SUBROUTINE XDC210(K, Z, J)
C***BEGIN PROLOGUE  XDC210
C***DATE WRITTEN   820712   (YYMMDD)
C***REVISION DATE  831027   (YYMMDD)
C***CATEGORY NO.  A3d
C***KEYWORDS  EXTENDED-RANGE DOUBLE-PRECISION ARITHMETIC
C***AUTHOR  LOZIER, DANIEL W. (NATIONAL BUREAU OF STANDARDS)
C           SMITH, JOHN M. (NBS AND GEORGE MASON UNIVERSITY)
C***PURPOSE  TO PROVIDE DOUBLE-PRECISION FLOATING-POINT ARITHMETIC
C            WITH AN EXTENDED EXPONENT RANGE
C***DESCRIPTION
C     INTEGER K, J
C     DOUBLE PRECISION Z
C
C                  GIVEN K THIS SUBROUTINE COMPUTES J AND Z
C                  SUCH THAT  RADIX**K = Z*10**J, WHERE Z IS IN
C                  THE RANGE 1/10 .LE. Z .LT. 1.
C                  THE VALUE OF Z WILL BE ACCURATE TO FULL
C                  DOUBLE-PRECISION PROVIDED THE NUMBER
C                  OF DECIMAL PLACES IN THE LARGEST
C                  INTEGER PLUS THE NUMBER OF DECIMAL
C                  PLACES CARRIED IN DOUBLE-PRECISION DOES NOT
C                  EXCEED 60. XDC210 IS CALLED BY SUBROUTINE
C                  XDCON WHEN NECESSARY. THE USER SHOULD
C                  NEVER NEED TO CALL XDC210 DIRECTLY.
C
C***REFERENCES  (PROGRAM LISTING FOR XDSET)
C***ROUTINES CALLED  XERROR
C***COMMON BLOCKS    XDBLK3
C***END PROLOGUE  XDC210