| 1030 | create input n from data ba |
| 1031 | terminate current input |
| 1032 | ba' = status of input stream n |
| 1040 | create output n from data ba |
| 1041 | terminate current output |
| 1042 | ba' = status of output stream n |
In all the extracodes stream numbers lie in the range 0 ≤ n ≤ 254; the extracodes monitor if n is outside this range or if a clash of stream numbers is generated. The convention is used that C = halfword pointed at by ba, C' = next halfword, etc.
The stream is set up as D-type if n is even, the P-type is n is odd. The source of the stream is specified by the store pointed at by ba, and there are three options:
C = tape logical number t (0 ≤ t ≤ 126)
C'= block number N (1 ≤ N ≤ 4095)
C = J4
C' etc., file title (up to four words)
C = m.1 where m is the mth allowed device.
[Handwritten pencilled note: m = logical device number]
The current input is terminated (monitors if no input selected), and null selection set up (so that further read extracodes monitor). The stream may then be dealt with in one of four ways.
| (1) | Ba = 0, n < 0 | Stream is deleted (subsequent 1050's will monitor) |
| (2) | Ba = 0, 0 ≤ n ≤ 254 | Remainder of stream renamed as n (D if n even, P if n odd) |
| (3) | Ba ≠ 0, 0 ≤ n ≤ 254 | Whole of stream renamed as n (D if n even, P is n odd) |
| (4) | Ba ≠ 0, n < 0 | Whole of stream left for future reselection from the start with same number |
(N.B. (4) is not included in (3)).
[Handwritten pencilled notes on the above: "ONL." to the left; "Same as" by (3), (4) (brace to the left, close parenthesis to the right, of (3), (4)), with arrow pointing to (1), (2); (2) ticked; "Re-initialise input" inserted after (4). I don't know the correct interpretation of these. ]
| (1) | n even | b119' = n, ba' set for stream n as below | ||
| (2) | n odd | b119' = | (n | (even) is n is present |
| (m ( ( | if n is not present where m is the next highest stream present and then ba' is the data for stream m | |||
| (J4 | if no such m | |||
| ba' = 0 | if not present | |||
| .1 if P, .1*4 | if P and never selected | |||
| .2 if D, .2*4 | if D and never selected. | |||
[Handwritten notes:
| d2 = 1 | Tape |
| d21 = 1 | File |
| d20 = 1 | Console |
| d5-3 = console no. (logical) | |
Status marker (8/153) ]
There are four options for the destination of the stream
| (1) | To TAPE: | C = tape number C' = amount est. C" = block number |
| (2) | To FILE: | C = -ve, even C' amount est. C" et seq. = file title (up to 4 words) |
| (3) | To peripheral: | C =
peripheral code + 0.1, + *4 if a stream title is being given +
translation table code in D22-18 (=0 if standard) C' = amount est. C" et seq. = title (if *4 set in C) (up to 4 words; N.B. brackets are not required) C = m.3 if to online device m. |
| (4) | Pending: | C = 0.1, C' = amount est. + options of (3) |
The amount estimate is in blocklets in d0 (equivalently pages in D3). The destination for a pending stream must be set by a subsequent use of 1041 Ba 0 S. Note that the program log appears to the system as output 16, and it is therefore not permissible for the user to select, create or destroy output 16.
In all cases the current record is terminated with carriage control char. 0.0 .
| (a) | D1 = 1 | (D0 arbitrary) current output is terminated and cancelled (as if it was to NONE) |
| (b) | D0 = 1, D1 = 0 | current output is terminated (so that reselection monitors) |
| (c) | D0 = 0, D1 = 0 | current output is broken, so that further output is to the next part of this stream; and the next part is set up according to the data in ba (as in 1040). If Ba = 0 then the destination is set to be to the same peripheral type with the residue of the previous limit and no title, or faults if it is not to a peripheral. |
In cases (b), (c), if the current (part) stream is pending then S points to the destination data (as in 1040) which may not be to TAPE. (But note that if to peripheral, a stream title is not allowed, and if given is ignored.)
If the stream being terminated is to TAPE, then on return to the program b97 is set to the last block used.
The (part) stream is renamed as input N (P type if m has D2 = 1, D otherwise); the stream is broken (as (c) above) if m is even, and terminated (as (b) above) if m is odd. An attempt to rename a stream whose destination is NONE causes a monitor 17.
The treatment of even and odd n is exactly as for the 1032 extracode. The following data is set into ba to give information concerning the stream:
| D0 = 1 | if to tape |
| D1 = 1 | if to file |
| D6-2 | peripheral code (= 0 if tape, file, none, or pending) |
| D7 = 1 | if currently selected as binary |
| D8 = 1 | if output limit has been exceeded for the first time |
| D9 = 1 | if " " " " " second time |
| D10= 1 | if pending |
| D11= 1 | if ever selected |
| D22-18 | translation table code |
| D23= 1 | if exists. |
| [next two entries added in handwriting:] | |
| D12= 1 | if console |
| d5-3 = | logical console no. |
Errors detected in the use of the input parts of these extracodes (1030, 1031, 1041 (2)) cause fault 16, while those in the output parts (1040, 1041 (1)) cause fault 17.
B91 is set to describe the fault, and can take the following values:
| 0 | Unimplemented facility |
| 1 | No stream selected |
| 2 | Stream number out of range |
| 3 | Illegal tape number |
| 4 | Illegal block number |
| 5 | Output estimate too large |
| 6 | Limout exceeded |
| 7 | Peripheral code out of range |
| 8 | Sending 'pending' document to tape |
| 9 | Attempt to cancel a stream being renamed |
| 10 | Stream number clash |
| 11 | Logical tape does not exist |
| 12 | Too many parts in a broken stream |
| 13 | Renaming a 'none' stream. |
9 February 1966 B.L.
Copyright © 1966 University of Cambridge Computer Laboratory. Distributed by permission. Thanks to Barry Landy, Roger Needham and David Hartley for giving permission to distribute these documents. Thanks to Barry Landy for lending me the paper document from which this was scanned. Any typographical errors probably arose in the course of OCR.
Previous Planning Document: 11. The File Dictionary
System: I - General Description, DWB, 11 February 1966 (supersedes
number 6)
Next Planning Document: 13. Input and Output in
Foreign Codes, MFB and BL, 17 November 1966
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