Imports System.Math
Imports System.IO
Module Module1
 Sub Main()
  Dim x As Double = 1
  Dim xmax As Double = 100
  Dim y As Double = 0
  Dim f As Double
  Dim yn As Double
  Dim kn1, kn2, kn3, kn4 As Double
  Dim h As Double = 0.01
  Dim q As Double = 10
  Dim g As Double = 0
  Dim file As StreamWriter
  file = My.Computer.FileSystem.OpenTextFileWriter _
      ("C:\Users\Kevin C. Johnson\rungekutta.txt", False)
Start:
  If g < h Then file.Write(x.ToString("0"))
  If g < h Then file.Write(" ")
  If g < h Then file.Write(y.ToString("0.00000000000"))
  If g < h Then file.Write(" ")
  If g < h Then file.WriteLine(Log(x).ToString("0.00000000000"))
  g = g + h
  If g > q - h / 2 Then g = 0
  difeq(f, x)
  yn = y
  kn1 = f
  x = x + h / 2
  y = yn + kn1 * h / 2
  difeq(f, x)
  kn2 = f
  y = yn + kn2 * h / 2
  difeq(f, x)
  kn3 = f
  x = x + h / 2
  y = yn + kn3 * h
  difeq(f, x)
  kn4 = f
  y = yn + h * (kn1 + 2 * kn2 + 2 * kn3 + kn4) / 6
  If x < xmax + h Then GoTo Start
  file.Close()
 End Sub
 Sub difeq(ByRef f As Double, ByRef x As Double)
  f = 1 / x
 End Sub
End Module