You learn the core logic of building desktop applications, including forms, controls, and event handling.
Dim firstNumber As Double Dim secondNumber As Double Dim activeOperation As String Dim isNewNumber As Boolean Private Sub Form_Load() txtDisplay.Text = "0" isNewNumber = True End Sub ' Handles clicks for all 10 digit buttons via Control Array Private Sub cmdNumber_Click(Index As Integer) If isNewNumber Then txtDisplay.Text = CStr(Index) isNewNumber = False Else txtDisplay.Text = txtDisplay.Text & CStr(Index) End If End Sub Private Sub cmdAdd_Click() SelectOperation "+" End Sub Private Sub cmdSubtract_Click() SelectOperation "-" End Sub Private Sub cmdMultiply_Click() SelectOperation "*" End Sub Private Sub cmdDivide_Click() SelectOperation "/" End Sub Private Sub SelectOperation(Op As String) firstNumber = Val(txtDisplay.Text) activeOperation = Op isNewNumber = True End Sub Private Sub cmdClear_Click() txtDisplay.Text = "0" firstNumber = 0 secondNumber = 0 activeOperation = "" isNewNumber = True End Sub Private Sub cmdEqual_Click() secondNumber = Val(txtDisplay.Text) Select Case activeOperation Case "+" txtDisplay.Text = CStr(firstNumber + secondNumber) Case "-" txtDisplay.Text = CStr(firstNumber - secondNumber) Case "*" txtDisplay.Text = CStr(firstNumber * secondNumber) Case "/" If secondNumber <> 0 Then txtDisplay.Text = CStr(firstNumber / secondNumber) Else MsgBox "Error: Division by zero", vbCritical, "Math Error" txtDisplay.Text = "0" End If Case Else Exit Sub End Select isNewNumber = True End Sub Use code with caution. visual basic 6.0 projects with source code