PDA to Turing machine conversion

Question

I have to convert a given PDA into Turing machine form, and am struggling to find any resources on how to do this. If someone could explain or point me to some resource that could explain how to do that it would be much appreciated.

Answer 1

As Welbog suggests in comments, just use the tape like a stack:

1. when the PDA would have pushed onto the stack:

   • leave the current tape symbol alone
   • move the tape head to the right
   • write the symbol to the tape and stay in the same position

2. when the PDA would have popped from the stack:

   • replace the current symbol with blank
   • move the tape head to the left

Notice that this construction means that every "push" transition in your PDA will need an extra intermediate state in the TM to handle the two-step move-then-write operation. There are different ways you could structure this so possibly you could have the extra step on the pop operation instead.