Thank you for creating it! Is there some article or something which talks about the original project or motivation for the DVI format? If DEK implemented it as part of TeX in 1982, what was DVI being used for before that?
Sure. Knuth's original Sail version of TeX just directly wrote output in XGP format, since the only type of usable device anybody had was the experimental XGP printer (which Xerox had bestowed on a few CS departments, years before electrostatic printers were commercially available, never mind laser printers). When Knuth ordered the Alphatype typesetter, he asked me to write a new output module for the required format, and we'd be able to statically link it instead of the XGP module, so there'd be two TeX executables to choose from, depending where your output was going.
Well, imagine you're an unaccomplished grad student, and you're going to tell Prof. Donald Knuth that he's wrong-headed, that his approach wouldn't scale, and that the right thing to do instead is to have a simple, intermediate format, so that nobody would have to muck around in TeX's internals to get a new output device going. Quite the rush when he gave the go-ahead.
So, the first DVI format was purpose-built for proto-TeX (and underwent a revamp for the final cut, just like everything else). It's really just a slightly compressed form of display-list (move to x,y; put down character c in font f; move; put down a rule; done with page) and nothing to write home about. While it was important in the early days to help us and others to get various devices going, and allow for Tom Rokicki's fabulous(ly important) DVI-to-PostScript program, given the ubiquity of PDF today, it's appropriate that we've come full circle, and PDF output is built into most TeXs that people now use, leaving DVI mostly a historical footnote.
Those were good times. I got a copy of the SAIL Metafont and managed to port it to Tandem's TAL language (rather like BLISS, but stack oriented on a 16/32-bit machine). There was some serious bit-twiddling in the code using every bit of every 36-bit word!
Working with TeX (thankfully the Pascal version), we spent lots of time doing DVI implementations for various devices. Are virtual fonts still a thing?
Very interesting. Thank you for filling this gap in my knowledge of historical events. I'm always keen to understand the context in which things like this came about. I take your point about PDF being the dominant format leaving little use for DVI, but intermediate representations are a powerful lever, so I hope DVI remains for a good while yet for people to experiment with.
I believe we used an XGP printer at MIT to print out solicitation letters for a Chorallaries[1] tour in the early '80s. All I remember was that it was a very large device, and was reputed to blow toner into the cable runway under the raised floor.
Thank you for creating it! Is there some article or something which talks about the original project or motivation for the DVI format? If DEK implemented it as part of TeX in 1982, what was DVI being used for before that?
(For those unfamiliar, https://en.wikipedia.org/wiki/Device_independent_file_format)