The origin of qscan

I was looking through the early posts on this group and found this one
by Cambell Fraser: http://groups.google.com/group/rec.games.corewar/browse_thread/thread/...7d3900d
which includes this little snippet:

>It's possible scan (2x-1) locations in x cycles with the following -
>START cmp <A, <B
> jmp ...
> cmp <C, <D
> jmp ...
> cmp <E, <F
> :
> jmz START, <POS
>
>The main compromise involved is the linear nature of the scans.

That was posted on June 5, 1992, before I started playing corewars on
the web. I suspect that no one picked up on it for the reason that
most programs at that time were quite short, or used fast boots to
eject themselves from large decoys. At that time there was no good
reason for a large, slow program. Until the spiral.

The early imp spirals were launched with code that was sometimes long,
sometimes short, but always required lots of cycles to generate the
processes. That opened the opportunity for a one-time 2c scanner
capable of catching them in the act. Thus was born QuickFreeze the
first quick-scanner. Launching and scanning code have since evolved
together and I doubt that either would be where it is today without
the other driving it. For one thing, if a modern 4-5 line spiral pump
had been introduced in the early days of quick-scanners it might have
been so successful at eluding the scan as to discourage further
development. There are other ways to kill big imps.

Nowadays almost every program does a qscan which has become a way to
boost scores by exchanging wins with other qscanners. So far no one
has found a way to cheat, to score the wins without the losses. If
that happens...

All the best!

P. Kline