We really need to get past this smug idea that tech work is uniquely difficult in a way that no one else can understand. Any deep work suffers from interruptions, and programming isn't the only type of work that has significant mental context. This idea that programmers are uniquely vulnerable does no favors when trying to address the problem.
Interrupted work is common to everyone, so use that commonality to your advantage when politely navigating interruptions.
Also, I hope nobody takes the author's fantasy literally:
> Well, worry not, because I think I have a way that you can actually demonstrate to them just how devastating interruptions are to your productivity compared to, say, theirs. In other words, here’s how to make someone understand that, for you, an interruption isn’t just a delay after which you can get right back to work but a complete total of your efforts up to that point. Here’s how. Invite the PM/manager/sales/whatever person to sit at his desk and tell him to humor you. Open up notepad and type a series of 3 or 4 digit numbers in sequence, like so:
Better advice is to learn how to communicate professionally. Real adults don't sit each other down and force them to add up a long list of 3-digit numbers while peppering them with interruptions to make a point.
Instead, communicate like peers: "Sorry, I'm in the middle of something important. Can you come back at lunch time?"
Or: "Is this urgent? I can't really stop what I'm doing right now, but I can stop by your office around 3PM. Will that work?"
Don't be afraid to assert yourself in the conversation. Communicate the concern ("I'm in the middle of something important") and propose an alternative that would work better for you ("Can this wait until lunch time?"). Scale the assertiveness up or down depending on who's interrupting you. We all know some people who will take the hint and disappear, and we all know other people who will try to ignore your concerns and press forward anyway. Adjust accordingly.
Finally - Recovering quickly from interruptions is a skill that can be developed and learned. Obviously, you can't negate the damage of interruptions entirely. However, making an effort to gather your thoughts and return to work after interruptions goes a long way to limiting the damage. The worst thing you can do is pop open HN or Reddit or Twitter after an interruption because you're already out of the groove. Knowing how to manage yourself and get back into the groove as quickly as possible is a valuable skill.