ht \- RH-11/TE-16 magtape interface
refer to the DEC RH/TM/TE-16 magtape.
When a file open for writing is closed, a double end-of-file is written.
A standard tape consists of a
series of 512 byte records terminated by an
To the extent possible, the system makes
it possible, if inefficient, to treat
the tape like any other file.
Seeks have their usual meaning and it is possible
to read or write a byte at a time.
Writing in very small units is inadvisable,
however, because it tends to create monstrous record
files discussed above are useful
when it is desired to access the tape in a way
compatible with ordinary files.
When foreign tapes are to be dealt with, and especially
when long records are to be read or written, the
`raw' interface is appropriate.
The associated files are named
call reads or writes the next record on the tape.
In the write case the record has the same length as the
During a read, the record size is passed
back as the number of bytes read, provided it is no greater
if the record is long, an error is indicated.
In raw tape I/O, the buffer must begin on a word boundary
and the count must be even.
A zero count is returned when a tape mark is read;
another read will fetch the first record of the
system call can be used to access device special functions.
This call takes the form:
.I "ioctrl(fdes, code, count)."
SKIPF: Skip blocks, forward direction
SKIPR: Skip blocks, reverse direction
SKIPFF: Skip one or more EOF's (skip forward file)
SKIPRF: Skip EOF marks or to BOT, reverse direction
argument must be positive, and specifies the number of times
the selected operation is to be repeated.
The magtape system is supposed to be able
Such addressing has never been tried.
These bugs will be fixed when
we get more experience with this device.
The driver is limited to four transports.
If any non-data error is encountered, it refuses to do anything