This document discusses stacks and the push and pop instructions. It defines a stack as a LIFO (last in, first out) data structure. PUSH adds an item to the top of the stack, while POP removes an item from the top. Examples are given showing how data is added and removed from an empty stack using these instructions. The difference between PUSH and POP is explained, and stack register and how it is used to point to the current top of the stack is described.

1. SUBMITTED BY
S.Nandhin
N.S COLLEGE OF ARTS & SCIENC

2. STACK INTRODUCTION
 What is stack ?
 Stack with example
 Push and Pop
 Difference Push and Pop
 Stack register

3. STACK
 The stack is a temporary store data and address
 The CPU may PUSH important data on to the stack
 While it is processing other data

4. What is Stack?
 The stack is a LIFO->LAST IN FIRST OUT
TOP
BOTTOM
5
4
3
2
1
STACK Pointer

5. STACK
 These are important instructions that store and retrieve
data the LIFO stack memory
 They Two main functions:
PUSH
POP
PUSH: Add item to top
POP: Remove item from top

6. STACK EXAMPLE
STACK IS
EMPTY
7
PUSH 7 PUSH 8
7
8

7. STACK Example
EMPTY
STACK
7
POP 8 POP 7

8. STACK INSTRUCTION
NAME
MNEMONICS AND
FORMAT DESCRIPTION
Push onto the stack PUSH SRC (SP) (SP)-2
((SP)+1: (sp))
(SRC)
Pop from the stack POP DST (DST) ((SP)+1:
(SP))
(SP) (SP)+2
Push the flags PUSHF (SP) (SP)-2
((SP)+1 : (SP))
(PSW)
Pop the flags POPF (PSW) ((SP)+1 :
(SP))
(SP) (SP)+2

9. PUSH & POP Definition
 These are important instruction that store and retrieve data the
LIFO Stack memory
 There are SIX Frames of the PUSH and POP
 Instruction,register,memory,immediate,segment register ,flags and all
register
 PUSH: Push op code copies data from the source address to stack.
 POP: Pop op code copies data from the stack to the destination address.

10. PUSH and POP example

11. Difference between PUSH &
POP Key Difference push is when an Entry is“PUSHED “ on to the Stack
 Pop is when the last pushed Entry is “Popped off” the stack
 PUSH & POP FOR EXAMPLE:
 PUSH CX
 PUSH DX
 POP DX
 POP CX

12. STACK REGISTER
o In 8086 main stack register is called Stack pointer (SP)
o The Stack segment register (SS) is usually used to store
information about memory segment
o That stores the call stack of currently Executed
program SP points to current Stack Top.

13. Setting up a Stack by Loading the SS and
Sp register
STACK_SEG EGMENT
DW 30 DUP(?)
TOS LABEL WORD
STACK_SEG ENDS
CODE_SEG SEGMENT
ASSUME CS:CODE SEG, SS:STACK SEG
START : MOV AX,STACK_SEG
MOV SS,AX ;INITIALIZES SS
MOV SP,OFFSET TOS ;INITIALIZES SP
:
:
CODE_SEG ENDS