Size of Instruction Set.

The REPLiCa instruction set is about twice as big as that of the Tierran language. Many of the instructions can certainly be removed without having a great impact on the things that programs can do (e.g. the self-replicator listed in Section A.3.1 only uses 17 different instructions). If the genetic code were allowed to evolve, then unused instructions might be expected to be removed from the code by natural selection, allowing common instructions to be represented multiple times.