Re: Shell scripts

[aje9383@osfmail.isc.rit.edu (Andrew Erickson)]

In article <ZgJy4.143$Mom.1048620@dca1-nnrp1.news.digex.net>,
Frank Townsend <ftownsen@iamdigex.net> wrote:
>What is N-Key rollover and phantom key?

"Rollover" is where a keyboard allows one to press a key before the one
previous has been released, generally with the tacit assumption that to
do so does not cause anything strange to happen.  N, in the context, is
the number of keys which one can do this with; on most modern keyboards
and operating systems (which, AFAIK, usually work with separate depress
and release keycodes), N would be the number of keys on the keyboard; a
less modern system might only support 1-key rollover, which isn't rough
to type on; I think the Apple ][ was in that category.  0-key rollover,
however, is a royal PITA.  (I think maybe some of the PETs had no roll-
over, in addition to only having numbers in the numeric keypad.)

The phantom key effect was a side effect of the keyboard decoding which
the Apple ][, at least, used; if too many keys were down, it lost track
of what was going on and inserted additional characters.  Starting with
the //e, a more clever keyboard controller was used which tended not to
do such tricks.

(The //e keyboard was, AFAIK, the first keyboard to have keyboard tits,
on the D and K keys.  IBM later decided to use the F and J keys, making
untold thousands of people type bibdrbduvsk drbyrbvrd,)

-- 
Andrew Erickson