Outputting sine waves on xy plots — stuck on certain parts - vb.net

Question

Please help I want to know exactly what is going on in this code for a questions and answers exam tomorrow.
I don't need any help with writing the code because that would be cheating. I made a tiny few mistakes please forgive me I rectified most of theses I don't need help with the mistakes just with the comments and understanding mostly how it works.
Private Sub Command1_Click()
MSComm1.Output = "83" + Chr$(13)
End Sub
Private Sub Form_Load()
MSC1.PortOpen = True
Average_val = 0
minimum_val = 255
maximum_val = 0
Screenshotofsinewave.Left = 0
Screenshotofsinewave.Channel(0).TraceVisible = True
Screenshotofsinewave.Channel(0).MarkersVisible = True
sumofall_val = 0
Screenshotofsinewave.TitleVisible = False
Screenshotofsinewave.Top = 0
Screenshotofrectifiedsinewave.TitleVisible = False
Screenshotofrectifiedsinewave.Channel(0).TraceVisible = True
Screenshotofrectifiedsinewave.Channel(0).MarkersVisible = True
Screenshotofrectifiedsinewave.Top = 0
Screenshotofrectifiedsinewave.Left = 0
Screenshotoflevelshiftedsinewave.Top = 0
Screenshotoflevelshiftedsinewave.Left = 0
Screenshotoflevelshiftedsinewave.TitleVisible = False
Screenshotoflevelshiftedsinewave.Channel(0).TraceVisible = True
Screenshotoflevelshiftedsinewave.Channel(0).MarkersVisible = True
End Sub
Private Sub MSC1_OnComm()
Dim number_val
Dim number1_val
Dim Average_val
Dim com1_val
p = 0
q = 0
r = 0
s = 0
t = 0
Dim Xarr(50) As Single
Dim Yarr(50) As Single
Dim number2_val
Dim number3_val
Dim Snapshotofsinewave
Dim string1_out As String
Dim string1_in As String
Dim counter As Single
Dim sample_rate As Integer
Select Case MSC1.CommEvent
Case comEvReceive
minimum_val = 255
string1_in = MSC1.Input
Screenshotofsinewave.Channel(0).Clear
Screenshotofrectifiedsinewave.Channel(0).Clear
Screenshotoflevelshiftedsinewave.Channel(0).Clear
counter = 0
comm_count = comm_count + 1
For sample_rate = 1 To 150 Step 3
string1_out = Mid(string1_in, sample_rate, 3)
counter = counter + 1
number_val = Val(string1_out)
Xarr(counter) = counter
Yarr(counter) = number_val
Screenshotofsinewave.Channel(0).AddXY counter, number_val
If number_val > maximum_val Then
maximum_val = number_val
MaxVoltage.Value = maximum_val
End If
If number_val < minimum_val Then
minimum_val = number_val
MinVoltage.Value = number_val
End If
sumofall_val = number_val + sumofall_val
Average_value = sumofall_val / 50
AverageVoltage.Value = Average_value
Next sample_rate
counter = 0
sumofall_val = 0
For sample_rate = 1 To 150 Step 3
string1_out = Mid(string1_in, sample_rate, 3)
counter = counter + 1
number_val = Val(string1_out)
number_val = number1_val - Average_value
number_val = numer_val
If num_val1 < 0 Then
number_val = number_val * -1
End If
Xarr(counter) = counter
Yarr(counter) = number1_val
Screenshotofrectifiedsinewave.Channel(0).AddXY counter, number1_val
Next sample_rate
counter = 0
For sample_rate = 1 To 150 Step 3
string1_out = Mid(string1_in, sample_rate, 3)
Count = Count + 1
number_val = Val(string1_out)
number2_val = number_val + Average_value
Xarr(Count) = counter
Yarr(Count) = number2_val
LevelShifted.Channel(0).AddXY Count, number_val2
sumofall_val = number_val + sumofall_val
Next sample_rate
counter = com1_val
Snapshotofsinewave.Value = com1_val
End Select
End Sub
Private Sub Frame4_DragDrop(Source As Control, X As Single, Y As Single)
End Sub
Private Sub Uploaddata_Click()
If GXSwitch1.SwitchOn = True Then
led1.LampOn = True
p = 8
Else
led1.LampOn = False
p = 0
End If
If GXSwitch2.SwitchOn = True Then
led2.LampOn = True
q = 4
Else
led2.LampOn = False
q = 0
End If
If GXSwitch3.SwitchOn = True Then
led3.LampOn = True
r = 4
Else
led3.LampOn = False
r = 0
End If
If GXSwitch4.SwitchOn = True Then
led4.LampOn = True
s = 8
Else
led4.LampOn = False
s = 0
End If
t = p + q + r + s
If t = 0 Then
MSC1.Output = "0" + Chr$(13)
End If
If t = 1 Then
MSC1.Output = "1" + Chr$(13)
End If
If t = 2 Then
MSC1.Output = "2" + Chr$(13)
End If
If t = 3 Then
MSC1.Output = "3" + Chr$(13)
End If
If t = 4 Then
MSC1.Output = "4" + Chr$(13)
End If
If t = 5 Then
MSC1.Output = "5" + Chr$(13)
End If
If t = 6 Then
MSC1.Output = "6" + Chr$(13)
End If
If t = 7 Then
MSC1.Output = "7" + Chr$(13)
End If
If t = 8 Then
MSC1.Output = "8" + Chr$(13)
End If
If t = 9 Then
MSC1.Output = "9" + Chr$(13)
End If
If t = 10 Then
MSC1.Output = "10" + Chr$(13)
End If
If t = 11 Then
MSC1.Output = "11" + Chr$(13)
End If
If t = 12 Then
MSC1.Output = "12" + Chr$(13)
End If
If t = 13 Then
MSC1.Output = "13" + Chr$(13)
End If
If t = 14 Then
MSC1.Output = "14" + Chr$(13)
End If
If t = 15 Then
MSC1.Output = "15" + Chr$(13)
End If
End Sub

Answer 1

Depends on several factors...
Dim average_val, x As Decimal ' decimal
Dim average_val = 3.2D ' decimal if Option Infer On
Dim average_val = 3.2D ' object with boxed decimal if Option Infer Off
Dim average_val ' Object if Option Strict Off, otherwise an error