Introduction To Assembly Language Programming

INTRODUCTION TO ASSEMBLY
LANGUAGE PROGRAMMING
Prof. Bhavana K.
Information Technology Department
International Institute of Information Technology, I²IT
www.isquareit.edu.in

International Institute of Information Technology, I²IT, P-14, Rajiv Gandhi Infotech Park, Hinjawadi Phase 1, Pune - 411 057
Phone - +91 20 22933441/2/3 | Website - www.isquareit.edu.in | Email - info@isquareit.edu.in
Assembly Language Programming (ALP)
Structure of ALP Program
Sections in ALP program are:
 Title
 .model
 Data declaration section
 Code section

Structure of ALP Program:

 Title – This assembler directive is used to give title
to a program.
 .model – It initializes memory model.
Tiny Code and Data fit into 64K
Small All data fits in one 64K segment, all code fits in one
64K segment.
medium All data fits in one 64K segment, but code may be
greater than 64K.
compact Data may be greater than 64K , code must be less than
64K.
large Both data and code may be greater than 64K

 Data declaration section:

 Data declaration section:
 DB (Define byte) assembler directive is used to
define byte type of variable
 DW (Define word) assembler directive is used to
define word type of variable.
 To define string
 msg db 10,13,”hello$”
 10– ASCII value for new line
 13– ASCII value for carriage return
 $ is used to indicate end of string
 To define an array of 4 bytes
 array db 10,11,12,13

 Code section
 Initialization of data segment
 MOV AX,@DATA
 MOV DS,AX
 It stores upper four digits of data segment base address in
DS (Data segment ) register.
 The address in DS is used as a segment base address along
with offset address to fetch value from data segment.

 Interrupts used in assembly language:
 To accept single digit
 MOV AH,01
 INT 21H
 Hex ASCII value of accepted digit gets stored in AL
register.
 To display single digit
 MOV DL,HEX_ASCII_VALUE_OF_DIGIT_TO_DISPLAY
 MOV AH,02
 INT 21H
 To terminate program
 MOV AH,4CH
 INT 21H

 Interrupts used in assembly language:
 To display string
 LEA DX,VARIABLE_NAME ; Offset address of string to display
 MOV AH,09
 INT 21H

 Commands to execute program

 Commands to execute program
 TASM FILENAME.ASM
 The input to assembler is .asm file. It generates two
files .obj and .lst
 TLINK FILENAME.OBJ
 Input to linker is .obj file. It generates two files .map
and .exe
 To execute program give FILENAME.EXE on command
prompt.

 To debug ALP program: To check logical errors.
 TD FILENAME.EXE
flags
Stack
segment
Code
segment
Data
segment
registers

References:
1. Peter Abel, Niyaz Nizamuddin, "IBM PC Assembly Language and
Programming", Pearson Education
2. Ray Duncan, "Advanced MS DOS Programming", 2nd edition, BPB
Publications

E-mail – bhavanak@isquareit.edu.in
Website - http://www.isquareit.edu.in/

Introduction To Assembly Language Programming

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