 
      SUBROUTINE XERROR(MESSG,NMESSG,NERR,LEVEL)
C***BEGIN PROLOGUE  XERROR
C***DATE WRITTEN   790801   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  R3C
C***KEYWORDS  ERROR,XERROR PACKAGE
C***AUTHOR  JONES, R. E., (SNLA)
C***PURPOSE  Processes an error (diagnostic) message
C***DESCRIPTION
C
C     Abstract
C        XERROR processes a diagnostic message, in a manner
C        determined by the value of LEVEL and the current value
C        of the library error control flag, KONTRL.
C        (See subroutine XSETF for details.)
C
C     Description of Parameters
C      --Input--
C        MESSG - the Hollerith message to be processed, containing
C                no more than 72 characters.
C        NMESSG- the actual number of characters in MESSG.
C        NERR  - the error number associated with this message.
C                NERR must not be zero.
C        LEVEL - error category.
C                =2 means this is an unconditionally fatal error.
C                =1 means this is a recoverable error.  (I.e., it is
C                   non-fatal if XSETF has been appropriately called.)
C                =0 means this is a warning message only.
C                =-1 means this is a warning message which is to be
C                   printed at most once, regardless of how many
C                   times this call is executed.
C
C     Examples
C        CALL XERROR(23HSMOOTH -- NUM WAS ZERO.,23,1,2)
C        CALL XERROR(43HINTEG  -- LESS THAN FULL ACCURACY ACHIEVED.,
C                    43,2,1)
C        CALL XERROR(65HROOTER -- ACTUAL ZERO OF F FOUND BEFORE INTERVAL
C    1 FULLY COLLAPSED.,65,3,0)
C        CALL XERROR(39HEXP    -- UNDERFLOWS BEING SET TO ZERO.,39,1,-1)
C
C     Written by Ron Jones, with SLATEC Common Math Library Subcommittee
C     Latest revision ---  7 Feb 1979
C***REFERENCES  JONES R.E., *SLATEC COMMON MATHEMATICAL LIBRARY ERROR
C                 HANDLING PACKAGE*, SAND78-1189, SANDIA LABORATORIES,
C                 1978.
C***ROUTINES CALLED  XERRWV
C***END PROLOGUE  XERROR
 
 
