Offset Size Contents
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  +0       4  pfData       address of the instance data (or 0000:0000 if
                           last record in the list)
  +4       2  wSize        size of the instance data, in bytes
           6               size of an SwInstanceItemRec structure

      pfData  this is the address of a data area which needs to be saved on
              each task switch and restored when that task is reactivated.
              SwInstanceItemRec structures are organized as a sequential
              list.  When pfData is 0000:0000 it indicates the end of the

       wSize  the size of the data area, in bytes. Note that the maximum
              size is 64K; but you can create two or more of these
              structures to identify a region that is larger.

 This structure is pointed to by the pfarInst field of an SwStartupInfoRec
 used in INT 2fH 4b05H (identify instance data).    It is part of the
 system that allows programs to be reentrant across multiple tasks by
 reserving memory areas for buffers and variables.

See Also: Switcher Services and Notifications
          INT 2fH 4bxxH (switcher functions)