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Annotation of 41BSD/sys/newsys/tm.4, revision 1.1

1.1     ! root        1: .TH HT 4 
        !             2: .SH NAME
        !             3: ht \- RH-11/TE-16 magtape interface
        !             4: .SH DESCRIPTION
        !             5: The files
        !             6: .I "mt0, ..., mt15"
        !             7: refer to the DEC RH/TM/TE-16 magtape.
        !             8: Even numbered files are 800 bpi, and odd numbered
        !             9: files are 1600bpi.
        !            10: The files
        !            11: .I "mt0, ..., mt15"
        !            12: are rewound when closed; the files
        !            13: .I "nmt0, ... nmt15"
        !            14: are not.
        !            15: When a file open for writing is closed, a double end-of-file is written.
        !            16: .PP
        !            17: A standard tape consists of a
        !            18: series of 512 byte records terminated by an
        !            19: end-of-file.
        !            20: To the extent possible, the system makes
        !            21: it possible, if inefficient, to treat
        !            22: the tape like any other file.
        !            23: Seeks have their usual meaning and it is possible
        !            24: to read or write a byte at a time.
        !            25: Writing in very small units is inadvisable,
        !            26: however, because it tends to create monstrous record
        !            27: gaps.
        !            28: .PP
        !            29: The
        !            30: .I mt
        !            31: files discussed above are useful
        !            32: when it is desired to access the tape in a way
        !            33: compatible with ordinary files.
        !            34: When foreign tapes are to be dealt with, and especially
        !            35: when long records are to be read or written, the
        !            36: `raw' interface is appropriate.
        !            37: The associated files are named
        !            38: .I "rmt0, ..., rmt15,"
        !            39: and
        !            40: .I "nrmt0, ..., nrmt15."
        !            41: .PP
        !            42: Each
        !            43: .I read
        !            44: or
        !            45: .I write
        !            46: call reads or writes the next record on the tape.
        !            47: In the write case the record has the same length as the
        !            48: buffer given.
        !            49: During a read, the record size is passed
        !            50: back as the number of bytes read, provided it is no greater
        !            51: than the buffer size;
        !            52: if the record is long, an error is indicated.
        !            53: In raw tape I/O, the buffer must begin on a word boundary
        !            54: and the count must be even.
        !            55: Seeks are ignored.
        !            56: A zero count is returned when a tape mark is read;
        !            57: another read will fetch the first record of the
        !            58: next tape file.
        !            59: .PP
        !            60: In raw mode, the 
        !            61: .I ioctl
        !            62: system call can be used to access device special functions.
        !            63: This call takes the form:
        !            64: .I "ioctrl(fdes, code, count)."
        !            65: Codes are defined in 
        !            66: .I "<sys/mt.h>,"
        !            67: and consist of:
        !            68: .in +8
        !            69: .ti -3
        !            70: SKIPF: Skip blocks, forward direction
        !            71: .ti -3
        !            72: SKIPR: Skip blocks, reverse direction
        !            73: .ti -3
        !            74: WEOF: Write EOF
        !            75: .ti -3
        !            76: REW: Rewind
        !            77: .ti -3
        !            78: SKIPFF: Skip one or more EOF's (skip forward file)
        !            79: .ti -3
        !            80: SKIPRF: Skip EOF marks or to BOT, reverse direction
        !            81: .in -8
        !            82: The
        !            83: .I count
        !            84: argument must be positive, and specifies the number of times
        !            85: the selected operation is to be repeated.
        !            86: .SH FILES
        !            87: /dev/mt?,
        !            88: /dev/rmt?
        !            89: .SH "SEE ALSO"
        !            90: tp(1)
        !            91: .SH BUGS
        !            92: The magtape system is supposed to be able
        !            93: to take 64 drives.
        !            94: Such addressing has never been tried.
        !            95: These bugs will be fixed when
        !            96: we get more experience with this device.
        !            97: .PP
        !            98: The driver is limited to four transports.
        !            99: .PP
        !           100: If any non-data error is encountered, it refuses to do anything
        !           101: more until closed.

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