COLLEGE OF ARTS, SCIENCES AND TECHNOLOGY
Experiment Number: Laboratory No. 1
Experiment Title:
Name:
Subject/ Section:
Date Performed:
Date Submitted:
Instructor Name:
Introduction to Assembly Language Programming Tools
Marc Aeron T. Apolinar
Computer Architecture and Organization Lab
April 5, 2021
April 7, 2021
Mr. Julius Bancud
I.
II.
III.
IV.
Presentation :
Test Data:
Analysis and Conclusion:
Answer to Questions:
Remarks:
____________________________________________________________________________________
__________________________________________________________________________________
Instructor Signature: _________________
LABORATORY NO. 1
Introduction to Assembly Language Programming Tools
I. Objective
To introduce the following assembly language programming tools:
• DEBUG
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.
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.
• 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 t
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.
Its format is :
- N <drive name:> <filename> <extension name>
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
IV. Procedure
DEBUG Environment
1. Types DEBUG at the command prompt of DOS then press ENTER key.
2. Command: R
A. You will see a dash “-“ prompt that signifies DEBUG environment. Type R/r on this prompt
then ENTER key. Illustrate the output:
AX=0000 BX=0000 CX=0000 DX=0000 SP=FFFE BP=0000 SI=0000 DI=0000
DS=072A ES=072A SS=072A CS=072A IP=0100 NV UP EI NG NZ NA PO NC
072A:0100 C3
RET
B. Type the following commands. Write the contents or observation on the space provided:
REGISTER
COMMAND
CONTENTS/OBSERVATION
IP
-
R IP
IP 0100
CX
-
R CX
CX 0000
AX
-
R AX
AX 0000
DH
-
R DH
It shows an error
C. Write the appropriate command to modify the contents of the following registers.
REGISTER
COMMAND
CONTENTS/OBSERVATION
AX
0001
It shows an error but under the error there
is 072A:0100.
CX
0021
It shows an error
IP
0100
It shows an error
3. Command: A
Assemble the given program at the starting offset address 100h. Type A 100 then ENTER
key.
CS:0100 MOV AX, 1
MOV BX, 2
MOV CX, 3
ADD AX, BX
ADD AX, CX
INT 3
4. 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
MACHINE CODE
MOV AX, 01
B90300
MOV CX, 3
01DB
ADD AX, BX
0001
5. Command: G
A. Execute the program in number 3. Type the given command
Command: –g =0100
B. What are the contents of the following registers?
AX
BX
CX
00006
0002
0003
6. Command: T
A. Reset the values of AX, BX and CX and set value of IP to 0100.
B. Execute program given in number 3 using trace command.
C. Type T or t at the DEBUG prompt, then press ENTER key. Repeat this step until all
instructions are executed.
D. What are the contents of the following registers after executing each instruction?
INSTRCUTION
AX
BX
CX
MOV AX, 1
0001
0000
0000
MOV BX, 2
0001
0002
0000
MOV CX, 3
0001
0002
0003
ADD AX, BX
0003
0002
0003
ADD AX,CX
0006
0002
0003
7. Command: D
A. Illustrate or describe the output after executing the following D commands:
COMMAND
D 100 10F
OUTPUT
C3 01 00 BB 02 00 B9 03-00 01 D8 01 C8 00 00 00
D CX: 110 120
60 10 00 F0 60 10 00 F0-80 11 00 F0 60 10 00 F0
60
B. Type in the command: ___D_______
No. of bytes displayed:
128
Beginning Address: ___072A:0100___________
Ending Address:
072A:0170
8. Command: F
A. Determine the contents of the following blocks of memory, after executing the commands.
You may use the D command to display the contents:
COMMAND
BLOCK OF MEMORY
DATA CONTENTS
- F 100 10F FF
100 – 10F
FF FF FF FF FF FF FF FF-FF FF FF FF FF FF FF FF
- F 100 L20 00 FF
100 – 11F
00 FF 00 FF 00 FF-00 FF 00 FF 00 FF 00 FF 00 FF
B. Fill the following blocks of memory with the specified data. Write the appropriate command.
BLOCK
MEMORY
OF DATA
COMMAND
100 - 110
00
00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00
00
11F - 130
00, 01, 10, 11
00
(ALTERNATELY)
01 10 11 00 01 10 11 00-01 10 11 00 01 10 11 00
01
9. Command: E
A. Enter the data ‘John Snith’ at starting address 100h:
What is the command? -E 0100 ‘John Snith’
B. Modify the data ‘John Snith’ to ‘John Smith’ (ASCII code of m=6D)
What is the command? -E 106 6D ______________________________________
V. PROBLEM SOLVING
1) Trace the given code below using DEBUG. Write the contents of AX and flag registers on the space
provided. Verify the result by computing it manually.
INSTRCUTION
AX
FLAG REGISTER
MOV AX, 1234H
1234
NU UP EI NG NZ NA PO NC
ADD AX, 5678H
68AC
NU UP EI PL NZ NA PE NC
ADC AX, 9BCH
7268
NV UP EI PL NZ AC PO NC
INT 3
7268
NV UP EI PL NZ AC PO NC
2) Assume that the program listed below is to be stored in the memory starting at address CS:0500.
Assemble the program below.
MOV AX, 0500
MOV DS, AX
MOV SI, 0100
MOV DI, 0120
MOV CX, 0020
MOV AL, [SI]
MOV [DI], AL
INC SI
INC DI
DEC CX
JNZ 050E
NOP
Execute the program and trace each program and observe the contents of the registers and the memory
locations used.
Conclusion: I conclude that debug helps you to change and monitor your programs
execution by using different kinds of debug. Aside from that Debug allows you to
examine and alter memory. Then by doing this experiment you can manipulate your
registers, like ax and bx etc. Debug uses hexadecimal for you to execute your program.
Furthermore, by displaying your addresses, I conclude that by typing the command, the
address offset will show, the content and the left corner will show your ascii code.