Public Class Form1
    Dim myA, myB, myC, myD, myE, myF As Integer

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        If TextBox1.Text < 101 Then
            If TextBox1.Text <= 100 And TextBox1.Text >= 90 Then
                myA += 1
                Label1.Text = "A 등급입니다"
                Label2.Text = "A 등급 누적" & myA
            End If
            If TextBox1.Text <= 89 And TextBox1.Text >= 80 Then
                myB += 1
                Label1.Text = "B 등급입니다"
                Label3.Text = "B 등급 누적" & myB
            End If
            If TextBox1.Text <= 79 And TextBox1.Text >= 70 Then
                myC += 1
                Label1.Text = "C등급입니다"
                Label4.Text = "C 등급 누적" & myC
            End If
            If TextBox1.Text <= 69 And TextBox1.Text >= 60 Then
                myD += 1
                Label1.Text = "D 등급입니다"
                Label5.Text = "D 등급 누적" & myD
            End If
            If TextBox1.Text <= 59 And TextBox1.Text >= 50 Then
                myE += 1
                Label1.Text = "E 등급입니다"
                Label6.Text = "E 등급 누적" & myE
            End If
            If TextBox1.Text <= 49 Then
                myF += 1
                Label1.Text = "F 등급입니다"
                Label7.Text = "F 등급 누적" & myF
            End If
        Else
            Label1.Text = " 100점 보다 작아야 합니다"
        End If

        TextBox1.Text = ""
    End Sub

    Private Sub TextBox1_KeyPress(sender As System.Object, e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Not (Char.IsDigit(e.KeyChar) OrElse e.KeyChar = Convert.ToChar(Keys.Back)) Then
            e.Handled = True
        End If
    End Sub
End Class

Public Class Form1
    Dim a, b, c, d, e1, f As Integer

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If IsNumeric(TextBox1.Text) = False Then
            MsgBox("숫자를 입력하세요")
            TextBox1.Text = ""
            Return
        End If

        If CInt(TextBox1.Text) > 101 Or CInt(TextBox1.Text) < -1 Then
            MsgBox("올바른 값을 입력하세요")
            TextBox1.Text = ""
            Return
        End If

        If CInt(TextBox1.Text) > 89 Then
            Label2.Text = "A 등급" : a += 1 : Label3.Text = "A 등급 : " & a

        ElseIf CInt(TextBox1.Text) > 79 Then
            Label2.Text = "B 등급" : b += 1 : Label4.Text = "B 등급 : " & b

        ElseIf CInt(TextBox1.Text) > 69 Then
            Label2.Text = "C 등급" : c += 1 : Label5.Text = "C 등급 : " & c

        ElseIf CInt(TextBox1.Text) > 59 Then
            Label2.Text = "D 등급" : d += 1 : Label6.Text = "D 등급 : " & d

        ElseIf CInt(TextBox1.Text) > 49 Then
            Label2.Text = "E 등급" : e1 += 1 : Label7.Text = "E 등급 : " & e1

        ElseIf CInt(TextBox1.Text) < 49 Then
            Label2.Text = "F 등급" : f += 1 : Label8.Text = "F 등급 : " & f
        End If
    End Sub

    Private Sub TextBox1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.Click
        TextBox1.Text = "" : Label2.Text = ""
    End Sub
End Class