subroutine hec_beam_read(read_ok)
c
c read MWPC alignment constants from file
c Created 27-jun-1997  A.Minaenko
c
      implicit none
      logical read_ok
c
      include'hec_par.inc'      !shared parameters
      include'hec_beam_sys_shifts.inc' !MWPC alignment constants
      include'hec_datacard.inc' !datacard values
      include'hec_runh.inc'     !run header
c
      integer run_no_beam		! run number from align.const file
c
c open input file and read the constants
c
      read_ok=.false.
      open (unit=io_beam(1), file='align.const', status='old', err=2)
      read (io_beam(1), *, err=1, end=1) run_no_beam,
     ,     SHIFTX,SHIFTY,BEAMX,BEAMY
c
c check run number validity
c
      if (run_no_beam.ne.run_no) then
       print *,' *** current run_no ',run_no,
     , ', but run_no_beam in align.const file is ',run_no_beam
       stop
      endif
c
c print, close file and return
c
      print *, ' '
      print *, ' *** MWPC alignment constants have been read '
      write (*,1001) SHIFTX
 1001 format(' *   SHIFTX: ',5(f8.3,2X))
      write (*,1002) SHIFTY
 1002 format(' *   SHIFTY: ',5(f8.3,2X))
      write (*,1003) BEAMX, BEAMY
 1003 format(' *   BEAMX, BEAMY: ', 2(f8.3,2x))
      print *, ' '
      close (unit=io_beam(1))
      read_ok=.true.
      return 
c
 1    continue
      print *, ' *** error reading align.const file '
      stop
c
 2    continue
      print *, ' *** new MWPC alignment constants will be calculated'
      return
c
      end