Loops In VB

Do-Loops

The most basic form of loop in Visual Basic is the Do-Loop. Its construct is very simple:

Do
(Code to execute)
Loop

This, quite simply, executes the block of code, and when it reaches Loop, returns to the beginning of the Do Loop and executes the same block of code again. The same block of code will be repeatedly executed until it is told to stop executing. So let's try to apply this to our problem of generating the Fibonacci series:


Dim X As Integer

Dim Y As Integer



Do

Debug.Print X



X = Y + X

Y = X - Y

Loop



And, believe it or not, this code works! Well, sorta. If you try to run this code, it will indeed generate the Fibonacci series; however, it will continually generate and print out the next number infinitely--or, in this case, until it reaches an overflow error. This is known as the problem of the infinite do-loop, one that all programmers will experience, and some quite frequently.

Exit Do

So we clearly need some way to escape from the Do-Loop. You could, of course, simply End the program once you have calculated enough values, but what if you still need to perform tasks after you're done calculating? The answer is to use the Exit Do statement. Whenever your program reaches an Exit Do statement within a loop, it will exit the current loop.

So, let's try a somewhat different approach to the Fibonacci problem. We decide that we want to calculate only eight values of the Fibonacci series, so we'll keep a counter and increment it each time throughout the loop. Then, once the counter reaches eight, we'll exit the loop.


Public Sub Main()

Dim X As Integer

Dim Y As Integer

Dim cnt As Integer 'Our counter.

cnt = 1

Do

Debug.Print X

X = Y + X

Y = X - Y



If cnt >= 8 Then

Exit Do

Else
cnt = cnt + 1

End If

Loop

End Sub

And now we're talking! This program successfully computes and prints out the first eight values of the Fibonacci series.

Do Until

As an alternative approach to nesting an If-Statement inside the loop, and invoking Exit Do once we're done looping, Visual Basic provides a Do Until statement. Its syntax is the following:

Do Until (Expression)
(Code to execute)
Loop

(Expression) can be any legal logical expression that we wish to evaluate to determine whether or not to exit the loop. Each time the program reaches Loop it will evaluate this expression. If the expression is True, it will exit the loop for us, but otherwise it will continue looping.. So let's try rewriting our Fibonacci program to use a Do-Until loop instead of Exit Do.

1.
Public Sub Main()
2.
Dim X As Integer
3.
Dim Y As Integer
4.
Dim cnt As Integer 'Our counter.
5.

6.
cnt = 1
7.

8.
Do Until cnt >= 8
9.
Debug.Print X
10.

11.
X = Y + X
12.
Y = X - Y
13.
cnt = cnt + 1
14.
Loop
15.
End Sub



Here we've replaced the hideous If cnt >= 8 Then ... Else: Exit Do with a very simple Until cnt >= 8. We must, however, still be sure to increment our counter every time through the loop, or else the Until expression will never be True, resulting in an infinite Do Loop.

Do While

In the place of Do Until, you can also use Do While. Its syntax is the following:

Do While (Expression)
(Code to execute)
Loop

(Expression) can be any legal logical expression that we wish to evaluate to determine whether or not to exit the loop. Each time the program reaches Loop it will verify that this expression is True, and if it is False, it will exit the loop for us. Thus, instead of exiting when an expression is True, it now exits only once this expression is false. Let's try rewriting our Fibonacci program to use a Do-While loop instead of a Do-Until loop.

Public Sub Main()

Dim X As Integer

Dim Y As Integer

Dim cnt As Integer 'Our counter.



cnt = 1

Do While cnt < 8

Debug.Print X

X = Y + X

Y = X - Y



cnt = cnt + 1

Loop

End Sub

For-Next Loops

In situations where you merely want to run the loop a predefined number of times, it can become quite tiresome to have to create and manage a counter for each loop, which is why we also have something called a For-Next Loop. This kind of loop allows you to specify a counter, to tell it to count from one number to another each time through the loop, and to exit once the counter has reached its upper limit. The syntax is as follow:
Dim I As Integer

For I = (Integer) To (Integer)
(Code to execute)
Next I

We used the variable name "I" above, as it is the most common name used for For-Loops; however, you can use any variable name you want, so long as the variable is of the type Integer. Now, let's improve our Fibonacci program even further:


Public Sub Main()

Dim X As Integer

Dim Y As Integer

Dim cnt As Integer 'Our counter.



