# Legal actions on a PDA and terminology

I am unsure about the following so I would like to verify if my statements are true:

1. We can remove at most a single character ($Z\in\Gamma$) from the PDA (top ?) of the stack with one step of the PDA [I do not know what is the correct terminology]

2. We can add a string of characters $(\alpha\in\Gamma^{*})$ to the (top ?) of the stack with one step with one step of the PDA

I would also appreciate the help with the terminology I lack (that is, should I write top or bottom and how does a single step by the PDA called)

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## 1 Answer

Both your numbered statements are correct for the usual definition of a PDA.

Symbols are always put onto and removed from the top of the stack.

"Step" is the correct word.

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