You should have the whole context comfortably within view, which means all the characters in the lines above and below should be in the same 10 degree visual bl

You should have the whole context comfortably within view, which means all the characters in the lines above and below should be in the same 10 degree visual block, i.e. about 80 characters. The exact value of 80 characters might be because of IBM punched cards, but that value was chosen because printed media already had that limit, or a smaller limit, e.g. broadsheet newspaper columns. People have been writing that way for millennia. Two other points: (1) 70 or 90 might have been acceptable alternatives, but 80 was chosen. It's approximate. Fewer limits the amount of information per line, and more limits the font size you need to scan comfortably. A wider screen allow you to open up several windows. Having one big window isn't such a good idea. (2) I have never been bothered by this limit, except when others break it and I have to read their code. Occasionally, sticking to it requires some thought regarding program layout. If you find yourself exceeding 80 columns often, you're probably doing something wrong. You might be nesting your code too deeply when you could call a function which handles some of your conditional logic, or your function names are too long, which suggests the underlying functions are doing too much and should be split up.