Two-stack encoding of a Turing tape
= Two-stack encoding of a Turing tape
{title2=$c=(q,L,R)$}
Encode the cells immediately left of the head in a reversed positional stack $L$, and the current and right cells in $R$. Quotient and remainder by the alphabet base read and remove cells; multiplication by that base pushes a cell. The resulting local tape transitions are <primitive recursive>, which makes them directly implementable on <Church numerals>.