rk \- RK-11/RK03 or RK05 disk
refers to an entire disk as a single sequentially-addressed
Its 256-word blocks are numbered 0 to 4871.
Minor device numbers are drive numbers on one controller.
discussed above access the disk via the system's normal
and may be read and written without regard to
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 names of the raw RK files
and end with a number which selects the same disk
In raw I/O the buffer must begin on a word boundary,
and counts should be a multiple of 512 bytes
calls should specify a multiple of 512 bytes.
truncate file offsets to 512-byte block boundaries,
scribbles on the tail of incomplete blocks.
in programs that are likely to access raw devices,
should always deal in 512-byte multiples.