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These were all files included in MIT's 1999 release of SYSDOC and SYSTEM, so they need the license header. CHAORD is an XGP text file; XGP processors should ignore unknown directives so ;comment should work.
210 lines
5.4 KiB
Plaintext
Executable File
210 lines
5.4 KiB
Plaintext
Executable File
Copyright (c) 1999 Massachusetts Institute of Technology
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See the COPYING file at the top-level directory of this project.
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------------------------------
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MAG TAPE SPECS
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Copied from memo from S.Cutler 2/23/72
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THIS MEMO CONTAINS MANY LOWER-CASE CHARS
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Bits in left half word of .OPEN call:
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3.1=1,,0
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0=> Input
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1=> Output
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3.2=2,,0
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0=> Unit
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1=> Block
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3.3=4,,0
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0=> ASCII
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1=> Image
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3.4=10,,0
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0=> Ignore record gaps,treat them as part of the hardware
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1=> "Chunk mode." [does not appear to be implemented any more]
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If output then write an EOR gap after each .IOT.
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If input, if user defined block IOT pointer is big enough
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one record is read. See .IOT for details. Must be
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opened in block mode.
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3.5=20,,0
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0=> Skip to EOF on last close on read
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1=> Don't " " " " " " "
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3.6=40,,0
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0=> Odd parity
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1=> Even parity
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3.7,8=300,,0
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00=> default (800 or 1600 BPI depending on drive type)
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01=> 800 BPI (used to be 200 BPI)
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10=> 1600 BPI (used to be 556 BPI)
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11=> 6250 BPI (used to be 800 BPI)
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3.9=400,,0 Only meaningful for 9 track tapes
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0=> Core dump mode, 36 bit words, any density allowed.
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1=> IBM Character Mode, 32 bit words, doesn't allow 200/556 BPI
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4.1,2,3=7000,,0
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0=> 2000=1024. words per record
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1=> 1000=512. WPR
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2=> 400=256. WPR
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3=> 200=128. WPR
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4=> 100=64. WPR
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5=> 40=32. WPR
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6=> 20=16. WPR
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7=> 10=8. WPR
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Open error if:
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1) Open for writing and
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a) Open for reading on another channel
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b) Tape write locked (i.e. no ring)
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c) IBM mode and less than 800 BPI
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2) Open for reading and already open for writing on another
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channel
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3) Transport not on line
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4) Chunk mode and not block mode
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.IOT CHNM,LOC
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-------------
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For standard .OPEN, this works as a standard .IOT. If open
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in chunk mode input [not implemented any more], loc has
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loc/ -count,,loc2
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where count is a number greater than the possible number of words to
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be written into core. The .IOT causes words to be read into core
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starting at loc2. For each word read, the count in decreased by one.
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An IOC error occurs if the count is too small to contain the
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record.
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On chunk mode output, an EOR gap is written after each .IOT,
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and the tape is written after each .IOT instead of waiting for
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system buffers to fill or the channel closed. [not implemented any more]
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.CLOSE CHNM,
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------------
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Closes the channel, releases the transport if not open on another
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channel. Writes out all buffers in the system and writes 2 EOF
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marks if open for writing, and backs up over second one.
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.STATUS CHNM,LOC
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----------------
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1.1-1.6=> physical device code (15)
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1.7-1.9 mode open in
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2.1=> System buffering capacity empty (i.e. 0=> data read from
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tape and not yet transferred to user by a .IOT or data
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.IOTed from the user to the system but not actually
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written onto tape or user core image.)
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2.2=> System buffering capacity full (i.e. no core in which to
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allocate buffers for reading from tape. Also too many
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buffers resident in system but not yet written onto either
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tape or users core image.)
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2.3=> 1=> Beginning of tape
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2.4=> 1=> End of tape
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2.5=> 1=> 9 track, 0=> 7 track
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2.6=> 1=>IBM mode, 0=> core dump mode
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2.7=> Transport idle (no pending command)
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2.8=> EOF (last thing seen was a tape mark)
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Left half standard.
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.RCHST AC,
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----------
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AC/ CHNM,,LOC
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LOC: 0) 0,,(SIXBIT /MTn/)
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1) 0
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2) 0
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3) 0
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4) -1
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.MTAPE AC,
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----------
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AC/ CHNM,,COMAND
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COMAND/ COUNT,,FUNCTION
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Right half of COMAND
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0=> Hang until all tape motions finish
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1=> Rewind
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2=> Rewind and unload (also shreds tape leader)
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3=> Write EOR. Writes out current system buffers even if
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less than record size and writes an EOR gap.
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4=> Write 3 inches of blank tape
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5=> Write EOF. (Two EOF's are written automatically
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after a close on a channel open for writing.)
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6=> Space forward COUNT records. COUNT=0 implies 1
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record. COUNT negative implies space reverse. Stops
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at EOF or BOT.
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7=> Space forward +- COUNT files. (Stops at BOT or
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logical EOT.)
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8.=> Space forward to logical EOT, back up over second
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EOF.
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9.=> Stop and reset the tape system.
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10.=> Set write record size to COUNT words.
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11.=> Read into AC write record size or size of last record
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gobbled by an input IOT.
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Skips if successful.
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Rewind and space only if open for reading.
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Write EOR, 3 inch, EOF writing only.
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Stop and hang for both read and write.
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Transport State Notes
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--------- ----- -----
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A transport turned off or off line is equivalent to not being there.
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Tape can not be written unless the write enable ring is in the hub
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of the tape.
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A transport can be opened by an arbitrary number of channels in
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different modes, but can not be opened by more than one user, or in
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both input and output. The device dependent bits (3.4-4.9) must be
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the same for all channels with the exception of chunk mode.
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The logical end of tape (EOT) is located after two EOF's in a
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row. A close on a channel open for writing writes two EOF's and
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then backspaces over one of them. The .MTAPE command to go to
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the end of the tape also backspaces over the second EOF.
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If the physical end of tape mark is reached while writing a record,
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the record is finished being output (there is always room for a few
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records after the reflective strip) and an IOC error is raised
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saying End of Tape.
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