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GROUP EVALUATION FORM
Laboratory 1: Introduction to Assembly Language Programming Tools
Group No:
Section:
LAB SCHEDULE:
Group Members:
DATE PERFORMED:
1.
DATE SUBMITTED:
2.
Exercises
3.
Prog’g Problems
4.
Teamwork (+pts)
5
EVALUATION GRADE:
EVALUATION: (for lab instructor use only)
Exercises (50%):
Prog’g Problems (50%):
Lab Performance (10%):
Attendance (10%):
LABORATORY NO. 1
Introduction to Assembly Language Programming Tools
I. Objective
To introduce the following assembly language programming tools:
 DEBUG
 Netwide Assembler (NASM)
 Emulator 8086 (EMU8086)
II. Components to be borrowed
 PC power cords (2)
 Keyboard (1)
 Mouse (1)
III. Conceptual Framework
A. DEBUG is a program included in the MS-DOS and PC-DOS operating systems that allows the programmer to monitor
program’s execution closely for debugging purposes. Specifically, it can be used to examine and alter the contents of
memory to enter and run programs, and to stop programs at certain points in order to check or even change data.
Figure 1 shows the DEBUG environment.
FLAGS
Figure 1. DEBUG Environment
Commands in DEBUG
1.1 Entering and exiting DEBUG
 To enter the DEBUG program, simply type its name at the DOS level:
A :\> DEBUG<return>

After DEBUG and enter key (carriage return) have been entered, the DEBUG prompt “-“ will appear on the
following line. DEBUG is now waiting for you to type in a command.
To exit Debug, simply type Q (quit command) after the DEBUG prompt:
- Q <return>
After the Q and enter key (carriage return) have been entered, DEBUG will return you to the DOS level.
1.2 Examining and altering the contents of registers
 R, the REGISTER command. The register (R) command allows you to examine and/or alter the contents of the
internal registers of the CPU. The R command has the following syntax:
- R <register name>
The R command will display all registers unless the optional <register name> field is entered, in this case only
register named will be displayed and/or altered.
1.3 Coding and running programs in DEBUG
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
A, the ASSEMBLE command. The assemble command is used to enter assembly language instructions into
memory.
- A <starting address>

The starting address may be given as an offset number, in which case it is assumed to be an offset into the
code segment, or the segment register can be specified explicitly.
U, the UNASSEMBLE command. The unassembled command displays the machine code in memory along
with their equivalent assembly language instructions. The command can be given in either format shown
below:
- U <starting address> <ending address>
- U <starting address> <L number of bytes>

If the U command is entered with no addresses after it: “U <return>”, then DEBUG will display 32 bytes
beginning at CS:IP.
G, the GO command. The GO command instructs DEBUF to execute the instructions found between the two
given addresses. Its format is:
- G <=starting address> <stop address(es)>

If no addresses are given, DEBUG begins executing instructions at CS:IP until a breakpoint is reached. After
a breakpoint is reached, DEBUG displays the register contents and returns you to the command prompt. Up
to 10 stop addresses can be entered.
DEBUG will stop execution at the first of these breakpoints that it reaches.
T, the TRACE command. The trace command allows you to trace through the execution programs one or
more instructions at a time to verify the effect of the programs on registers and/or data. Its format is:
- T <=starting address> <number of instructions>
The trace command functions similarly to GO command in that if no starting address is specified, it starts at
CS:IP.
1.4 Data Manipulation in DEBUG
 D, the DUMP command. The dump command is used to examine the contents of memory. The syntax of the
D command is as follows:
- D <start address> <end address>
- D < start address> <L number of bytes>

The D command can also be entered by itself, in which case debug will display 128 consecutive bytes
beginning at DS:100.
F, the FILL command. The fill command is used to fill an area of memory with a data item. The syntax of the F
command is as follows:
- F <starting address> <ending address> <data>
- F <starting address> <L number of bytes> <data>

This command is useful in filling a block of memory with data, for example to initialize an area of memory
with zeros.
E, the ENTER command. The enter command can be used to enter a list of data into a certain portion of
memory.
- E <address> <data list>
- E <address>
For example, - E 100 ‘John Smith’. This example showed how to enter ASCII data, which can be enclosed in
either single or double quotes.
1.5 Loading and Writing programs
 N, the NAME command. The name command initializes a filename in memory before using the load and
write commands.
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
Its format is :
- N <drive name:> <filename> <extension name>


