having hard time reading symbols in this Turing Machine

Question

I am reading few books and I am looking at different examples of a Turing Machine, and I am getting frustrated reading symbols especially in this example...What does $ symbol mean ? what does E symbol mean, is that null or empty ?...what does the symbol on the far right mean , is that a reject state? thanks!

Answer 1

Some comments:

• It seems that $\varepsilon$ denotes an empty string (some authors use $\lambda$ for that).
• Symbol $\$$ is a frequently used out-of-alphabet symbol, here to mark the end of the stack, i.e. to know when the word should end.
• Symbol $\varnothing$ on the right is most probably "reject state".
• Notation $\varepsilon \to a$ would be then pop nothing and push $a$.
• Simirarly $a \to \varepsilon$ would be pop $a$ and push nothing.
• Reading $\varepsilon$ as an input indicates an $\varepsilon$-move (or silent move), i.e. one without reading input; it's useful for simplifying the automata.

I hope this helps $\ddot\smile$