A long-ass time ago I had a big heavy laser printer that was well documented. It only had a parallel (LPT) port (to give an idea of the age). The documentation gave various control codes that could be sent to the printer. I vaguely recall sending plain text to the port and controlling things like font size using the control codes that were specified in the printer manual. I suppose that was a driver-free mode of operation.

Some LaTeX doc talks about how to produce a DVI file with printer control codes inserted wherever you want. So imagine if you have a cover letter followed by a document you intend to enclose with the letter. You would not generally want the first page of the document to print on the backside of the cover letter, but you might still want the doc to use full duplex mode. In principle, you could have the lp command send it in simplex mode but inject a control character that switches to duplex mode after the first page.

Of course you can inject a deliberately blank page but that’s sloppy. The digital version should have no blanks and the printed version should have blanks in certain places. The \cleartooddpage command is good for the latter but the former. I suppose the caveat is PDFs are disadvantaged and likely cannot handle printer control signals the way DVI can.

Printer manuals apparently no longer acknowledge the existence of control codes. So have we lost a capability because manufacturers insist on dumbing everything down for the stupid masses?

What about driverless printers? The CUPS docs mention that CUPS will become driverless. I really hope that does not mean CUPS is going to obsolete my current driver-dependent printer. But in any case, does driverless imply that there will be a standard for controlling printers, so e.g. we can send a signal mid-printjob to switch to full duplex?