LAB2

PROGRAM STRUCTURE

The assembly language program consist of code, data and stack.

Data segment: contains all the variable definition.

.DataCode segment: contains a program’s instructions.

.code name (name is optional)

Stack segment: to set aside a block of memory to store the stack

.stack size

PROGRAM STRUCTURE

.MODEL SMALL

.STACK 100H

.DATA; data definition go here

.CODE MAIN PROC;instruction go here MAIN ENDP;other procedures go here END MAIN

PROGRAMMING STEPS

Editor

.ASM File

Assembler

Linker

.OBJ File

.EXE File

Create source program

Assemble source program

Link object program

Q4: Complete the following assembly program:This program should load the value 6438h in AX and the value 9BC8h in BX, then add the two registers and store the result in CX.

A) Write the assembly program in notepad++ and save it as PGM7.asm

Q4:

.MODEL SMALL

.STACK 100H

.CODE

MAIN PROC

MOV AX, 6438h ; Store 6438h in AX

MOV BX, 9BC8h ; Store 9BC8h in BX

ADD AX,BX ; Adding AX and BX

MOV CX,AX ; Store the result in CX

;DOS Exit

MOV AH,4CH

INT 21H

MAIN ENDP

END MAIN

Q4: Use the usual steps to run the program, then using the DEBUG program, follow and answer the following:

How to use DEBUG :C:\ DEBUG PGM7.EXE

    1. Display the register by write command –R2. What are the content of AX , BX, CX and DX registers at the beginning ?3. Trace Instructions by typing –T.4. After each instruction, write down the changes in registers and the values

of the flags (refer to the table below). 5. When you reach INT 21h, press: P, after that complete tracing using T

command.6. Finally exit the DEBUG by typing -Q

Q4:

Display the register by write command –R

What are the content of AX , BX, CX and DX registers at the beginning ?

Next instruction

Q4: Trace Instructions by typing –T.After each instruction, write down the changes in registers and the values of

the flags (refer to the table below).

Addition result Addition affects on flags 1 1 1 1

8 3 4 6+ 8 C B 9

0 0 0 0

FLAGS SYMBOL SET (1) SET (0)

OVERFLOW FLAG OF OV NV

DIRECTION FLAG DF DN UP

INTERRUPT FLAG IF EI DI

SIGN FLAG SF NG PL

ZERO FLAG ZF ZR NZ

AUXILIARY FLAG AF AC NA

PARITY FLAG PF PE PO

CARRY FLAG CF CY NC

TRAP FLAG TF

Q4: When you reach INT 21h, press: P, after that complete tracing using T

command.Finally if you want to exit the DEBUG, type :Q