Now-a-days we have computers which can show more than 80 characters at a time. "Keep lines fewer than 80 characters", Is this recommendation still valid?
Shorter lines are easier to read. Short lines let you put up several editor windows side by side even on a cramped laptop. Short lines let you use a larger font to save your eyes.
There can also be a code win: when forced to deal with short lines, it's often easier to split a long line of code into two easier to understand lines than it is to split on an operator.
Sometimes a split line is a lot worse than a long line, which is why the rule shouldn't be applied religious -- you should only be called on it if you have many lines over the limit.
IMO, 80 is a little bit tight; I prefer 100. But I wouldn't bike shed it if there was a standard in place.
I really can't stand longer lines, I think that this is a best practice for every code.
I usually work with the monitor splitted in two parts with maybe 2 different files in each half, long lines would make that really difficult to read.
Moreover if you need lines longer than 80 chars you're probably doing it the wrong way: long lines are difficult to understand
I find 80 a bit cramped myself. There are a lot of lovely one-line idioms, like postfix if and iterator blocks, which feel constrained at 80 characters. Worse of all, I spend time worrying about line width.
In principle, having a line width limit is a worthwhile idea. 120 rarely gives me problems, and I can fit 240 characters wide in any case.
Lots of reasons to keep lines sort, though you could argue 80 is pushing it. I've found 100-120 is generally fine for most scenarios on modern hardware.
Just keep in mind that code will be read and shown in a variety of different places. For example reading the code on github or other source control tracking tools, reading it on different terminals with splits active (tmux and VIm splits), etc. Keeping it short just makes it more portable for readability purposes. That's definitely a good thing.
