Basic Dount in PDA functioning

Question

Assume my language is WW^R (Palidromes)

Now when we use PDA for this,we will guess middle everytime.It can be middle or it cant be middle,so a new branch is created everytime.Now each branch will get the current stack picture and starts its operation. So my question is does this branches operates one by one?Because we have one stack only or do we use multiple stacks by replicating the initial contents before a branch starts?

Because each branch will do push/pop according to its need and changes the stack,if that branch fails,we need to proceed further but how single stack is able to manage this scenerio?

Can some one explain this?

Answer 1

A push-down automaton (PDA) is a form of imaginary machine So, we can use multiple stacks by replicating the initial contents before a branch starts and run all machines in parallel.