calculate prime numbers

Category:

Dates and Math

Type:

Applications

Difficulty:

Beginning

Author:

Anonymous

Version Compatibility: Visual Basic 6, Visual Basic 5

More information:

calculates all primes between to numbers entered by user, or works out if one number is prime. NOTE: program may need to be restarted each time u need to use it

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
Dim UMAX As Integer Dim UMIN As Integer Dim COUNTER As Integer Dim PRIME(1000000) As Integer Dim i As Integer Dim PMAX As Integer Dim PCOUNTER As Integer Dim number As Integer Dim FACTOR As Integer

Code:

Private Sub Command1_Click()
List1.Clear
PRIME(2) = 0
PRIME(3) = 0

UMAX = Val(txtumax.Text)
i = 3
If Val(txtumin.Text) > 0 Then
UMIN = Val(txtumin.Text)
Do
If UMIN > UMAX Then
UMIN = InputBox("Min must be smaller than Max")
End If
Loop Until UMIN <= UMAX
End If

If UMIN > 0 And UMAX > 1 Then
PRIME(1) = 2
PRIME(2) = 3
List1.AddItem PRIME(1)
List1.AddItem PRIME(2)
ElseIf UMIN > 0 And UMAX = 2 Then
PRIME(1) = 2
List1.AddItem PRIME(1)
End If

If txtumin.Text = 0 Then UMIN = UMAX
If txtumin.Text = 1 Then UMIN = 4
For COUNTER = UMIN To UMAX
    
    check

Next COUNTER

If PRIME(1) = 0 And PRIME(3) = 0 Then List1.AddItem "No primes in range"

End Sub

Public Sub check()

PMAX = 1 + (COUNTER ^ 0.5)

For PCOUNTER = 2 To PMAX

number = COUNTER / PCOUNTER
If number * PCOUNTER = COUNTER Then
PCOUNTER = PMAX
FACTOR = COUNTER
Else
PRIME(i) = COUNTER
End If
Next PCOUNTER

If PRIME(i) = COUNTER And COUNTER = FACTOR Then PRIME(i) = 0

If PRIME(i) > 0 Then List1.AddItem PRIME(i)
If PRIME(i) = COUNTER Then i = i + 1
End Sub

Private Sub Form_Load()
MsgBox ("NOTE: If minimum value is set to zero, only Maximum value will be calculated")

End Sub