Highly interesting! I’m failing to get any useful search results about that - please throw me a link or two!
Ah, wait, found a table
of ASR 33 mappings, which might help:
(That’s from Appendix 2 of LINC-8 Programming Manual, and shows something a bit like a theta.)
Nearby, the bit pattern index uses a symmetrical boxed minus shape:
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It’s not mentioned as such a whole lot, but here are exactly two references you wished for.
https://www.google.com/search?q=“linc”+“origin+character”+site%3Abitsavers.org
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Ah, thanks, so it’s a character which is used much as an ORG directive in other assemblers.
Just in case, direct links:
A LINC Utility System Technical Report No.1 March 19. 1965
LINC Assembly Program 2 LAP3 May63
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Are we sure that this is the original meaning and reason for the inclusion of this character? Usually, assemblers tend to use whatever is available in the character set. That the character set would have been designed with the assembler in mind, should be quite remarkable.
(However, the character does indeed remind of the common symbol for origin, a stroked circle, and I have no idea why this should have otherwise been deemed important enough to be included.)
No, nothing yet! I’m in contact with one of the UWash St Louis LINC team members, so I’ll ask. But it was probably decided earlier at Lincoln Labs or MIT. Maybe by Mary Allen Wilkes herself.
Assemblers use what is available in the character set, but in this case the character set may have been designed to support the assembler. Or both at the same time. It was largely - almost solely - Wilkes who wrote the software, and the character set was part of that. The characters are defined entirely in software, as a bitmap.
I don’t know to what extent the keyboard was designed for the software, or the other way around. I figure there’s a good chance Wilkes had a say in what symbols went on the keyboard.
I’m guessing this was all decided around 1962 before they team had access to a Teletype. They did later and used it as a printer, but the mapping from LINC characters to ASCII is somewhat awkward. In my opinion, ⊟ would have mapped to @ quite well in both appearance and semantics (“code goes at this location”), but no, they went with $. I see this as an indication that the LINC character set was invented in isolation from ASCII.
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Another interesting oddity are the two quotation marks. There’s the usual upper “ and also the lower „. In the assembler syntax, strings are written as “TEXT GOES HERE„. I understand this is the opposite of what countries with the lower quote usually do: „quote goes here“.
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