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