SA

Stack automata.

A one-way stack automaton ([1], [2]) (here abbreviated as sa) can be thought of as a type of restricted nondeterministic Turing machine. The SA has the power to write or erase only at the right end of the non-blank portion of its storage tape. The storage tape is called a stack, and the blank immediately to the right of the rightmost nonblank symbol is called the top of stack. The SA also has the power to move its stack head (storage tape head) into the nonblank portion of the stack in a read only mode. On each move of the SA, the input head either moves right or remains stationary.

— Sets Accepted by One-Way Stack Automata Are Context Sensitive, 1968