Type CheckStand
    Done As Long
    text As String *  20 
    Client As String *  8 
End Type

Private Sub chkOpen_Click()
    Dim usename$
    Dim InitialStand As CheckStand
    Dim written&
    usename$ = "ChkStd" & txtCheck.text
    If chkOpen.value =  1  Then
        If FileHandle <>  0  Then Exit Sub
        FileHandle = CreateFile(usename$, GENERIC_READ Or GENERIC_WRITE, _
                                 0 , Security, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL Or FILE_FLAG_RANDOM_ACCESS,  0 )
        If FileHandle = - 1  Then
            MsgBox "Can't create file"
            FileHandle = 0
            Exit Sub
        End If
        Call WriteFile(FileHandle, InitialStand, Len(InitialStand), written, 0)
        Call FlushFileBuffers(FileHandle)
        MappingHandle = CreateFileMapping(FileHandle, Security, PAGE_READWRITE, 0, 0, usename$ & "map")
        If MappingHandle = 0 Then
            MsgBox "Can't create file mapping"
            Exit Sub
        End If
        MappingAddress = MapViewOfFile(MappingHandle, FILE_MAP_ALL_ACCESS,  0 ,  0 ,  0 )
        If MappingAddress =  0  Then
            MsgBox "Can't map view of the file"
            Exit Sub
        End If
        Timer1.Enabled = True
    Else
        CleanUp
        lblStatus.Caption = "Closed"
    End If
End Sub

Private Sub Form_Load()
    With Security
        .nLength = Len(Security)
        .lpSecurityDescriptor =  0 
        .bInheritHandle = True
    End With
End Sub

Private Sub Form_Unload(Cancel As Integer)
    CleanUp
End Sub

Private Sub CleanUp()
    Timer1.Enabled = False
    If MappingAddress <>  0  Then
        Call UnmapViewOfFile(MappingAddress)
        MappingAddress =  0 
    End If
    If MappingHandle <>  0  Then
        Call CloseHandle(MappingHandle)
        MappingHandle =  0 
    End If
    If FileHandle <>  0  Then
        Call CloseHandle(FileHandle)
        FileHandle =  0 
    End If
End Sub

Private Sub Timer1_Timer()
    Dim cs As CheckStand
    agCopyData ByVal MappingAddress, cs, Len(cs)
    If cs.Done =  1  Then
            lstCustomers.AddItem cs.text
            cs.Done =  0 
            Timer1.Enabled = False
            lblStatus.Caption = "Waiting to pay"
    Else
        lblStatus.Caption = "Waiting for customer"
    End If
    
End Sub

Private Sub Timer1_Timer()
    Dim usename$
    Dim newtotal&
    Dim cs As CheckStand
    Dim x%
      
    Select Case CurrentState
        Case  0 
            If chkShop.value =  1  Then
                CurrentState =  1 
            End If
        Case  1 
            usename$ = GetMappingName$()
            MappingHandle = OpenFileMapping(FILE_MAP_WRITE, False, usename$)
            If MappingHandle =  0  Then Exit Sub
            MappingAddress = MapViewOfFile(MappingHandle, FILE_MAP_ALL_ACCESS,  0 ,  0 ,  0 )
            CurrentState =  2 
        Case  2 
            CurrentState =  3 
        Case  3 
            Open "C:\config.ini" For Input As # 1 
            If Not EOF( 1 ) Then
               Line Input # 1 , cs.text
            End If
            Close # 1 
            cs.Done =  1 
            cs.Client = "Client" & txtClient.text
            agCopyData cs, ByVal MappingAddress, Len(cs)
            CurrentState =  4 
            CleanUp
    End Select
End Sub

Public Function GetMappingName() As String
    GetMappingName = "ChkStd1map"
End Function

Private Sub CleanUp()
    If MappingAddress <>  0  Then
        Call UnmapViewOfFile(MappingAddress)
        MappingAddress =  0 
    End If
    If MappingHandle <>  0  Then
        Call CloseHandle(MappingHandle)
        MappingHandle =  0 
    End If
End Sub