Jabberwock xeno said:
How the hell does this work?
Can you make a computer out of rocks or something then?
Sort of. A computer is built upon the concept of the Turing Machine. To water down a
lot of details, basically one creates an electrical circuit who's properties change depending upon an input. The "rules" of the system, as in the
fundamental rule that governs the operation of a computer is that a given segment can either operate as a wire (it lets current flow) or as a block (it greatly resists electrical flow). Using transistors (tiny devices that can be altered to allow current flow or resist it based upon an input current) one can construct very simple devices that allow for certain fundamental operations. For example AND (if you have current in one line AND current in another line you output current. Otherwise you do not) and OR (if you have current in one line OR another line or even both you output current).
These relatively simple devices are called Turing machines. If one combines large numbers of Turing machines they can do more complex tasks like add a pair of numbers or store information for later retrieval. Once complete, such a system of Turing machines becomes itself, a universal Turing machine. Simply put, given sufficient access to memory and given sufficient time anything that
can be computed can be computed by a universal Turing machine.
Now, because a Turing machine is little more than a device that reads an input and produces an output according to a table of rules, it can take an enormous number of forms. In the simplest form, a person could themselves follow a very simple table of rules to produce such an output and act, themselves, as a Turing machine.