
  THE /EVENT COMMON IS THE STACK, WHERE ALL PARTICLES PRODUCED
  IN A SHOWER ARE STORED. ONE TRACK HAS 12 LOCATIONS .

  NSIZE = TOTAL LENGTH OF THE STACK (TO BE SET IN BLOCK-DATA)
  NCUR  = POINTER TO THE TRACK WHICH SHOULD BE COPIED NEXT FROM
          THE STACK TO THE RESULT-COMMON.
  NEXT  = POINTER TO THE LOCATION WHERE THE NEXT PRODUCED TRACK
          SHOULD BE STORED.
  NTOT  = TOTAL NUMBER OF TRACKS CURRENTLY STORED.

  THE TRACK NEXT TO BE COPIED FROM THE STACK THEN LOOKS LIKE

  EVENT(NCUR   ) = X
  EVENT(NCUR+ 1) = Y
  EVENT(NCUR+ 2) = Z
  EVENT(NCUR+ 3) = RCA
  EVENT(NCUR+ 4) = RCE
  EVENT(NCUR+ 5) = MASS
  EVENT(NCUR+ 6) = CHARGE
  EVENT(NCUR+ 7) = TOF
  EVENT(NCUR+ 8) = PX
  EVENT(NCUR+ 9) = PY
  EVENT(NCUR+10) = PZ
  EVENT(NCUR+11) = USERW