For cnt = 1 To 8

Debug.Print X

X = Y + X

Y = X - Y

Loop

End Sub



In the example above, we first dimensioned cnt as an Integer, and then, in the declaration of the For-Next loop, set its value to 1. Each time through the loop, the value of cnt was incremented by 1 until it reached 8, at which point the loop was executed.

Exit For

As with Do Loops, there is a statement that can be used to exit a For-Next loop, and it is called Exit For. Simply invoke this statement anywhere within a For-Next loop and the current loop will be exited.

Step

By default, the variable used in the declaration of the For-Next loop is incremented by 1 each time through the loop; however, if you want to increment this value by a different amount each time through the loop, you can simply append Step (Integer) to the end of the For-Next loop declaration. If, for instance, we wanted to print out every even number counting backward from 20 to 0, we could do this using the following code:


Dim I As Integer



For I = 20 To 0 Step -2

Debug.Print I

Next I

if, else, and select statements

In VB, the following form is preferred for implementing the If-Then-Else structure (this is the "block", or "multi-line" form of the If statement):

If Then

Else

End If

If the conditional expression is true, the statements between the keywords Then and Else will be executed (and the statements between the keywords Else and End If will be bypassed). If the conditional expression is false, the statements between the keywords Else and End If will be executed (and the statements between the keywords Then and Else will be bypassed). In any case, program control will resume with the statement following End If.

Example:

If sngNumberOfCredits <>

lblStatus = "PART-TIME STUDENT"

dblTuitionAmount = sngNumberOfCredits * 175

Else

lblStatus = "FULL-TIME STUDENT"

dblTuitionAmount = 2000

End If

STYLE TIPS FOR THE BLOCK IF STATEMENT:

(1) Indent the "true" actions 4 spaces from the keyword "If"

(2) Code the keyword "Else" on a separate line, aligned with the keyword "If"

(3) Code the "false" actions 4 spaces from the keyword "Else"

(4) Align the keywords "End If" with the keywords "If" and "Else"

Split a given string into different words

Function SplitString%(TheString$, Delim$, DynArray$())
dim p%, t%
dim sTempString$, tmp$
t% = 0
' Remove trailing blanks
sTempString$ = Trim(TheString$)
' If the last character is the delimiter, remove it
If Right(sTempString$, 1) = Delim$ Then sTempString$ = Left(sTempString$, Len(sTempString$) - 1)
' Add a delimiter to end
sTempString$ = sTempString$ & Delim$
Do
p% = InStr(sTempString$, Delim$)
If p% = 0 Then exit Do
ReDim Preserve DynArray$(t%)
tmp$ = Left(sTempString$, p% - 1)
sTempString$ = Right$(sTempString$, Len(sTempString$) - p%)
DynArray$(t%) = Trim(tmp$)
t% = t% + 1
Loop
' Returns the last availabe index
SplitString% = UBound(DynArray$)
End Function

** Calling procedure example:

' text$ is the string to be splitted
' n= number of words found - 1
' delimiter is ","

Dim Words$()
Text$ = Trim(Text$)
n = SplitString(Text$, ",", Words$())



Return

Calculator Project In VB

The basic layout of the screen is shown in the figure 5. There are two control arrays of buttons one for the digits 0 to 9 and another for operators +, -, /, * and =. The form is given the name ‘calculator’ and its icon property is set to calculator icon. The display label is given the name ‘Readout’ and the caption ‘0.’. The number buttons 0 to 9 are given the same name ‘Number’, their captions and indexes are set as 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively. The operator buttons /, +, X, - and = are given the same name, “Operator” , and their indexes are set as 0, 1, 2, 3 and 4 respy. The ‘%’ button is given the name ‘Percent’, the ‘.’ button is given the name ‘Decimal’, the ‘C’ button is given the name ‘Cancel’ and the ‘CE’ button is given the name ‘CancelEntry’. The codes are entered in the code window as shown in the figure 5a. Save and run the project and check that the calculator functions properly.

