From https://en.wikipedia.org/wiki/Turing_machine https://en.wikipedia.org/wiki/Turing_machine : "a Turing machine is also equivalent to a two-stack PDA with

From https://en.wikipedia.org/wiki/Turing_machine https://en.wikipedia.org/wiki/Turing_machine : "a Turing machine is also equivalent to a two-stack PDA with standard LIFO semantics, by using one stack to model the tape left of the head and the other stack for the tape to the right." Forth is essentially a two-stack PDA as described.