APPENDIX F : EXAMPLES

       F.1  MAIN PROGRAM IN STANDARD EVENT PROCESSING

            The MAIN program below reads one event  at  a  time  from
       logical  unit  10,  calls processing subprograms and add extra
       data to the event and then writes the event  to  logical  unit
       20.   All  banks  of  the  event are then dropped and, after a
       garbage collection, the process is repeated.

             COMMON/BCS/IW(10000)
       C
       C          Initalize YBOS and open logical units
       C
             STATUS = BOS77(10000,0)
             STATUS = BLOPEN(10,2048)
             STATUS = BLOPEN(20,2048)
       C
       C          Read one event from unit 10, check for EOF.
       C          Note that the 'E' Bank Set will contain all
       C          Banks from the Logical Record after the call.
       C          If 'E+' had been used instead of 'E', then the
       C          Bank Set would have contained both the Banks 
       C          in the Logical Record and any other Banks that
       C          were already contained in the 'E' Set.
       C
       100   STATUS = BLREAD(10,IW,'E',NWORDS)
             if (IW(2) .eq. 3) go to 500
       C
       C          Call processing subprograms
       C
             .....
             .....
             .....
       C
       C          add bank 'BERT' and delete banks 'CARL' and 'DAVE'
       C
             STATUS = BLIST(IW,'E+','BERT')
             STATUS = BLIST(IW,'E-','CARLDAVE')
       C
       C          Write event to unit 20 and drop banks etc.
       C
             STATUS = BLWRIT(20,IW,'E')
             STATUS = BDROP(IW,'E')
             STATUS = BGARB(IW)
             go to 100
       C
       C          end of file - close units etc.
       C
       500   STATUS = BLCLOS(10)
             STATUS = BLCLOS(20)
             stop
             end



       F.2  SIMPLE HISTOGRAM PACKAGE

            The following example shows how  a  simple  histogramming
       package may be set up.

             subprogram BHIST(NR,N,XA,XB)
       C
       C          Book histogram NR with N bins between XA and XB
       C
             COMMON/HCS/KW(1)
             real XW(1)
             equivalence (KW(1),XW(1))
       C
       C          Check already booked
       C
             if (MLINK(KW,'HIST',NR) .ne. 0) go to 100
       C
       C          Create histogram bank. The format is:-
       C
       C          1    N = Number of Bins
       C          2    XA = Lowest Channel Left Edge
       C          3    XB = Highest Channel Right Edge
       C          4    DX = Bin Width
       C          5    Content outside Low
       C          6    Content outside High
       C          7    Content first Bin
       C        ...    ...
       C        6+N    Content last Bin
       C
             IND = MBANK(KW,'HIST',NR,N+6)
             if (IND .eq. 0) go to 100
             KW(IND+1) = N
             XW(IND+2) = XA
             XW(IND+3) = XB
             XW(IND+4) = (XB-XA)/FLOAT(N)
       C
       C          Return to caller
       C
       100   return
             end


             subprogram EHIST(NR,X)
       C
       C          add entry X to histogram NR
       C
             COMMON/HCS/KW(1)
             real XW(1)
             equivalence (KW(1),XW(1))
       C
       C          Find histogram bank
       C
             IND = MLINK(KW,'HIST',NR)
             if (IND .ne. 0) then
                I = 1.0 + (X-XW(IND+2))/XW(IND+4)
                if (I .lt. 1) I = -1
                if (I .gt. KW(IND+)) I = 0
       C
       C       add 1.0 to bin content
       C
                XW(IND+6+I) = XW(IND+6+I)+1.0
             endif
             return
             end