.....--
INTELLIGENT PROGRAMS
EMBEDDED PATTERN MATCHER
LISP
COMPILER OR INTERPRETER
MACHINE INSTRUCTIONS
REGISTfRS AND DATA PATHS
FLIP FLOPS AND GATES
TRANSISTORS--
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---FIGURE 59. To create intelligent pro-
grams, one needs to build up a series of
levels of hardware and software, so that one
is spared the agony of seeing everything only
on the lowest level. Descriptions of a single
process on different levels will sound very
different from each other, only the top one
being sufficiently chunked that it is com-
prehensible to us. [Adapted from P. H.
Winston, Artificial Intelligence (Reading,
Mass.: Addison-Wesley, 1977).]can be reached. Between the machine language level and the level where
true intelligence will be reached, I am convinced there will lie perhaps
another dozen (or even several dozen:) layers, each new layer building on
and extending the flexibilities of the layer below. What they will be like we
can hardly dream of now ...
The Paranoid and the Operating SystemThe similarity of all levels in a computer system can lead to some strange
level-mixing experiences. I once watched a couple of friends-both com-
puter novices-playing with the program "PARRY" on a terminal. PARRY
is a rather infamous program which simulates a paranoid in an extremely
rudimentary way, by spitting out canned phrases in English chosen from a
wide repertoire; its plausibility is due to its ability to tell which of its stock
phrases might sound reasonable in response to English sentences typed to
it by a human.
At one point, the response time got very sluggish-PARRY was taking
very long to reply-and I explained to my friends that this was probably
because of the heavy load on the time-sharing system. I told them they
could find out how many users were logged on, by typing a special "con-
trol" character which would go directly to the operating system, and would
be unseen by PARRY. One of my friends pushed the control character. In a
flash, some internal data about the operating system's status overwrote
some of PARRY's words on the screen. PARRY knew nothing of this: it is a
program with "knowledge" only of horse racing and bookies-not operat-
ing systems and terminals and special control characters. But to my friends,
both PARRY and the operating system were just "the computer"-a mys-
terious, remote, amorphous entity that responded to them when they
typed. And so it made perfect sense when one of them blithely typed, in
English, "Why are you overtyping what's on the screen?" The idea that
PARRY could know nothing about the operating system it was running
(^300) Levels of Description, and Computer Systems