SP

Introduction

The stack is a special linear table, which is a linear table that only allows insert or delete operations at one end of the table. The end of the table that allows insert and delete operations is called the top of the stack. The other end of the table is called the bottom of the stack. The current position of the top of the stack is dynamic, and the mark of the current position of the top of the stack is called the top pointer of the stack. When there are no data elements in the stack, it is called an empty stack. The insertion operation of the stack is usually called stacking or stacking, and the deleting operation of the stack is usually called unstacking or popping.

The stack in the computer is mainly used to store temporary data, local variables and the return address of the interrupt/call subroutine program.

The stack pointer is a special stack pointer (usually called TOP) during the stack operation, indicating the location of the top element of the stack.

The stack pointer always points to the top element of the stack.

The stack can grow downward (towards lower addresses) or grow upward.

If the stack grows upward, when the data is pushed onto the stack, the stack pointer is incremented by 1, and then pushed onto the stack. When popping the stack, the data is first popped and the stack pointer is decremented by one. If the stack grows downward, the pointer will decrease by 1 when the data is pushed onto the stack, and increase by 1 when the data is pushed out of the stack.