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Annotation of researchv10dc/man/manb/ht.4, revision 1.1.1.1

1.1       root        1: .TH HT 4 
                      2: .UC 4
                      3: .SH NAME
                      4: ht \- RH-11/TE-16 magtape interface
                      5: .SH DESCRIPTION
                      6: The files
                      7: .I "mt0, ..., mt15"
                      8: refer to the DEC RH/TM/TE-16 magtape.
                      9: The files
                     10: .I "mt0, ..., mt7"
                     11: are 800 bpi, and
                     12: .I "mt8, ..., mt15"
                     13: are 1600bpi.
                     14: The files
                     15: .I "mt0, ..., mt3"
                     16: and
                     17: .I "mt8, ..., mt11"
                     18: are rewound when closed; the others are not.
                     19: When a file open for writing is closed, a double end-of-file is written.
                     20: .PP
                     21: A standard tape consists of a
                     22: series of 1024 byte records terminated by an
                     23: end-of-file.
                     24: To the extent possible, the system makes
                     25: it possible, if inefficient, to treat
                     26: the tape like any other file.
                     27: Seeks have their usual meaning and it is possible
                     28: to read or write a byte at a time.
                     29: Writing in very small units is inadvisable,
                     30: however, because it tends to create monstrous record
                     31: gaps.
                     32: .PP
                     33: The
                     34: .I mt
                     35: files discussed above are useful
                     36: when it is desired to access the tape in a way
                     37: compatible with ordinary files.
                     38: When foreign tapes are to be dealt with, and especially
                     39: when long records are to be read or written, the
                     40: `raw' interface is appropriate.
                     41: The associated files may be named
                     42: .I "rmt0, ..., rmt15,"
                     43: but the same minor-device considerations
                     44: as for the regular files still apply.
                     45: .PP
                     46: Each
                     47: .I read
                     48: or
                     49: .I write
                     50: call reads or writes the next record on the tape.
                     51: In the write case the record has the same length as the
                     52: buffer given.
                     53: During a read, the record size is passed
                     54: back as the number of bytes read, provided it is no greater
                     55: than the buffer size;
                     56: if the record is long, an error is indicated.
                     57: In raw tape I/O, the buffer must begin on a word boundary
                     58: and the count must be even.
                     59: Seeks are ignored.
                     60: A zero count is returned when a tape mark is read;
                     61: another read will fetch the first record of the
                     62: next tape file.
                     63: .SH FILES
                     64: /dev/mt\(**,
                     65: /dev/rmt\(**
                     66: .SH "SEE ALSO"
                     67: tp(1)
                     68: .SH BUGS
                     69: The magtape system is supposed to be able
                     70: to take 64 drives.
                     71: Such addressing has never been tried.
                     72: These bugs will be fixed when
                     73: we get more experience with this device.
                     74: .PP
                     75: The driver is limited to four transports.
                     76: .PP
                     77: If any non-data error is encountered, it refuses to do anything
                     78: more until closed.
                     79: In raw I/O, there should be a way
                     80: to perform forward and backward record and file spacing and
                     81: to write an EOF mark explicitly.

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