Interfacing Parallel Port using Visual Basic (Basic Queueing System)

A tutorial on Parallel port interfacing and programming for beginners. This tutorial covers both hardware and software aspects about programming the parallel port. It also includes a sample schematic and test program using Visual Basic 2005.. I'll be posting the circuit and the codes soon after you request.. Just post a comment or mail me.

Allowing only LETTERS in a textbox

Private Sub TextBox3_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox3.KeyPress

If Asc(e.KeyChar) < 65 Or Asc(e.KeyChar) > 90 AndAlso Asc(e.KeyChar) < 97 Or Asc(e.KeyChar) > 122 Then

MessageBox.Show("Only Letters")

e.Handled = True

ElseIf Asc(e.KeyChar) = 8 Then
e.Handled = False

End If
End Sub

Allow only LETTERS and Backspace in a textbox

Private Sub TextBox4_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox4.KeyPress

If (e.KeyChar >= "a" And e.KeyChar = "A" And e.KeyChar
e.Handled = False

Else
e.Handled = True
MessageBox.Show("Only Letters")

End If
End Sub

Allow NUMBERS, BACKSPACE and a DOT in a textbox

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) _
Handles TextBox1.KeyPress

'There are a couple scenerios this code is looking for. One is checking for the Decimal period "."
'and whether it exists in the textbox already. The other is seeing if the keypress was a Number and
'Control based key.


If e.KeyChar = "." Then


'If a value higher than -1 is returned, it means there IS a existing decimal point’


If TextBox1.Text.IndexOf(".") > -1 Then

'This says that I already dealt with the _KeyPress event so do not do anything else with this event.


e.Handled = True

End If

'Remember you want numbers to get through and the Control keys like “Backspace”

ElseIf Char.IsNumber(e.KeyChar) = False AndAlso Char.IsControl(e.KeyChar) = False Then

'This says that I already dealt with the _KeyPress event so do not do anything else with this event.

e.Handled = True

End If
End Sub

Date and Time Difference user interface:

here is the CODE:

Public Class frmDateandTimeDifference

Private Sub btnGettheDifference_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGettheDifference.Click

Dim Diff1, Diff2, Diff3 As Long

Select Case cboSelect.SelectedIndex

Case 0
Diff1 = DateDiff(DateInterval.Year, dtpStartDate.Value, dtpEndDate.Value)
Diff2 = DateDiff(DateInterval.Month, dtpStartDate.Value, dtpEndDate.Value)
Diff3 = DateDiff(DateInterval.Day, dtpStartDate.Value, dtpEndDate.Value)
lblOutput.Text = Diff1 & " Year/s " & Diff2 & " Month/s " & Diff3 & " Day/s "

Case 1
Diff1 = DateDiff(DateInterval.Hour, dtpStartTime.Value, dtpEndTime.Value)
Diff2 = DateDiff(DateInterval.Minute, dtpStartTime.Value, dtpEndTime.Value)
Diff3 = DateDiff(DateInterval.Second, dtpStartTime.Value, dtpEndTime.Value)
lblOutput.Text = Diff1 & " Hour/s " & Diff2 & " Minute/s " & Diff3 & " Second /s "

End Select
End Sub

Private Sub frmDateandTimeDifference_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

cboSelect.Items.Add("Year, Month, Day")
cboSelect.Items.Add("Hour, Minute, Second")
End Sub

Private Sub Label6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label6.Click

Me.Close()
End Sub

End Class

**Run and Save the program.....

Proper Case

1. Proper Case user interface:



2. Code....

Public Class frmProperCase

Private Sub btnConvert_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConvert.Click

txtProperCase.Text = Microsoft.VisualBasic.StrConv(txtInput.Text, VbStrConv.ProperCase)
End Sub

Private Sub Label2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label2.Click

Me.Close()
End Sub

End Class

3. Save and RUN the program...

Character Count

1. Character Count user interface:



2. The Code....

Public Class frmCharacterCount

Private Sub btnClickHereToCount_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClickHereToCount.Click

Dim length, x, count As Integer
Dim letter As String

length = Microsoft.VisualBasic.Len(txtPhrase.Text)

For x = 1 To length

letter = Microsoft.VisualBasic.Mid(txtPhrase.Text, x, 1)

If Microsoft.VisualBasic.StrComp(letter, txtcharacter.Text, CompareMethod.Text) = 0 Then

count = count + 1
End If

Next

lblOutput.Text = "There are " & count & " " & txtcharacter.Text & " in the Phrase."
End Sub

Private Sub exit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles exit.Click

Me.Close()
End Sub
End Class

3. Save and RUN the program...