[unix-history] / usr / man / man4 / rk.4

.TH RK 4 
.SH NAME
rk \- RK-11/RK03 or RK05 disk
.SH DESCRIPTION
.I Rk?
refers to an entire disk as a single sequentially-addressed
file.
Its 256-word blocks are numbered 0 to 4871.
Minor device numbers are drive numbers on one controller.
.PP
The
.I rk
files
discussed above 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 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
begin with
.I rrk
and end with a number which selects the same disk
as the corresponding
.I rk
file.
.PP
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
.I seek
calls should specify a multiple of 512 bytes.
.SH FILES
/dev/rk?, /dev/rrk?
.SH BUGS
In raw I/O
.I read
and
.IR write (2)
truncate file offsets to 512-byte block boundaries,
and
.I write
scribbles on the tail of incomplete blocks.
Thus,
in programs that are likely to access raw devices,
.I read, write
and
.IR lseek (2)
should always deal in 512-byte multiples.
Commit	Line	Data
16773074 BJ	1	.TH RK 4
	2	.SH NAME
	3	rk \- RK-11/RK03 or RK05 disk
	4	.SH DESCRIPTION
	5	.I Rk?
	6	refers to an entire disk as a single sequentially-addressed
	7	file.
	8	Its 256-word blocks are numbered 0 to 4871.
	9	Minor device numbers are drive numbers on one controller.
	10	.PP
	11	The
	12	.I rk
	13	files
	14	discussed above access the disk via the system's normal
	15	buffering mechanism
	16	and may be read and written without regard to
	17	physical disk records.
	18	There is also a `raw' interface
	19	which provides for direct transmission between the disk
	20	and the user's read or write buffer.
	21	A single read or write call results in exactly one I/O operation
	22	and therefore raw I/O is considerably more efficient when
	23	many words are transmitted.
	24	The names of the raw RK files
	25	begin with
	26	.I rrk
	27	and end with a number which selects the same disk
	28	as the corresponding
	29	.I rk
	30	file.
	31	.PP
	32	In raw I/O the buffer must begin on a word boundary,
	33	and counts should be a multiple of 512 bytes
	34	(a disk block).
	35	Likewise
	36	.I seek
	37	calls should specify a multiple of 512 bytes.
	38	.SH FILES
	39	/dev/rk?, /dev/rrk?
	40	.SH BUGS
	41	In raw I/O
	42	.I read
	43	and
	44	.IR write (2)
	45	truncate file offsets to 512-byte block boundaries,
	46	and
	47	.I write
	48	scribbles on the tail of incomplete blocks.
	49	Thus,
	50	in programs that are likely to access raw devices,
	51	.I read, write
	52	and
	53	.IR lseek (2)
	54	should always deal in 512-byte multiples.