Table Of ContentSTRUCTURED
ASSEMBLERL ANGUAGE
FOR IBM
MICROCOMPUTERS
Alton R. Kindred
IHIIB3]
Harcourt Brace Jovanovich, Publishers
and its subsidiary, Academic Press
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Copyright© 1991 by Harcourt Brace Jovanovich, Inc.
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ISBN: 0-15-584072-X
Library of Congress Catalog Number: 90-82254
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Turbo Pascal is a trademark of Borland International, Inc.
Microsoft, MS-DOS, and CodeView are registered trademarks of Microsoft
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Machines Corporation.
PREFACE
Most students are first introduced to computer programming through
high-level languages, such as BASIC, Pascal, or COBOL. These languages are
designed to simplify the student's task of expressing a problem to be solved.
Yet, these languages are far removed from the machine language in which
the computer must be instructed to do its work. High-level languages com
monly are used for most application programming. Thus, both in their aca
demic work and subsequent jobs most students will be concerned primarily
with high-level languages. So you might well ask, 'Why study assembler
language?"
REASONSF OR STUDYING ASSEMBLERL ANGUAGE
Assembler language provides a number of benefits to the student, re
gardless of the eventual language in which programming is actually done. In
more than 25 years of teaching I have observed that those students who are
familiar with assembler language learn other languages faster and perform
far better than those who have not learned assembler. Some of these benefits
include the following:
1. A knowledge of the internal functions of the machine that utilizes
assembler language.
2. An awareness of alternate choices of instructions to accomplish various
operations.
3. A better understanding of how the functions of high-level languages are
converted to specific machine instructions.
4. An ability to write subprograms for special purposes not available in
high-level languages.
5. A detailed understanding of address modification, register operations,
and other functions common to many languages.
6. An ability to diagnose object code and analyze core dumps in
debugging.
7. An ability to implement an understanding of the hardware features of
one machine as a basis for studying the capabilities of other machines.
iii
iv PREFACE
FEATURES OF THIS TEXTBOOK
This book is aimed primarily at the college-level student. It meets most of
the objectives of the CS 3 course in ACM Curriculum '78. However, its pace
and abundant examples make it understandable to anyone familiar with one
of the high-level languages, such as BASIC or Pascal. Access to a computer
compatible with the IBM PC or PS /2 is important.
The book employs many techniques to design and write correct pro
grams. Structured programming is demonstrated and practiced throughout.
Initially, program design is shown in flowchart form, pseudocode, and as
sembler language. Later, the flowcharts are eliminated and pseudocode ap
pears as comments in the assembler source statements.
Each type of program structure-sequence, repetition, and selection-is
clearly identified by the use of names such as IF, THEN, ELSE, ENDIF,
WHILE, WEND, REPEAT, and UNTIL. Consistent use of these names helps
to ensure proper structure.
Programs begin with simple input/ output operations involving charac
ter data and gradually move on to arithmetic, number conversions, binary
arithmetic, address modification, and table handling. Later chapters deal
with subprograms, advanced arithmetic operations, macro definitions, link
ing assembler language programs to other languages, and control of the
video screen for monochrome and color adapters.
Data types and machine instructions are introduced only as needed and
immediately utilized in examples and sample programs. Detailed summaries
are presented in the appendices.
Instructions are included not only for the original 8088 processor but for
the newer 80186, 80286, and 80386 processors.
ORGANIZATION OF THE TEXTBOOK
I recommend that the 14 chapters in the book be studied in the sequence
they are presented. However, certain chapters may be omitted or taken in a
different sequence if desired.
Chapter 1 presents fundamental computer terminology, functions, and
concepts and treats binary and hexadecimal arithmetic operations. It also
introduces DEBUG as a tool for examining main storage and analyzing the
execution of instructions.
Chapter 2 explains the roles of the assembler, linker, and EXE2BIN pro
gram and shows the differences between COM and EXE programs. It de
scribes the organization and purpose of each program segment and explains
the types of statements that appear in assembler language.
Chapter 3 presents both DOS and BIOS interrupts for input/ output
operations and for handling the screen display.
PREFACE v
Chapter 4 introduces the structured programming conventions to be
used with assembler language and shows how to implement the program
logic through the use of conditional branching. Nested structures and com
pound conditions are included.
Chapter 5 covers arithmetic and logical operations and presents useful
routines to convert data entered as characters from the keyboard to numeric
form for internal operations. Then it shows how to convert binary numbers
back to character form for display on the screen.
Chapter 6 discusses operation of the stack and both internal and external
subroutines. A library of useful subroutines is created and placed in a library
for use throughout the rest of the book.
Chapter 7 presents the different addressing modes and demonstrates
address modification for processing strings and tables.
Chapter 8 covers advanced techniques for doing arithmetic on multiple
words and converting long strings of digits from the keyboard into multiple
words in storage. Binary-coded decimal operations are also presented.
Chapter 9 presents the string handling instructions with the direction
flag and repeat prefixes. The sample program uses the bubble sort technique.
Chapter covers disk file operations using DOS interrupts. Data organiza
tion with structures and records is also presented. ·
Chapter 11 demonstrates macro definitions, repeat blocks, equates, and
conditional assembly. A useful library of macros is furnished. The sample
program presents the insertion sort technique.
Chapter 12 contains many advanced assembler control features and di
rectives not treated elsewhere in the text. It also presents the new simplified
segment definitions introduced with MASM 5.0 by Microsoft, Inc.
