and this file will be called #138
The file reference number can be from 1 to 255

31. File Handling Close #138 Input #138, Make, NoOfModels, NoOfColors
Assumes that the 1st line of “CarData.txt” contains 3 values corresponding to the three variables.
Make should be a string variable, while NoOfModels and NoOfColors is a numeric type (Integer etc)
After this Input statement
Make = “Suzuki”
NoOfModels = 3
NoOfColors = 4
Close #138

32. File Handling Dim Make As String, NoOfModels As Integer
Dim NoOfColors As Integer
Open "C:\CarData.txt" For Input As #1
Input #1, Make, NoOfModels, NoOfColors
Open "C:\DataOut.txt" For Output As #2
Write #2, Make, NoOfColors, NoOfModels
Close #1
Close #2

33. File Handling "Suzuki", 3, 4 "Toyota", 5, 7 "Honda", 4, 12
Contents of CarData.txt
Contents of DataOut.txt

34. File Handling Dim Make As String, NoOfModels As Integer
Dim NoOfColors As Integer, FMake As String
Open "c:\CarData.txt" For Input As #1
Open "c:\DataOut.txt" For Output As #2
Input #1, Make, NoOfModels, NoOfColors
FMake = Format(Make,
Write #2, FMake, NoOfColors, NoOfModels
Close #1
Close #2

35. File Handling "Suzuki", 3, 4 "Toyota", 5, 7 "Honda", 4, 12
Contents of CarData.txt
Contents of DataOut.txt

36. File Handling Dim Make As String, NoOfModels As Integer
Dim NoOfColors As Integer, FMake As String
Open "c:\CarData.txt" For Input As #1
Open "c:\DataOut.txt" For Output As #2
Input #1, Make, NoOfModels, NoOfColors
FMake = Format(Make,
Write #2, FMake, NoOfColors, NoOfModels
FMake = Format(Make, "&&&&&&&&")
Close #1
Close #2

37. File Handling "Suzuki", 3, 4 "Toyota", 5, 7 "Honda", 4, 12
Contents of CarData.txt
Contents of DataOut.txt