SUBROUTINE   INIT_LOOKUP_ROUTINES ( IO_UNIT, FILE_NAME, STATUS )
C----------------------------------------------------------------------
C-
C-   Purpose and Methods : Initialize the common block for subsequent direct
C-                         access or use of library routines.
C-
C-                         This subroutine opens the Lookup Management File,
C-                         initializes the common block from the file, and
C-                         then closes the file.
C-
C-   Inputs  :
C-      IO_UNIT            Is the logical unit number to use for input file.
C-
C-      FILE_NAME          Is the name of the Lookup System Management file 
C-                         to use as input in filling the common block.
C-
C-   Outputs :
C-      STATUS             Is the initialization status.
C-                         The normally returned success status is 1.
C-                         In case of file open or read failure, the FORTRAN
C-                         IO error code is returned (positive number).
C-                         Negative numbers are reserved for file syntax
C-                         interpretation error codes.
C-
C-   filled common block : LEVEL1_LOOKUP.
C-
C-   Controls: None
C-
C-   Comments :
C-                         A call to INIT_LOOKUP_ROUTINES must be made
C-                         before any routine can be called, or any varible
C-                         accessed.
C-
C-                         The file name is passed as argument to allow
C-                         selection of a CURRENT hardware description file or
C-                         any other EXPLORATORY configuration, or retrieval
C-                         from ARCHIVES.
C-
C-                         The routine will fill with zeros all variables
C-                         referencing trigger towers whose description does
C-                         not appear in the lookup tables. The existence test
C-                         is made on the downloaded DAC byte that by
C-                         definition is non-zero only for existing Trigger
C-                         Towers.
C-
C-   Defined 21-FEB-1990 MICHIGAN STATE UNIVERSTITY, TRIGGER CONTROL SOFTWARE
C-   Created   6-JUN-1990   MICHIGAN STATE UNIVERSITY, TRIGGER CONTROL SOFTWARE
C-   Updated  10-AUG-1990   MICHIGAN STATE UNIVERSITY, TRIGGER CONTROL SOFTWARE
C-
C----------------------------------------------------------------------
      IMPLICIT NONE
C----------------------------------------------------------------------
C
C       global declarations
C
      INCLUDE  'D0$LEVEL1:PARSE_TOKENS.PARAMS'
      INCLUDE  'D0$LEVEL1:PARSE_TOKENS.INC'
C
C
C       Argument declarations
C
      INTEGER IO_UNIT
      CHARACTER*(*) FILE_NAME
      INTEGER STATUS
C
C       Local variables
C
      LOGICAL OK, ERROR
C
C
      LSM_ERROR_SEVERITY = ERROR_NONE
      LSM_ERROR_LINE = 0
      LSM_ERROR_CODE = 0
      LSM_IOSTAT = 0
C
C       open the Lookup System Management File
      CALL D0OPEN( IO_UNIT, FILE_NAME, 'IF', OK)
C
      IF (VERBOSE) THEN
        IF ( OK .EQV. .TRUE. ) THEN
          WRITE (6,*) 'Lookup description file opened.'
        ELSE
          WRITE (6,*) 'Error opening description file.'
        ENDIF
      ENDIF
      IF ( OK .EQV. .TRUE. ) THEN
C
        CALL INIT_COMMON_BLOCK_MINIMAL()
        CALL INIT_NEXT_WORD()
        CALL INIT_WIDTHS()
        CALL INIT_STRINGS()
        CALL INIT_CLASSES()
        CALL DISPATCH_MINIMAL( IO_UNIT, ERROR )
        CALL CLOSE_MGMT_FILE( IO_UNIT )
        IF (.NOT. ERROR) CALL DERIVED_QUANTITIES()
      ELSE
        LSM_ERROR_SEVERITY = ERROR_READING
        LSM_ERROR_CODE = 19
        LSM_ERROR_LINE = 0
      ENDIF
C
      IF (LSM_IOSTAT .NE. 0) THEN
        STATUS = LSM_IOSTAT
      ELSE IF (LSM_ERROR_SEVERITY .GT. ERROR_NONE) THEN
        STATUS = -LSM_ERROR_CODE
      ELSE
        STATUS = 1
      ENDIF
C
  999 CONTINUE
      END