 
      FUNCTION BESI0(X)
C***BEGIN PROLOGUE  BESI0
C***DATE WRITTEN   770401   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C10B1
C***KEYWORDS  BESSEL FUNCTION,FIRST KIND,HYPERBOLIC BESSEL FUNCTION,
C             MODIFIED BESSEL FUNCTION,ORDER ZERO
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the hyperbolic Bessel function of the first kind
C            of order zero
C***DESCRIPTION
C
C BESI0(X) computes the modified (hyperbolic) Bessel function
C of the first kind of order zero and real argument X.
C
C Series for BI0        on the interval  0.          to  9.00000D+00
C                                        with weighted error   2.46E-18
C                                         log weighted error  17.61
C                               significant figures required  17.90
C                                    decimal places required  18.15
C***REFERENCES  (NONE)
C***ROUTINES CALLED  BESI0E,CSEVL,INITS,R1MACH,XERROR
C***END PROLOGUE  BESI0
 
 
