Mobile automata. Substitution systems. Turing machines. Where will the madness end?
As I go deeper into the Book, the expanse of Wolfram's knowledge becomes evident. Now he's taking the most simple of programing systems and showing how the patterns emerge from them. This doesn't always happen. He notes on page 57 that only about fourteen percent of cellular automata show complicated patterns. But oh those patterns. With three hundred steps they can start looking like the conclusion to 2001: A SPACE ODDESSY. He also finds 256 rules for cellular automata.
But he proceeds on to mobile automata, which allows for different rules. Instead of parallel cells, now only one at a time is active. This allows for 65,536 rules. Most don't look promising. Then it's time for "Turing Machines" a theorectical computer system developed by the tragic Alan Turing prior to WW2. Turing could see the promised land, but he was never able to reach it. I like Wolfram's use of the "switches" used in Turing Machines.
Substitution systems are organized so the cell number can change. In a branching system, such as a shrub, this can be quite interesting. Then he moves on to "Tag Systems," where the cell from one end of a line can go the opposite side of the next. I'm really having a difficult time understanding this one, and the cellular notation is starting to cause me to see spots. Once again, he can find "nesting" in some of these programs.
Again: the point he's trying to make is that it is possible to produce behavior of great complexity with very simple programs.
I have reached the section on "Register Machines." I'm trying to absorb it all.