2

Is there a reason that the default value of fill-column is 70?

In my experience, everyone who cares about the value of fill-column prefers a default value of 80.

5

This may have been intended for plain text emails, which get quoted in replies by adding a character (usually >) and often a space at the beginning of each line. 70 columns allow 8 levels of quoting on an 80-column terminal (8 > plus a space plus the rightmost column is reserved for a continuation character to indicate that the line overflows). Back in the days of physical terminals, 80 columns was a de facto standard.

Dominique wrote:
> Charlie wrote:
>> Bob wrote:
>>> Alice wrote:
>>>> I'm first!
>>> Second.
>> Third.
> Fourth.

Fifth.

-- 
Eve

I don't know for sure, however. I don't have a reference. It may well be that the column width dates back from before this email convention. But 80 columns was a very common terminal width even before Emacs existed, so 70 can't come from that alone.

The GNU coding standards requests a width of 79 characters (that's relevant to fill-column for string literals and comments), but that was added much later than the choice of the default value of fill-column in Emacs.

  • 2
    Hollerith (aka punch) cards had/have 80 columns. For some languages (e.g. Fortran) the last several columns were reserved for comments. 80 columns is older than terminal widths - it is older than terminals... – Drew Oct 12 '17 at 22:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.