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0                                                          Ref. C3
-                    THE DEFI PACKAGE  (Ref. C3)
+                    ___ ____ _______   ___  __
0                                               Version 2
+                                               _______ _
0                                               8 March 1982
+                                               _ _____ ____
0                                               P M Girard
+                                               _ _ ______
0       This small  package provides  access under  VM  to a  CMS-
        compatible minidisk on a 3350 using 4096-byte blocks.  The
        virtual device address is 201.
0       The module,   written in Assembler,  contains  three entry
        points as follows:
0            CALL DEFI (DUMMYARG)
0       The  argument  is  not  used,  and  is  present  only  for
        historical reasons.    The routine sets  up an  RPS sector
        table for  the minidisk,  and  must be called  (once only)
        before reading or writing can begin.
0            CALL DRIN (DUMMYARG,BLOCNO,DATA)
0            CALL DROUT (DUMMYARG,BLOCNO,DATA)
0       These  routines  respectively  read  and  write  4096-byte
        blocks.   The  first argument  is not  used.   The  second
        argument is the block number relative  to the start of the
        minidisk,  counting  from 1.   The  third argument  is the
        address in store of the start of the data area.
0       Execution of the channel program is performed via DIAGNOSE
        X'18', which operates synchronously.  The return code from
        the DIAGNOSE is stored at an  address obtained by means of
        a V-type  address constant  V(C$DRIO).   This  could be  a
        FORTRAN common block named C$DRIO for instance.
0       It would  of course  be easy to  produce variants  of this
        module using a different virtual device address, different
        type of disc, or different constant block size.
0       It would   also no  doubt be  easy to  replace it  by code
        using FSOPEN, etc,  but having originally done it this way
        there is no pressing need to change it.
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0  THE DEFI PACKAGE                                         PAGE 1