... reproduction1
Also often called simply replication''.
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... tape);2
This is as von Neumann formulated his design, but it may be noted that nothing important hangs on the constructor having this double functionality; the tape copying could be mediated by completely separate machinery, or even no machinery at all, without materially affecting any of the analysis which follows.
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... phenotype.3
Of course, this encoding must be relative to the particular decoding implemented by the parental constructor. We will return to this point shortly.
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... unlimited.4
Admittedly, this ease of interaction actually makes the problem of realising quasi-quiescence'' rather harder--because any given program entity can effectively disrupt any other. This seriously constrained evolutionary phenomena in earlier systems of this sort, such as the -universes (McMullin, 1992; Holland, 1976) or Coreworld (Rasmussen et al., 1990). Perhaps the most important innovation in the development of Tierra was the introduction of memory protection'' which allowed for control of such interactions.
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