Commonly used in depth-first searching algorithms and pushdown automata, this data structure is almost universally used to store information about function nesting. It also comes in handy when using reverse polish notation, as any character that is read can be compared to the symbol at the top of this data structure; if there is a match, the symbol can be removed. For 10 points—name this last-in-first out data structure, from which an object can 
Commonly used in depth-first searching algorithms and pushdown automata, this data structure is almost universally used to store information about function nesting. It also comes in handy when using reverse polish notation, as any character that is read can be compared to the symbol at the top of this data structure; if there is a match, the symbol can be removed. For 10 points—name this last-in-first out data structure, from which an object can be popped or onto which an object may be pushed.
Commonly used in depth-first searching algorithms and pushdown automata, this data structure is almost universally used to store information about function nesting.
{stack}