Public Function sonuc(notum As Single) As String
    Select Case notum
        Case 90 To 100
            sonuc = "A"
        Case Is >= 80
            sonuc = "B"
        Case 70 To 80
            sonuc = "C"
        Case Is >= 60
            sonuc = "D"
        Case Is >= 60
            sonuc = "D"
        Case Is >= 1
            sonuc = "F"
        Case Else
            sonuc = ""
        End Select
End Function

Function ortalama(ilk As Integer, son As Integer)
ortalama = (ilk + son) / 2
End Function