    RF(IV)                       10/15/73                      RF(IV)

    NAME
         rf - RF11/RS11 fixed-head disk file

    DESCRIPTION
         This file refers to the concatenation of all RS-11 disks.

         Each  disk contains 1024 256-word blocks.  The length of the
         combined RF file is 1024X(minor+1) blocks.   That  is  minor
         device  zero  is  taken to be 1024 blocks long; minor device
         one is 2048, etc.

         The rf0 file accesses  the  disk  via  the  system's  normal
         buffering  mechanism and may be read and written without re-
         gard to physical disk records.  There is also a ``raw''  in-
         terface  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 there-
         fore raw I/O is considerably more efficient when many  words
         are  transmitted.  The name of the raw RF file is rrf0.  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.

    FILES
         /dev/rf0, /dev/rrf0

    BUGS
         The 512-byte restrictions on the raw device are  not  physi-
         cally necessary, but are still imposed.

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