In a turing machine, what do they mean by "state"?

[h="1"]my book says things like: "The control ele- ment is a device with a finite number of internal "states."" [/h]I am starting to understand how the machine operates but I really dont know what they mean by different states.
We have state Q1 and Q2, etc but what is a state?? The tape is moving along a straight line...what characterizes a different state?

Reply 1

such

A state is like an instruction. It tells the Turing machine what to do with the tape, depending on the symbol that the machine has just read. It then tells the machine what the next instruction (state) it should execute is.

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Reply 2

TheWakeUpCall

I'm a bit rusty on this topic, but I would describe it differently.

You normall talk about states and transitions between states. An instruction is a transition, and the states are where you are between instructions.

You normally think of states and transitions as circles connected by directed arrows. For example the following image: http://introcs.cs.princeton.edu/java/74turing/control+tape1.png

The state you are in determines what actions you can make. Different actions will take you to different states.

Does this make sense?

EDIT: This video might help http://www.youtube.com/watch?v=IkYhfk4X47c

(edited 11 years ago)