APPENDIX B : FORMAT OF WORK BANKS

            The structure of work bank is as follows:-

        Word (Integer)  Contents   Description

             IND-3        NAME    Bank Name (4 ASCII Characters)
             IND-2          NT    Total number of words of the bank
             IND-1         IND    Pointer to index of bank
             IND            ND    Number of data words
             IND+1                Data word 1
             IND+2                Data word 2
               ...                ...
             IND+ND               Data word ND


            N.B.

           (a)  All work banks  are  Integer  oriented.   Thus  their
                total  length is always an integral number of Integer
                words.  The internal  representation  of  the  user's
                data  within  the  data  area of the bank need not be
                Integer, being  at  the  choice  of  the  Application
                Programmer.

           (b)  As previously noted the name for a work bank  has  no
                function  other than as a debugging aid.  If required
                the  name  should  be  setup  explicitly  by  setting
                IW(IND-3) to the desired Hollerith string.

           (c)  The total number of words of the bank NT  allows  the
                possibility   of   decreasing   (and  in  some  cases
                increasing) the number of  data  words  in  the  bank
                without moving other work banks.

           (d)  The Pointer to index of bank is used  to  update  the
                index  IND  automatically during garbage collections,
                etc.

           (e)  The number of data words ND may be less than or equal
                to NT-4.
       FORMAT OF WORK BANKS                                  Page B-2



            Each work bank contains a pointer to  the  index  of  the
       bank.   This  pointer  enables  the  bank  to be automatically
       tracked if it is moved during garbage  collections.   Consider
       the following code fragment:-

       C
       C       Create a Work Bank with ND Data words
       C
       C       Arguments to WBANK are:-
       C
       C       JW      YBOS Array Name
       C       IND     Returned Index to the Bank....STATIC variable
       C       ND      No. of Datawords in Bank
       C
             STATUS = WBANK(JW,IND,ND)
             JND    = IND
       C
       C       Perform Garbage Collection on Workbanks
       C
             STATUS = WGARB(JW)
             .....

       This code fragment will create a work bank such that  variable
       IND  points  to  the  bank  - i.e. JW(IND) contains the no. of
       datawords, JW(IND+1)  is  the  first  dataword  etc.   If  the
       workbank   is   moved   through  the  action  of  the  garbage
       collection, the contents of the variable IND will be  modified
       such  that  JW(IND)  still  contains the no. of datawords etc.
       However, JND will not  be  updated  in  this  manner,  and  an
       attempt  to  access  the  contents of the workbank via JW(JND)
       etc. may cause unpredictable results.  YBOS allows work  banks
       to  be  locked  temporarily  such  that  movement  of  them is
       inhibited (see WLOCK and WUNLK).