The document describes the stack and stack operations in an x86 architecture. It explains that a stack is a Last In, First Out (LIFO) data structure located in the stack segment of memory. It shows how push and pop operations modify the stack pointer (SP) to add/remove data. It provides examples of subroutines using call and ret instructions, and examples of code that perform additions of data from the stack.

1. -

2. –

3. stack
LIFO
Last
In
First
Out

4. 000F
000E
000D
000C
000B
000A 10h
(stack
segment)
SS
SS

5. 000F 12h
000E 34h
000D 00h
000C 7Fh
000B
000A

6. 000F
000E
000D
000C
000B
000A
F

7. bos
000F 12h
000E 34h
000D 00h
tos
000C 7Fh –
000B –
000A
7Fh - 1234h
SP –
SP
10h
000Ch

9. push
PUSH opnd
SP
-
-

10. pop
POP opnd
SP
-
- – - '

11. (stack
over/underflow)

12. -
•
•
•
•

13. label:
•
•
-
•
ret

14. -
CALL label
label -

15. call
call •
IP
IP •
•

16. ret -
call
ret
IP
end -

17. -‫א‬
AL- AH
AH
AL-
-‫ב‬

18. -
.1
.2
.3

19. .model small
.stack 100h
.data
.code
begin: mov ax, @data
mov ds , as
mov ah,[50h]
mov bh,[51h]
mov ch,[52h]
mov dh,[53h]
call add_numbers
sof: mov ah,4ch
Int 21h
add_numbers: mov dl, 0 -
add dl, ah
add dl, bh
add dl, ch
add dl, dh
ret
end

20. .model small
.stack 100h
.data
.code
mov ax, @data
mov ds , as
begin: call add_numbers
sof: mov ah,4ch
Int 21h
add_numbers: mov ah,[50h] -
mov bh,[51h]
mov ch,[52h]
mov dh,[53h]
mov dl, 0
add dl, ah
add dl, bh
add dl, ch
add dl, dh
ret
end

21. .model small
.stack 100h
.data
x db 5
y db 10
z db 20
w db 17
sum db 0
.code
mov ax, @data
mov ds , as
begin: call add_numbers
sof: mov ah,4ch
Int 21h
add_numbers: mov ah, 0 -
add ah , x
add ah, y
add ah, z
add ah, w
mov sum, ah
ret
end

22. - •
- •

23. .model small
.stack 100h
.data
.code
mov ax, @data
mov ds , as
begin: mov ah ,0
mov al, [50h]
push ax
mov al, [51h]
push ax
mov al, [52h]
push ax
mov al, [53h]
push ax
call add_numbers
sof: mov ah,4ch
Int 21h
add_numbers: pop bx -
pop ax
pop dx
add dl, al
pop ax
add dl, al
pop ax
add dl, al
push bx
ret
end

24. -
20
50h
-