VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   5100
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   4155
   LinkTopic       =   "Form1"
   ScaleHeight     =   5100
   ScaleWidth      =   4155
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   2400
      TabIndex        =   0
      Top             =   4440
      Width           =   1215
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
    'PROGRAM D4R15
    'Driver for routine BESSJ0
    Open "D:\VB常用數值算法集\DATA\FNCVAL.DAT" For Input As #1
    Do
      Line Input #1, Text$
    Loop While Text$ <> "Bessel Function J0"
    Line Input #1, NVAL$
    NVAL = Val(NVAL$)
    Print Text$
    Print
    Print "     X      Actual      BESSJ0(X)"
    For I = 1 To NVAL
        Line Input #1, DUM$
        X = Val(Mid(DUM$, 1, 6))
        Value = Val(Mid(DUM$, 7))
        Print Tab(4); Format$(X, "#0.0#");
        Print Tab(12); Format$(Value, "##.0000000");
        Print Tab(25); Format$(BESSJ0(X), "##.0000000")
    Next I
    Close #1
End Sub
Function BESSJ0(X)
    P1# = 1#:                  P2# = -0.001098628627
    P3# = 0.00002734510407:    P4# = -0.000002073370639
    P5# = 2.093887211E-07
    Q1# = -0.01562499995:      Q2# = 0.0001430488765
    Q3# = -0.000006911147651:  Q4# = 7.621095161E-07
    Q5# = -9.34945152E-08:
    R1# = 57568490574#:        R2# = -13362590354#
    R3# = 651619640.7:         R4# = -11214424.18
    R5# = 77392.33017:         R6# = -184.9052456
    S1# = 57568490411#:        S2# = 1029532985#
    S3# = 9494680.718:         S4# = 59272.64853
    S5# = 267.8532712:         S6# = 1#
    If Abs(X) < 8# Then
       y# = X * X
       BBB# = y# * (R4# + y# * (R5# + y# * R6#))
       AAA# = R1# + y# * (R2# + y# * (R3# + BBB#))
       CCC# = y# * (S3# + y# * (S4# + y# * (S5# + y# * S6#)))
       BESSJ0 = AAA / (S1# + y# * (S2# + CCC#))
    Else
       AX# = Abs(X)
       Z# = 8# / AX#
       y# = Z# * Z#
       XX = AX# - 0.785398164
       CCC# = y# * (P3# + y# * (P4# + y# * P5#))
       AAA# = P1# + y# * (P2# + CCC#)
       DDD# = y# * (Q3# + y# * (Q4# + y# * Q5#))
       EEE# = Z# * Sin(XX) * (Q1# + y# * (Q2# + DDD#))
       BESSJ0 = Sqr(0.636619772 / AX#) * (Cos(XX) * AAA# - EEE#)
    End If
End Function