B.
After the code has been entered with the A command, CX must be set to contain the number of bytes to be
saved and register BX must be set to 0.
W, the WRITE command. The write command is used to save instructions onto a disk. Its format is:
-W
L, the LOAD command. The load command performs the opposite function of Write command. It loads from
disk into memory starting at the specified address. Its syntax is:
-L
NASM is an acronym for Netwide Assembler, unlike DEBUG that is specifically for debugging purposes, this software
assembles program written in assembly in any platform. NASM Integrated Development Environment (NASMIDE) is
complete software that has an editor, assembler and builder. Figure 2 is the NASMIDE environment.
NASM was among the first
of the Open-Source, freely
available, assemblers
available for the x86. The
project was started in the
1996 time frame as a way
of creating a portable x86
assembler.
* Source: Webster
Figure 2. NASMIDE environment
Note: Use Help option to explore the environment.
NASM Program Structure:
;NASM-IDE ASM Assistant Assembler Project File
BITS 16
;Set code generation to 16 bit mode
ORG 0x0100 ;Set code start address to 0100h
Setting of bit mode and IP
address
section .text
j.tio
MAIN:
jmp START
DISP:
mov ah,09h
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;String Print int service
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Main Program
Data Assignment
C. EMU8086 is an 8086 machine emulator licensed software. It provides a virtual machine to emulate 8086microprocessor system and provides assembly language programming and simulation. Figure 3 shows the EMU8086
environment.
Figure 3. EMU8086 Environment
Emu8086 combines an advanced source editor, assembler, disassembler, software emulator (Virtual PC) with
debugger.
*Source: Help option of Emu8086
IV. Procedure
DEBUG Environment
1.
2.
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Type DEBUG at the command prompt of DOS then press ENTER key.
Command: R
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A. You will see a dash “-“ prompt that signifies DEBUG environment. Type R/r on this prompt then ENTER key.
Illustrate the output:
B. Type the following commands. Write the contents or observation on the space provided:
REGISTER
IP
COMMAND
- R IP
CX
-R CX
AX
- R AX
DH
-R DH
CONTENTS/OBSERVATION
C. Write the appropriate command to modify the contents of the following registers.
3.
REGISTER
AX
NEW CONTENTS
0001
CX
0021
IP
0100
Command: A
Assemble the given program at the starting offset address 100h. Type A 100 then press ENTER key. Encode the
program written below:
CS:0100
4.
COMMAND
MOV AX,1
MOV BX,2
MOV CX,3
ADD AX,BX
ADD AX,CX
INT 3
Command: U
A. Write the command that will unassemble the program in number 3:
Command: __________________________________________
B.
What are the equivalent machine codes of the following instructions?
INSTRUCTION
MOV AX,01
MACHINE CODE
MOV CX,3
ADD AX,BX
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5.
Command: G
A. Execute the program in number 3. Type the given command
Command: –g =0100
B.
6.
A.
B.
C.
D.
What are the contents of the following registers?
AX
BX
CX
Command: T
Reset the values of AX, BX and CX and set value of IP to 0100.
Execute program given in number 3 using trace command.
Type T or t at the DEBUG prompt, then press ENTER key. Repeat this step until all instructions are executed.
What are the contents of the following registers after executing each instruction?
INSTRUCTION
MOV AX,1
AX
BX
CX
MOV BX,2
MOV CX,3
ADD AX,BX
ADD AX,CX
7.
Command: D
A. Illustrate or describe the output after executing the following D commands:
COMMAND
OUTPUT
D 100 10F
D CS:110 120
B.
Type in the command: ___D_______
No. of bytes displayed: ___________
Beginning Address: ______________
Ending Address: ________________
8.
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Command: F
A. Determine the contents of the following blocks of memory, after executing the F commands. You may use the
D command to display the contents:
COMMAND
- F 100 10F FF
BLOCK OF MEMORY
100 – 10F
- F 100 L20 00 FF
100 – 11F
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DATA CONTENTS
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B.
Fill the following blocks of memory with the specified data. Write the appropriate command.
BLOCK OF MEMORY
DATA
COMMAND
100 - 110
00
11F – 130
9.
00,01,10,11
(alternately)
Command: E
A. Enter the data ‘John Snith’ at starting address 100h:
Command: ______________________________________
B.
Modify the data ‘John Snith’ to ‘John Smith’ (ASCII code of m=6D)
Command: ______________________________________
10. Command: N, W, L
A. Assemble the given program at starting address 100h. Write the command on the space provided.
Command: ____________________________________
CS:0100
CS:0103
CS:0106
CS:0108
CS:010A
CS:010B
CS:010C
CS:010E
CS:0111
B.
MOV
MOV
MOV
ADD
INC
DEC
JNZ
MOV
INT
CX,05
BX,0200
AL,0
AL,[BX]
