Cellular Structure.

An individual program (or more precisely, an individual process, which may be serial or parallel) in Cosmos has many more structures associated with it than do programs in Tierra. Tierran programs just have the list of instructions, a program pointer, registers and a stack. In contrast, Cosmos programs also have all of the structures explained in Section 4.3. The idea was that they should incorporate some of the features (e.g. regulators, translation machinery, and areas where new strings may be constructed) observed in cellular biological organisms. The programs must rely largely on communications to interact with the outside world, and cannot directly read the code of their neighbours.