Stack

In computer science the term stack refers to a data structure which allows values to be pushed on to the top of it, and allows values to be popped of its top.

Simple computers have a single dedicated computer register, called the "stack pointer", that points at the location in memory where the address of the instruction that called the most recent subroutine.

Since subroutines are designed to be called recursively each instance of a subroutine needs a unique place for its local variables. The stack is useful for setting aside this space.