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

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

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