HS(IV)                        2/9/75                       HS(IV)

     hs - RH11/RS03-RS04 fixed-head disk file

     The  files  hs0 ... hs7 refer to RJS03 disk drives 0 through
     7.  The files hs8 ... hs15 refer  to  RJS04  disk  drives  0
     through  7.   The RJS03 drives are each 1024 blocks long and
     the RJS04 drives are 2048 blocks long.

     The hs files access the disk via the system's normal buffer-
     ing  mechanism and may be read and written without regard to
     physical disk records.  There is  also  a  ``raw''  inteface
     which  provides for direct transmission between the disk and
     the user's read or write buffer.  A  single  read  or  write
     call  results in exactly one I/O operation and therefore raw
     I/O is considerably  more  efficient  when  many  words  are
     transmitted.   The names of the raw HS files begin with rhs.
     The same minor device considerations hold for the raw inter-
     face as for the normal interface.

     In  raw  I/O  the  buffer must begin on a word boundary, and
     counts should be a multiple of 512  bytes  (a  disk  block).
     Likewise  seek calls should specify a multiple of 512 bytes.

     /dev/hs?, /dev/rhs?


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