Provision is made in the main supervisor for internal code input and output with paper tape codes not normally used in the Mathematical Laboratory. Anyone wishing to make use of this facility should. first consult the management for authorization and then a member of the supervisor group to arrange that the necessary tables, see below, are incorporated into the supervisor.
The following notes describe the structure of the supervisor tables which are used for translation to and from internal code; such tables must be prepared for any foreign code used. Only two shift (or, trivially, single shift) codes can be catered for.
There are two tables, one for each shift; the first of these tables is for the shift in which a document is assumed to begin (hereafter called 'first shift') and the shift character into this shift must be the one having value 0.7 in internal code. The second shift table follows immediately after the first shift table. Each entry in the tables consists of a single halfword and the entries are in the natural order i.e. the first entry is for blank tape, the second for the character with only the least significant hole punched, etc.
Each entry contains the internal code value of the character in d0-5 together with marker digits as follows:
|Illegal character or parity fail||J65|
|Carriage control character||J74|
|Character in either set||J6|
|Outer set character||J5|
|Warning sequence character (*-type)||J4|
|Z-type character (can follow ***)||(||J44||first shift|
Illegal characters normally have d0-5 zero
[This entry is a handwritten addition:]
|CCC which can be absorbed into following one||J75|
There are three tables which follow sequentially in the order: inner set, outer set, carriage control table. The entries are again single half-words but the order within each table is as follows:
|0.0 / 0.4|
|1.0 / 1.4|
|7.0 / 7.4|
|0.1 / 0.5|
|7.1 / 7.5|
|0.2 / 0.6|
|7.3 / 7.7|
For the inner set and outer set tables, the entry contains the character value to be punched right-justified to digit 2(i.e. d2 corresponds to the least significant hole), with marker digits as follows:
|Redundant set change||J54|
|Character in either shift||J44|
|Second shift character in inner set||J4|
|First shift character in outer set||J6|
|0.6 in inner set, 0.7 in outer||J74|
|0.6 in outer, 0.7 in inner||J7|
|Inner set change to outer (0.4 in inner)||J5|
|Outer set change to inner (0.5 in outer)||J64|
|Character to be punched twice (e.g. Tab as 2 spaces)||0.1 + other markers (J4, J44, J6)|
Illegal characters are, in general, translated as a decimal point.
In the carriage control table, an unassigned code is represented by a zero half-word; otherwise the entry contains the character, positioned as for the other O/P tables, together with a count in d23-20 (J04 for one, etc.). If the count is to be 100, d17 (J004) should be set. Marker digits are as follows:
|either shift||d18 = 0|
|Character 2.0 needed|
|first d0 = 1|
Two tapes (Titan flexowriter) should be prepared, one containing the input tables and one the output tables; they should each have a title in the form of an IIT comment, giving the name of the code and whether input or output. Each tape should be terminated: newline Z newline stopcode run-out.
In general, complete freedom of translation is allowed but 0.4 - 0.7 should retain their normal meanings, run-out should remain 7.3 inner set and the warning sequence character 1.6 inner set. It is, however, desirable to maintain, as far as possible, compatibility with the normal internal code, especially for inner set characters.
17 November 1966
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: 12. Organizational
Extracodes for Input/Output, B.L., 9 February 1966
Next Planning Document: 14. File Storage and Protection, AGF, August 1966
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