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From: arnold@ucsfcgl.UUCP (Ken Arnold%CGL)
Newsgroups: net.lang
Subject: Turing the first?
Message-ID: <428@ucsfcgl.UUCP>
Date: Mon, 28-Jan-85 01:15:06 EST
Article-I.D.: ucsfcgl.428
Posted: Mon Jan 28 01:15:06 1985
Date-Received: Tue, 29-Jan-85 07:08:20 EST
References: <8900018@uiucdcsb.UUCP> <18218@lanl.ARPA>
Reply-To: arnold@ucsfcgl.UUCP (PUT YOUR NAME HERE)
Organization: UCSF Computer Graphics Lab
Lines: 69
Summary: 

<We don't need no steenking bug line!>

(I'm not sure this is the right news group, but I can't think of a
better.  I'm sure at least seven people will think of at least twelve
better ones, though.)

So that you don't have to wait until the end to decide whether you
care, I am herewith nominating Alan Turing for "World's First Hacker".
No, no, NO, I am NOT re-opening the question of whether "hacker" is a
good or bad term.  I just think that (either way) he is the first
person who fits this term in computer programming.

I have been reading the latest biography of Alan Turing ("Alan Turing:
The Enigma"; Andrew Hodges; Simon & Schuster).  I came across the
following section in the description of Turing's creation of ACE, one
of the first digital computers, and (as you shall see) the first in one
rather unusual aspect.

	Alan set out a way in which conditional branching could be done
	without needing the logical control to hold more than one
	'address' at a time.  It was not the best technical solution,
	but it had the merit of a brutal simplicity.  Suppose that it
	were wished to execute instruction 50 if some digit D were 1,
	and to execute instruction 33 it it were 0.  His idea was to
	'pretend that the instructions were really numbers and
	calculate D x (Instruction 50) + (1 - D) x (Instruction 33)'
	The result of this calculation would be a instruction which
	would have the effect that was required.  The 'IF' was effected
	not by hardware, but by programming.  It was a device which had
	led him to mix up data ... with instructions.  This in itself
	was of great significance, for he had allowed himself to
	*modify the stored program* [original emphasis].

An explanation follows of Van Neumann's machine which allowed program
modification only to step through a list of numbers.

	The Turing approach was very different.  Commenting on this
	feature of modifying instructions, he wrote in the report:
	'This gives the machine the possibility of constructing its own
	orders ... This can be very powerful.'

	... He dwelt in particular upon the question of doing
	arithmetic in floating-point form, and showed how the mere
	addition of two floating-point numbers required for a while
	instruction table [program].  He wrote some tables of this
	kind.  MULTIP, for instance, would have the effect of
	multiplying two numbers which had been encoded and stored in
	floating-point form, encoding and storing the result.  His
	tables made use of the 'very powerful' feature of the machine,
	for he had it assemble bits of the necessary instructions for
	itself, and the execute them.

Turing, it would seem, invented self-modifying code, the hacker's best
friend.  Now, admittedly he was working on a mercury loop memory storage
system with all sorts of memory limitations we wouldn't wish on a
toaster oven, and he surely needed this kind of flexibility, but this
seems to be the first creation of a tool no self-respecting hacker
would be without.  In the history of computing, can anyone think of an
earlier person whose creations make them proper holders of this label?

By the bye, I have been generally quite impressed with this book,
although its detail is quite overwhelming at times.  It's been
certainly worth my time; it might be worth yours.
-- 

		Ken Arnold
=================================================================
Of COURSE we can implement your algorithm.  We've got this Turing
machine emulator...