Option Explicit
Dim Op1, Op2 ' Previously input operand.
Dim DecimalFlag As Integer ' Decimal point present yet?
Dim NumOps As Integer ' Number of operands.
Dim LastInput ' Indicate type of last keypress event.
Dim OpFlag ' Indicate pending operation.
Dim TempReadout
' Click event procedure for C (cancel) key.
' Reset the display and initializes variables.
Private Sub Cancel_Click()
Readout = Format(0, "0.")
Op1 = 0
Op2 = 0
Form_Load
End Sub
' Click event procedure for CE (cancel entry) key.
Private Sub CancelEntry_Click()
Readout = Format(0, "0.")
DecimalFlag = False
LastInput = "CE"
End Sub
' Click event procedure for decimal point (.) key.
' If last keypress was an operator, initialize
' readout to "0." Otherwise, append a decimal
' point to the display.
Private Sub Decimal_Click()
If LastInput = "NEG" Then
Readout = Format(0, "-0.")
ElseIf LastInput <> "NUMS" Then
Readout = Format(0, "0.")
End If
DecimalFlag = True
LastInput = "NUMS"
End Sub

' Initialization routine for the form.
' Set all variables to initial values.
Private Sub Form_Load()
DecimalFlag = False
NumOps = 0
LastInput = "NONE"
OpFlag = " "
Readout = Format(0, "0.")
'Decimal.Caption = Format(0, ".")
End Sub
' Click event procedure for number keys (0-9).
' Append new number to the number in the display.
Private Sub Number_Click(Index As Integer)
If LastInput <> "NUMS" Then
Readout = Format(0, ".")
DecimalFlag = False
End If
If DecimalFlag Then
Readout = Readout + Number(Index).Caption
Else
Readout = Left(Readout, InStr(Readout, Format(0, ".")) - 1) + Number(Index).Caption + Format(0, ".")
End If
If LastInput = "NEG" Then Readout = "-" & Readout
LastInput = "NUMS"
End Sub
' Click event procedure for operator keys (+, -, x, /, =).
' If the immediately preceeding keypress was part of a
' number, increments NumOps. If one operand is present,
' set Op1. If two are present, set Op1 equal to the
' result of the operation on Op1 and the current
' input string, and display the result.
Private Sub Operator_Click(Index As Integer)
TempReadout = Readout
If LastInput = "NUMS" Then
NumOps = NumOps + 1
End If
Select Case NumOps
Case 0
If Operator(Index).Caption = "-" And LastInput <> "NEG" Then
Readout = "-" & Readout
LastInput = "NEG"
End If
Case 1
Op1 = Readout
If Operator(Index).Caption = "-" And LastInput <> "NUMS" And OpFlag <> "=" Then
Readout = "-"
LastInput = "NEG"
End If
Case 2
Op2 = TempReadout
Select Case OpFlag
Case "+"
Op1 = CDbl(Op1) + CDbl(Op2)
Case "-"
Op1 = CDbl(Op1) - CDbl(Op2)
Case "X"
Op1 = CDbl(Op1) * CDbl(Op2)
Case "/"
If Op2 = 0 Then
MsgBox "Can't divide by zero", 48, "Calculator"
Else
Op1 = CDbl(Op1) / CDbl(Op2)
End If
Case "="
Op1 = CDbl(Op2)
Case "%"
Op1 = CDbl(Op1) * CDbl(Op2)
End Select
Readout = Op1
NumOps = 1
End Select
If LastInput <> "NEG" Then
LastInput = "OPS"
OpFlag = Operator(Index).Caption
End If
End Sub
' Click event procedure for percent key (%).
' Compute and display a percentage of the first operand.
Private Sub Percent_Click()
Readout = Readout / 100
LastInput = "Ops"
OpFlag = "%"
NumOps = NumOps + 1
DecimalFlag = True
End Sub

