' FB 1.05.0 Win64

Function isPrime(n As Integer) As Boolean
  If n < 2 Then Return False
  If n = 2 Then Return True
  If n Mod 2  = 0 Then Return False
  Dim limit As Integer = Sqr(n)
  For i As Integer = 3 To limit Step 2
    If n Mod i = 0 Then Return False
  Next
  Return True
End Function

' To test this works, print all primes under 100
For i As Integer = 1 To 99
  If isPrime(i) Then
    Print Str(i); " ";
  End If
Next

Print : Print
Print "Press any key to quit"
Sleep