du.4

unix v7是最后一个广泛发布的研究型UNIX版本

.TH DU 4 
.SH NAME
du, dp \- DU-11 201 data-phone interface
.SH DESCRIPTION
The
.I dp0
file
is a 201 data-phone interface.
.I Read
and
.I write
calls
to dp0
are limited to a maximum of 512 bytes.
Each write call is sent as a single record.
Seven bits from each byte
are written along with an eighth odd parity
bit.
The sync must be user supplied.
Each read call returns characters received from a
single record.
Seven bits are returned unaltered; the eighth bit
is set if the byte was not received in odd parity.
A 10 second time out is set and a zero-byte
record is returned if nothing is received in that time.
.SH FILES
/dev/dp0
.SH "SEE ALSO"
dn(4)
.SH BUGS
The name
.I dp0
is a historical dreg.