🚀 go-pugleaf

     I've got a question concerning some of the line editing provided by
MS-DOS/PC-DOS. 

     In almost every version I used up to and including 3.1, there has
been a Ctrl-U and Ctrl-W keystroke which is recognized.  [For those of
you who didn't know of or didn't have these features, Ctrl-U erases the
entire line (similar to ESC, but on the same line) and Ctrl-W erases
backward to the last non-alphanumeric character]. 

     The one day I was on a friend's machine running DOS 3.1 and found
that his copy did not support either function.  I did some quick
investigating and found that two short jumps in IBMDOS had been NOP'd
out.  I replaced them with the appropriate instructions and everything
worked as it used to [as I was used to]. 

     My question is why was this feature left out in some versions of
DOS (or, why was it included in mine?) I've since looked a little more
closely at the matter and found that the split is just about half and
half between haves and have-nots.  Any reasons? Ideas?

     Thanks.