1. Lab 6
Stack

2. Push & Pop Instructions
PUSH source
POP destination
Last in First Out, First in Last Out
SP initialized to 100H which represent empty stack.
SP might contain offset address. (Stack Not Empty)
PUSH decreases SP by 2
POP increases SP by 2

3. Example 1
Swap contents of CX = 30H and BX=32H, display it before and after swapping
org 100h
MOV CX,30H ;moving contents into registers
MOV BX,32H
MOV AH, ;display first content
MOV DX,CX
INT 21H
MOV AH, ;display second content
MOV DX,BX
MOV AH, ;display newline
LEA DX,NL
PUSH CX ;swapping contents
PUSH BX
POP CX
POP BX
MOV AH, ;display first contents
MOV DX,CX
INT 21H
MOV AH, ;display second contents
MOV DX,BX
ret
NL DB 0DH,0AH,"$"

4. Procedures Invoking procedures: CALL name name PROC ;body of procedure
ret
name ENDP
Invoking procedures:
CALL name

5. INDEC / OUTDEC Input and display it in a new line. org 100h CALL INDEC
MOV BX,AX
MOV AH,9
LEA DX,NL
INT 21H
MOV AX,BX
CALL OUTDEC
ret
NL DB 0DH,0AH,"$"
INCLUDE 'PGM9_1.ASM'
INCLUDE 'PGM9_3.ASM'
END

6. Exercise
Let the user input 2 numbers and display the result of multiplication.

7. Solution org 100h CALL INDEC MOV BX,AX CALL NEWL XOR AX,AX MUL BX
XOR BX,BX
MOV AX,BX
CALL OUTDEC
ret
NL DB 0DH,0AH,"$"
NEWL PROC
MOV AH,9
LEA DX,NL
INT 21H
RET
NEWL ENDP
INCLUDE 'PGM9_1.ASM'
INCLUDE 'PGM9_3.ASM'
END