of such “matching pairs” and began selecting them as its source for repeat
requests from the Scheduler, ignoring the others.
Lost along with the original “How to Make a Fred” subfiles were the subsubfiles
on “Programs to Write into a Fred to Start It Up after You’ve Made It.” To make
up for the deficiency, the Supervisor copied through to the Scheduler the full
set of programs that it found already existing in the Freds selected to provide
reproduction information, and these programs, of course, included the ones on
how to make Freds. Thus the robots began coming off the line with one-half of
their “genetic” information automatically built in, and a cycle asserted itself
whereby they in turn became the source of information to be recombined later for
producing more Freds. The method worked, and the Supervisor never figured out
that it could have saved itself a lot of trouble by storing the blueprints away
once and for all in the factory databank.
The program segments being recombined in this way frequently failed to copy
faithfully, and the “genomes” formed from them were seldom identical, some
having portions of code omitted while others had portions duplicated.
Consequently Freds started taking on strange shapes and behaving in strange
ways.
Some didn’t exhibit any behavior at all but simply fell over or failed during
test, to be broken down into parts again and recycled. A lot were like that.
Some, from the earlier phase, were genetically incomplete —”sterile” —and never
called upon by the Supervisor to furnish reproductive data. They lasted until
they broke down or wore out, and then became extinct.
Some reproduced passively, i.e., by transmitting their half-subfiles to the
factory when the Scheduler asked for them.
A few, however, had inherited from the ship’s software the program modules whose
function was to lodge requests with the Scheduler to schedule more models of
their own kind—program modules, moreover, which embodied a self-modifying
priority structure capable of raising the urgency of their requests within the
system until they were serviced. The robots in this category sought to reproduce
actively: They behaved as if they experienced a compulsion to ensure that their
half-subfiles were always included in the Scheduler’s schedule of “Things to
Make Next.”
So when Factory One switched over to mass-production mode, the robots competing
for slots in its product list soon grabbed all of the available memory space and
caused the factory to become dedicated to churning out nothing else. When
Factory Two went into operation under control of programs copied from Factory
One, the same thing happened there. And the same cycle would be propagated to
Factory Three, construction of which had by that time begun.
More factories appeared in a pattern spreading inland from the rocky coastal
shelf. The instability inherent in the original parent software continued to
manifest itself in the copies of copies of copies passed on to later
generations, and the new factories, along with their mixed populations of robot
progeny, diverged further in form and function.
Material resources were scarce almost everywhere, which resulted in the
emergence of competitive pressures that the alien system designers had never
intended. The factory-robot communities that happened to include a balanced mix
of surveyor, procurement, and scavenger robots with “appetites” appropriate to
their factories’ needs, and which enjoyed favorable sites on the surface,
usually managed to survive if not flourish. Factory Ten, for example, occupied
the center of an ancient meteorite crater twelve miles across, where the heat
and shock of the impact had exposed metal-bearing bedrock from below the ice;
Factory Thirteen established itself inside a deep fissure where the ice beneath
was relatively thin, and was able to melt a shaft down to the denser core
material; and Factory Fifteen resorted to nuclear transmutation processes to
build heavier nuclei from lighter ones frozen in solution in the ice crust. But
many were like Factory Nineteen, which began to take shape on an ill-chosen spot
far out on a bleak ice field, and ground to a halt when its deep-drilling robots
and transmutation reactors failed to function, and its supply of vital materials
ran out.
The scavenger and parts-salvaging robots assumed a crucial role in shaping the