[SOS?]
 Why did I parse that as Son Of Stopgap? 
Because you're wierd? :)
Maybe you confused one strange program with another.
If you work for XKL then you may have used SOS (the editor).  I never have,
but I think I saw a mode diagram in an RT-11 manual (e.g., "Push these keys
when you're in mode X to get to mode Y").  My reaction was, "Oh sh*t, this
is
like a maze!".  At least DEC repented and wrote EDT.  In many ways EDT is a
really good, well-designed program.  I sorta like vi too, though. :)
_Do_ you work for XKL?  I thought you were a student (like me).
-- Derek