Private Sub Command1_Click()
    'PROGRAM D6R1
    'Driver for routine RAN0
    'Calculates pi statistically using volume of unit n-sphere
    PI = 3.1415926
    Dim IY(3), YPROB(3)
    IDUM& = -1
    For I = 1 To 3
        IY(I) = 0
    Next I
    Print Tab(13); "Volume of unit n-sphere, n=2,3,4"
    Print Tab(5); "# points     PI         (4/3)*PI     (1/2)*PI^2"
    Randomize
    For J = 1 To 15
        For K = 2 ^ (J - 1) To 2 ^ J
            x1 = RAN0(IDUM&)
            x2 = RAN0(IDUM&)
            x3 = RAN0(IDUM&)
            x4 = RAN0(IDUM&)
            If (FNC(x1, x2, 0#, 0#) < 1#) Then IY(1) = IY(1) + 1
            If (FNC(x1, x2, x3, 0#) < 1#) Then IY(2) = IY(2) + 1
            If (FNC(x1, x2, x3, x4) < 1#) Then IY(3) = IY(3) + 1
        Next K
        For I = 1 To 3
            YPROB(I) = 1# * (2 ^ (I + 1)) * IY(I) / (2 ^ J)
        Next I
        Print Tab(5); 2 ^ J;
        For M = 1 To 3
            Print Tab(15 + (M - 1) * 14); Format$(YPROB(M), "#.#####0");
        Next M
    Next J
    Print Tab(5); "actual"; Tab(15); Format$(PI, "#.#####0");
    Print Tab(29); Format$(4# * PI / 3#, "#.#####0");
    Print Tab(43); Format$(0.5 * (PI ^ 2), "#.#####0")
End Sub
Function FNC(x1, x2, x3, x4)
    FNC = Sqr(x1 ^ 2 + x2 ^ 2 + x3 ^ 2 + x4 ^ 2)
End Function