[nanolith]

On my 4K monitor, I use 4-5 vertical splits and 2-3 horizontal splits. The 80 column rule makes each of these splits readable, and allows me to see the full context of a chunk of kernel code or firmware at once. It has nothing to do with "modern" hardware or "modern" IDEs. It has everything to do with fitting the most amount of relevant information that I can on the screen at once, in context, and properly formatted for reading.

The 80 column rule may seem arbitrary, but it really helps analysis. I avoid open source code that ignores it, and I'll ding code that violates it during code review.

If I had code marching off the screen, or rudely wrapped around so it violated spacing, I'd have to reduce the number of splits I used to see it, and that directly impacts my ability to see code in context. Modern IDEs don't reduce the need to see things in context. It's not a matter of organizing things in drop-down menus, smart tabs, font changes, or magic "refactor" commands. Verifying function contracts in most extant software -- which lacks modern tooling like model checking -- requires verifying these things by hand until these contracts can be codified by static assertions. This, in turn, requires examining function calls often 5-6 calls deep to ensure that the de facto specifications being built up don't miss assumptions made in code deep in the bowels of under-documented libraries. I'd be terribly upset if I had to try to do this in code that not only missed modern tooling but that was written by a developer who mistakenly believed that "80 columns is for geezers." I freely admit that, at 43, I probably count as a "geezer" to many young developers. But, that doesn't change the utility of this rule. Violations of contracts in software account for a large percentage of errors in software AND security vulnerabilities. Most of these violations are subtle and easy to miss unless you can see the call stack in context. No developer can keep hundreds of details from code that they did not write in their head with perfect clarity. It's incredibly nice to have uniform style and uniform maximum line lengths. By convention, 80 columns has shown itself to be the most stable of these limits.

Even FAANG companies like Google follow this rule.

[kllrnohj]

> Even FAANG companies like Google follow this rule.

Google also uses 100

[nanolith]

Most of their monorepo code I came across used 80 columns. But, I can't speak for all of it. Google has a LOT of code.

Either way, if Google and other companies can do what they do in 80 columns, I think it's a fair constraint. What we get out of this constraint is the ability to put a lot of context on the screen.