It's the thing that baffles me the most with those people, the Knuths and Lamports and Carmarcks, and whatnot.

It's not like they have light schedules - they do research, they have classes, they attendconference, and they have jobs, etc...

And some benefit from tenure, which give them time to deeply focus on some topics.

But I can't imagine how I would write tex in ten years in Pascal on archaic machines if I had all the time to myself.

Doing that in the middle of understanding more computer science than my eyes would ever read ?

What do they do with their time ? What do they don't do ? Are they able to skip the eating and pooping and sleeping and cleaning their house and picking up parcels at the post office and grocery shopping parts ?

Or a proto Unix being written in three weeks. Concretely, what are the days of those three weeks made of ? Especially since it's famously when the spouse was NOT there to handle the housekeeping...

I see not amount of "life hacks" and "atomic habits" and whatnot helping with that. But it's probably just as natural to them as biking - and you can't explain biking, I guess ?

A favorite Knuth story to illustrate: He was re-writing the 8080 code for the processor that ran our new Alphatype CRS Phototypesetter, since the manufacturer's code wasn't suitable. Real-time, 7 levels of simultaneous interrupt stuff, since it controlled two stepper motors that moved the lens around the photographic paper, plus four custom font outline-tracing S100 cards that flashed vertical segments of characters at just the right moment on the CRT that the lens then focused onto the paper. No debugability other than a 4x4 keyboard and a 15(?) character display. I was responsible for the code on the other end of the RS232 port that connected it to the DEC mainframe, sending down character outlines on the fly to the very limited memory on the 8080, along with the properly-sorted character placement info ultimately from TeX.

Anyway, we'd been doing morning, noon, and night debugging sessions together for a number of days. On maybe the 3rd morning, I arrived at his office and was speaking with his secretary of many years, Phyllis Winkler, when Knuth came in. He handed her a stack of maybe a dozen or two pages, saying "Here's a paper I wrote; please type it in." When? When did he write it? It's still a mystery to me.