BX
CX
0108
[0205],AL
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Name the file ”LAB1.com” and save it in drive C. Set the value of CX with the total number of bytes of the
program and set BX to 0 before saving. Write the commands for naming and saving the file.
Command (Naming): ____________________________
Command (Saving): _____________________________
Note: Check the file in drive C.
C. Exit from DEBUG and load the saved file (LAB1.com) by typing DEBUG LAB1.com from the DOS prompt. Use
Unassemble command; do you see the program code LAB1.com? ________
NASMIDE Environment
TABLE 1: Translation of C program statements to Assembly codes:
C program statements
Assembly Equivalent codes
printf(“Hello World! /n”)
section
lea
mov
int
.text
dx,[msg1]
ah,09h
21h
section .data
msg1 db ‘Hello World’,13,10,’$’
printf(“%c”, ‘A’)
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section .text
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mov ah,02h
mov dl,’A’
int 21h
scanf(“%d”, num)
section .text
mov ah,01h
int 21h
Note: value of num will be stored at AL
if (x <> 0)
statements here(TRUE)
else
statements here(FALSE)
section .text
cmp al,0
jz TRUE
jmp FALSE
for (i=5;i<>0; i--){
section .text
mov CX,5 ;CX is equal to i
next: nop
:
loop
next
;loop
instruction
decrements CX by 1
then checks if CX
is equal to 0
:
}
i=0;
while(i<=5){
:
i++;
section .text
mov
next:
add
cmp
jle
;al is representing x
al,0
al,1
al,5
next
;al is equal to i
}
main(){
:
section .text
mov ah,4ch
int 21h
} //exit of C
11. Run the NASMIDE software located at c:\NASM. Type NASMIDE at the prompt
C:\NASM\> nasmide
12. Write the code below in NASMIDE editor and save it as printf.asm.
BITS 16
ORG 0x0100
; Display String
[section .text]
j.tio
MAIN:
jmp START
DISP:
mov ah,09h
int 21h
ret
START:
lea dx,[msg]
call DISP
END:
mov ah, 4ch
int 21h
;String Print INT service
;Display
Lab1message
;call DISP subroutine program
;End of program
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13. Run the program (a shortcut key to run the code is CTRL-F9). Illustrate the output on the space provided.
14. Create another code (given below) in NASMIDE editor and save it as scanf.asm.
BITS 16
ORG 0x0100
; Input a number and display
; Author: J. TIO
[section .text]
MAIN:
jmp START
DISP:
mov ah,09h
;string print
int 21h
ret
START:
lea dx,[msg]
call DISP
mov ah,1
;input char
int 21h
;char entered placed to al
END:
mov ah, 4ch
;End of program
int 21h
section .data
msg db “Input a number: ”,”$”
15. Compile and run the program. Illustrate the output on the space provided.
16. Create another code (given below) in NASMIDE editor and save it as if.asm.
j.tio
bits 16
org 0x0100
[section .text]
MAIN:
jmp START
DISP:
mov ah, 09h
int 21h
ret
ONE:
lea dx,[msg2]
call DISP
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c:\NASM\> printf
17. Compile and run the program.
18. Input number 1 then press ENTER key. Repeat this step then input the numbers 2,3 and 4 for each run.
19. Illustrate the outputs on the space provided.
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EMU8086 Environment
20. Invoke EMU8086 software.
21. Click the Samples Icon then choose Hello file.
22. Click Emulate icon, then choose Run icon.
23. Illustrate the output.
24. Close the Emulator, then repeat steps 21 and 22 now choose traffic_lights file. Click Stop icon if you want to stop
running the code. Describe the output.
22. Close the Emulator, then create a new file, choose COM template.
23. Write the given code below and save it as samplecode.asm.
MOV AL, 80H
MOV BL, 80H
ADD AL, BL
MOV AH,4CH
INT 21H
24. Compile and run the code, now is single step. Write you observations on the space provided.
25. Create another code (given below) in EMU8086 editor and save it as string.asm.
#make_COM#
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; COM file is loaded at CS:0100h
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ORG 100h
;string input
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26. Compile and run the program.
27. Input the string “COMSYLA!”. Illustrate the output on the space provided.
V. Programming Problems
1. Trace the given code below using DEBUG. Write the register and flag’s content on the space
provided. Verify the result by computing it manually.
INSTRUCTION
MOV AX,1234h
AX
Flag Register
ADD AX,5678h
ADC AX,9ABCh
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INT 3
*Flag Register Content – refer to figure 1
2. Make an assembly program that will translate decimal values (0 to 15) to its equivalent
hexadecimal code. Use EMU8086.
Example:
Input a number (0 to 15): 15
Equivalent Hex code: F
3. Make an assembly program that will display the equivalent alphanumeric characters of ASCII
codes 41h to 49h using loop. Use NASMIDE.
Example:
Alphanumeric Characters of ASCII values 41h to 49h:
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ABCDEFGHI
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