Preface

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One 、 What is a stack ？

A stack is a specific storage area or register , One end of it is fixed , The other end is floating . The data stored in this storage area of the heap , It's a special data structure . All data is stored or taken out , Only at the floating end （ Stack top ） Conduct , Strictly in accordance with “ First in, then out ” The principle of access , The element in between , Must be on top of its stack （ Latecomers ） The elements can only be taken out after being removed one by one . In memory （ Ram ） Open up an area in the stack , It's called software stack ; A stack of registers , It's called hardware stack .
brief introduction ：

• A data structure
• The elements in and out of the stack follow ：“ First in, then out ” principle

You must be using high-level languages , for example ：java,c,c++,python And so on have used the stack , Its operation mechanism is generally clear , But the details are still vague .
This article will start from 《 assembly language 》 That is, the lowest point of view of the computer allows you to re understand the stack .

Two 、 Foreword knowledge of stack

mention 《 assembly language 》, It is inevitable to say 14 A register , Pictured （ be based on 8086CPU Of course ）

It is said in the world that ：“ Put this 14 Learn to understand , I graduated from assembly language ” The legend of .
That is, this article talks about stack , Then we need to understand ：

• SS： Stack segment register
• SP： Stack pointer register group
  8086CPU The operation of entering and leaving the stack is based on the word （word） In units . One word （word） Is two bytes （byte）.
  Anytime ,SS:SP Point to the top element of the stack
  Stack is empty ,SS:SP Points to the next unit of the highest address unit in stack space .（ because “ Anytime ,SS:SP Point to the top element of the stack ”, So when the stack is empty, there is no stack top element , therefore SS:SP You can only point to the cell below the bottom cell of the stack .）

3、 ... and 、 Stack operation

1、 Initialization of stack

mov ax,1000H
mov ss,ax	; Set the segment address of the stack ss=1000H, You cannot directly write to the segment register SS Send data , So use ax transit 
mov sp,0010H

2、 Push

mov ax,1234
push ax

Push ax Actually, two operations are performed ：

• SP=SP-2
• take ax Content feed SS:SP In the memory unit pointed to ,SS:SP Now point to the top of the new stack

Storage , follow “ High storage high , Low save low ” Principles .

3、 Out of the stack

Pop bx

pop bx Actually, two operations are performed ：

• take SS:SP The data at the memory unit pointed to is sent to BX in
• SP=SP+2,SS:SP Point to the cell below the top of the current stack （ The new top of the stack ）
  

3、 ... and 、 matters needing attention

• Assembly language is not case sensitive
• When programming, be careful that the top of the stack exceeds the limit ： prevent “ When the stack is full, continue to enter the stack ” and “ When the stack is empty, continue to exit the stack ” The unbounded phenomenon of .
• Stack space is also part of memory space

️️️ Don't forget the romantic duck when you are busy Typing Code ！