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RF(4)                      Kernel Interfaces Manual                      RF(4)

       rf - RF11/RS11 fixed-head disk file

       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 mecha-
       nism and may be read  and  written  without  regard  to  physical  disk
       records.   There  is  also  a `raw' interface 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  name  of  the  raw RF file is rrf0.  The same minor
       device considerations hold for the raw  interface  as  for  the  normal

       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/rf0, /dev/rrf0

       The  512-byte  restrictions on the raw device are not physically neces-
       sary, but are still imposed.