Turing machines

I’ve been thinking about Turing machines a lot, and doing some reading about them. The basic explanation, if I can remember it: there’s a machine that can read this paper tape (probably mylar if it was invented now). The tape looks sort of like a piece of movie film or something, and each square can hold a 1 or a 0. The machine can also move the tape left or right, to read another square. The machine has in internal state, which is basically like one memory location that holds a number. The machine is also constructed to follow a ruleset. The ruleset is a bunch of if-then statements that distate tape movement and the storage of new items on the tape. So, “if the tape says 0 and the current state is 20, change the current state to 27, write a 1 in this position, and move the tape left”

What the hell does all this mean? Turing designed this thing (on paper) in 1936 as the solution to a problem about designing a machine that could solve any mathematical problem without being physically rebuilt or modified. This seems pretty stupid if you’ve got a pentium on your desk, but back then, it was a big deal. And if you’ve ever worked with assembly language, you know the similarities between a Turing machine and a simple (i.e. non-Intel) processor. A Turing machine is sort of like a one-register RISC processor, except it addresses a bunch of paper tape instead of a bus.

Turing killed himself in 1954 because he was a homosexual and the government persecuted him, took away his top secret clearance to work on crypto-stuff for the govt, and forced him to take estrogen injections. At Lindley hall, all of the laserprinters in the basement are named after famous computer scientists. The one named after Turing was always breaking down, more than the others. Coincidence?


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