Power of variants of Turing machines I'm having trouble with this problem as I haven't discovered a good way to determine the power of a Turing machine.  I was under the impression that if a Turing machine can perform the same actions and satifies unrestricted access to unlimited memory they're all pretty much equivalent.  Such as multiple tapes and nondeterministic Turing machines.

I am to determine if a and b are equal, more powerful or less powerful then a single-tape Turing machine.  Where do I start?

a) A Turing Machine that can only make moves to the right and never left.

b) A Turing Machine that can move right one space or move left two spaces.
I was under the impression that if a Turing machine can perform the same actions and satifies unrestricted access to unlimited memory they're all pretty much equivalent. 


Hint 1: So your first step should be to determine whether a and b have, or can obtain, unrestricted access to unlimited memory. 

Hint 2: If yes, then try to emulate the missing pieces of your preferred Turing machine model.

Hint 3: If no, then try to show that the halting problem (with empty tape as input) is decidable.