Progress Bar In VB

Private Sub cmdStart_Click()
' Set minimum and maximum values for progress
ProgressBar1.Min = 1
ProgressBar1.Max = 5000
' Loop 5000 times
For i = 1 To 5000
' Set current value to loop value so progress will show status
ProgressBar1.Value = i
Text1 = CStr(i / 50) + "%completed"
Next i
' Tell user routine is complete
MsgBox "Done", vbInformation, "Complete."
End Sub

TreeView Control In VB

Private Sub Command1_Click()
Dim nodx As Node
Set nodx = TreeView1.Nodes.Add(, , "R", "FoodTypes")
Set nodx = TreeView1.Nodes.Add("R", tvwChild, "Ft", "Fruits")
Set nodx = TreeView1.Nodes.Add("R", tvwChild, "Vg", "Vegetables")
Set nodx = TreeView1.Nodes.Add("R", tvwChild, "Mt", "Meat")
Set nodx = TreeView1.Nodes.Add("R", tvwChild, "Jf", "Juicy Food")
Set nodx = TreeView1.Nodes.Add("R", tvwChild, "Sf", "Salty Snacks")
nodx.EnsureVisible
End Sub

Private Sub Command2_Click()
Set nodx = TreeView1.Nodes.Add("Ft", tvwChild, "Ap", "Apple")
Set nodx = TreeView1.Nodes.Add("Ft", tvwChild, "Or", "Orange")
Set nodx = TreeView1.Nodes.Add("Ft", tvwChild, "Pr", "Pear")
End Sub

Private Sub Command3_Click()
Set nodx = TreeView1.Nodes.Add("Vg", tvwChild, "Bn", "Beans")
Set nodx = TreeView1.Nodes.Add("Vg", tvwChild, "Cr", "Carrot")
Set nodx = TreeView1.Nodes.Add("Vg", tvwChild, "Rd", "Raddish")
End Sub

BubbleSort In VB

Sub BubbleSort(arr As Variant, Optional numEls As Variant, _
Optional descending As Boolean)

Dim value As Variant
Dim index As Long
Dim firstItem As Long
Dim indexLimit As Long, lastSwap As Long

' account for optional arguments
If IsMissing(numEls) Then numEls = UBound(arr)
firstItem = LBound(arr)
lastSwap = numEls

Do
indexLimit = lastSwap - 1
lastSwap = 0
For index = firstItem To indexLimit
value = arr(index)
If (value > arr(index + 1)) Xor descending Then
' if the items are not in order, swap them
arr(index) = arr(index + 1)
arr(index + 1) = value
lastSwap = index
End If
Next
Loop While lastSwap
End Sub

Age Claculator In VB

Private Sub Command1_Click()
Dim mdate As Date
Dim i, j, k As Integer
mdate = Text1.Text
i = DateDiff("yyyy", mdate, Now)
j = DateDiff("m", mdate, Now)
If i > 12 Then
j = (j Mod 12)
If j <> 0 Then
i = i - 1
End If
End If
Label1.Caption = "age is " & i & "years" & j & "months"
End Sub

Login code For VB

Dim i As Integer
Private Sub Command1_Click()
If Text1.Text = "pop" Then
MsgBox "welcome"
Else
i = i + 1
If i = 3 Then
MsgBox "u r try over"
End
Else
MsgBox "wrong pwd"
End If
End If
End Sub
Private Sub Form_Load()
i = 0
End Sub

Transposing a 2d array

Function Array2DTranspose(avValues As Variant) As Variant
Dim lThisCol As Long, lThisRow As Long
Dim lUb2 As Long, lLb2 As Long
Dim lUb1 As Long, lLb1 As Long
Dim avTransposed As Variant

