Studies on optimal code width?

Actually, the 80-column thing long precedes DOS. It comes from card punches, which were 80-column devices.

And to kind of answer the OP's question, one "study" has been going on for about 600 years now - the printed book. These have evolved over the centuries, with readbility foremost in mind, to the position we are at now where the average line length for text is around 60 characters. So for readability, go for narrower margins.

I don't have studies, but I will relate my experience.

I find that horizontal scrolling is tedious when dealing with text. I look at the environment that the code will be used in, and set width standards based on that context.

For example, when I worked in Emacs on XWindows, it worked well to have 2 Emacs windows side-by-side at all times. That limited them to 80 characters, so that was my max line length.

At one point I worked in Visual Studio on a 1920x1200 screen. I'd keep it maximized, with all tool windows docked down one side. There was enough space left for two editor windows side-by-side at around 100 characters.

I also find that the longest lines come from method calls with long parameter lists. This is sometimes a code smell: perhaps the method should be refactored.

If you & your co-programmers have high-resolution screens and sharp eyesight, by all means use a small font and long lines. Conversely, you may need short lines.

Have mercy on the programmers who have to maintain your software later and stick to a limit of 80 characters.

Reasons to prefer 80:

• Readable with a larger font on laptops

• Leaves space for putting two versions side by side for comparison

• Leaves space for navigation views in the IDE

• Prints without arbitrarily breaking lines (also applies to email, web pages, ...)

• Limits the complexity in one line

• Limits indentation which in turn limits complexity of methods / functions

Yes, it should be part of the coding standard.

I normally use 120-150 unless the company describes otherwise. However it depends also on the kind of code:

• I (almost) never use multiple statements on one line
• I only use long lines (>12) only if lines that look similar can be aligned and not broken.
• I always use enough spaces/parenthesis etc
• I prefer longer variables names above shorter names

Until a few years ago I limited to 100 but now widescreens are normally used and high resolution monitors 120 can be even seen on laptops (which I barely use).

Comparing a screen to a book is not really good because a book has more vertical space and a screen has more horizontal space. I always try to keep a function max. one visible screen long.