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

     buffering  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 interface 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?