If IsArray(avValues) Then
On Error GoTo ErrFailed
lUb2 = UBound(avValues, 2)
lLb2 = LBound(avValues, 2)
lUb1 = UBound(avValues, 1)
lLb1 = LBound(avValues, 1)

ReDim avTransposed(lLb2 To lUb2, lLb1 To lUb1)
For lThisCol = lLb1 To lUb1
For lThisRow = lLb2 To lUb2
avTransposed(lThisRow, lThisCol) = avValues(lThisCol, lThisRow)
Next
Next
End If

Array2DTranspose = avTransposed
Exit Function

ErrFailed:
Debug.Print err.description
Debug.Assert False
Array2DTranspose = Empty
Exit Function
Resume
End Function

MsgBox In VB

Private Sub Command1_Click()
intresponse = MsgBox("This is vb Critical", vbCritical)
End Sub

Private Sub Command2_Click()
intresponse = MsgBox("This is vb Questation", vbQuestion)

End Sub

Private Sub Command3_Click()
intresponse = MsgBox("This is vb warning", vbExclamation)

End Sub

Private Sub Command4_Click()
intresponse = MsgBox("This is vb Information", vbInformation)
End Sub

Inputbox In VB

Private Sub Command1_Click()
stranswer = InputBox("what is ur name", "get name")
If (stranswer = "pop") Then
MsgBox "hello " + stranswer
Else
MsgBox stranswer + " Shut up!"
End If
End Sub

Pay Slip In VB

Dim bs As Integer
Dim da As Integer
Dim hra As Integer
Dim net As Integer
Private Sub Command1_Click()
bs = Text3.Text
If bs >= 5000 And bs < 7500 Then
hra = (10 * bs) / 100
da = (bs * 15) / 100
Else
If bs >= 7500 Then
hra = (20 * bs) / 100
da = (20 * bs) / 100
End If
End If
net = bs + da + hra
Text4.Text = da
Text5.Text = hra
Text7.Text = net
'End If
End Sub

Fibonanci Series In VB

Dim i, f1, f2, f3, n As Integer


Private Sub Command1_Click()
n = Text1.Text
i = 3
While (i <= n)
f3 = f1 + f2
f1 = f2
f2 = f3
Next
Print f3
End Sub

Basic Salary Program in VB

Private Sub Command1_Click()
da = Text2.Text * 5 / 100
hra = Text2.Text * 7 / 100
tax = Text2.Text * 2 / 100
net = Int(Text2.Text) + Int(da) + Int(hra) - Int(tax)

Label4.Caption = "The DA is " & da & "/-"
Label5.Caption = "The HRA is " & hra & "/-"
Label6.Caption = "The TAX is " & tax & "/-"
Label3.Caption = "The Netsal is " & net & "/- Rs Only."
End Sub

Arithmatic Operation In VB

Dim a, b, c As Integer
Private Sub Command1_Click()
a = Text1.Text
b = Text2.Text
c = Val(a) + Val(b)
Label2.Caption = c
End Sub

Private Sub Command2_Click()
a = Text1.Text
b = Text2.Text
c = a - b
Label2.Caption = c
End Sub

Private Sub Command3_Click()
a = Text1.Text
b = Text2.Text
c = a * b
Label2.Caption = c
End Sub

Private Sub Command4_Click()
a = Text1.Text
b = Text2.Text
c = a / b
Label2.Caption = c
End Sub

Private Sub Command5_Click()
Text1.Text = ""
Text2.Text = ""
Label2.Caption = ""
End Sub

Private Sub Command6_Click()
End
End Sub

Area Of Circle In VB

Dim r, b, pi As Integer
'code for calculate button
Private Sub Command1_Click()
pi = 3.14
r = Text1.Text
b = pi * (r * r)
Label2.Caption = "The Area is " & b

End Sub

'code for exit button
Private Sub Command2_Click()
End
End Sub
'clear button
Private Sub Command3_Click()
Text1.Text = ""
Label2.Caption = ""
End Sub