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rp - RP-11/RP03 moving-head disk
The files rp0 ... rp7 refer to sections of RP disk drive 0. The files rp8 ... rp15 refer
to drive 1 etc. This allows a large disk to be broken up into more manageable pieces.
The origin and size of the pseudo-disks on each drive are as follows:
disk start length
0 0 81000
1 0 5000
2 5000 2000
3 7000 74000
Thus rp0 covers the whole drive, while rp1, rp2, rp3 can serve usefully as a root, swap,
and mounted user file system respectively.
The rp 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' interface
which provides for direct transmission between the disk and the user's read or write buf-
fer. 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
RP files begin with rrp and end with a number which selects the same disk section as the
corresponding rp file.
In raw I/O the buffer must begin on a word boundary.
In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, and write
scribbles on the tail of incomplete blocks. Thus, in programs that are likely to access
raw devices, read, write and lseek(2) should always deal in 512-byte multiples.
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