Chapter 13 shows how assembler language routines may be linked to
other languages. Two programs are presented for each of four languages:
Pascal, FORTRAN, BASIC, and C. Parameters are passed from the programs
in each language to an assembler language routine, and results are returned
to the calling program.
Chapter 14 covers BIOS interrupts that service the video display
screen, as well as placement of data and attributes directly into video
memory. Sample programs provide work with both monochrome and
color/ graphics adapters.
Appendices include answers to exercises; the complete list of ASCII
codes; instruction summaries for the 8088, 80186, 80286, and 80386 proces
sors; flag settings; all directives available in the MASM 5.0 assembler; refer
ence information for EDLIN, DEBUG and DOS; and a glossary.
Each chapter contains a statement of objectives, numerous illustrations,
and one or more complete illustrative programs. Each chapter ends with a
summary, review questions, exercises, and lab programming problems.
All programs in the text have been tested using MS-DOS 3.20 and
MASM5.0.
vi PREFACE
SUPPLEMENTAML ATERIALS
An Instructor's Manual is available with teaching suggestions and a
large bank of test questions. The test questions and answers are also available
on disk with software to produce tests to the instructor's specifications. Also
available is a program disk giving source statements and executable files of
all demonstration programs in the book Macros and subroutines shown in
the text have been grouped into libraries for easier use.
ACKNOWLEDGMENTS
Many people have contributed to the development and production of
this book Students in my classes of various assembler languages over 28
years have provided a means of testing the approach used here, particularly
the use of pseudocode in comments to facilitate structured programming.
And my colleagues at Manatee Community College have offered countless
examples and suggestions.
Richard J. Bonacci, of Harcourt Brace Jovanovich, oversaw the develop
ment of the book from its outset with constant encouragement and careful
review. Lynn Edwards provided meticulous editing and guided the transi
tion of manuscript to finished textbook.
The manuscript in its several stages of development was reviewed by
Bohdan Stryk, DeVry Institute, Phoenix; Donald Gustafson, Texas Tech Uni
versity; Jim Leone, Canisius College; Martin Kaliski, California State Poly
technic University, San Luis Obispo; John D. Meinke, Allentown College of
St. Francis de Sales; Russell C. Hollingsworth, Tarrant County Community
College; Walter Chesbro, Santa Rosa Junior College; Al Clare, Youngstown
State, Youngstown, Ohio; Raymond Bell, University of Texas, El Paso; and
David Miller, Bemidji State University. I am grateful for the numerous sug
gestions that came out of their own classroom needs and experiences.
Throughout the entire project, my devoted wife, Joy, has remained a
constant source of inspiration and encouragement, and to her I am deeply
grateful.
Alton R. Kindred
CONTENTS
COMPUTERF UNDAMENTALS 1
1
The Computer System 1
Hardware 2
Memory 2
The 8086 / 8088 Processors 4
The 80286 Processor 7
The 80386 Processor 8
Secondary Storage 8
Input/Output Devices 8
Software 10
The Operating System 10
Application Programs 11
Data Codes 11
ASCII Codes 11
Binary Numbers 12
Hexadecimal Numbers 17
Exploring DEBUG 19
Hexadecimal Addition and Subtraction 19
Examining and Modifying Registers 20
Memory Dumps 21
Program 1 Assembling and Tracing a Short Program 21
Entering Machine Language Directly 24
Saving and Loading Programs 25
Summary 26
Questions 28
Exercises 28
Lab Problems 29
GETTINGS TARTEDI N ASSEMBLERL ANGUAGE 31
2
Overview of the Assembly Process 31
Types of Statements 32
Instructions 33
Directives 34
Macros 34
Comments 34
Defining Segments 34
The Code Segment 35
The Data Segment 36
The Stack Segment 37
COM versus EXE Programs 38
COM Programs 38
EXE Programs 40
vii
viii CONTENTS
Program 2A COM Program to Print Four-Line Name and Address
Program Description and Comments 41 ·
The Segment 43
Writing the Source Program 45
Assembling the Program 45
Locating and Removing Errors 47
Linking the Program 48
Executing EXE2BIN 51
Executing the Program 52
Program 2B EXE Program to Print Four-Line Name and Address 52
Summary 55
Questions 55
Exercises 56
Lab Problems 57
INTERRUPTS 58
3
Overview of Interrupts 58
Hardware Interrupts 59
DOS Function Interrupts 60
·Keyboard Input Functions 61
Screen Output Functions 63
The Printer Function 64
Other Functions 64
BIOS Function Interrupts 65
Cursor and Display Handling Functions 65
Other BIOS Functions 67
Program 3 DOS and BIOS Interrupts 67
Summary 68
Questions 73
Exercises 73
Lab Problems 74
PROGRAM LOGIC AND CONTROL 75
4
Program Structures 75
Sequence Structure 77
Repetition Structures 77
Selection Structures 78
Comparison 82
Conditional Jumps 84
Conditional Jumps after Comparison 85
Conditional Jumps after Other Instructions 85
Unconditional Jumps 85 ·
Writing Structures in Assembler Language 88
Simple Structures 88 ·
Nested Structures 90
Compound Conditions 91
Special Looping Instructions 92
Program 4 Demonstration of Structures 93
Summary 96
CONTENTS ix
Questions 97
Exercises 98
Lab Problems 98
ARITHMETICO PERATIONS 99
5
Negative Numbers 99
The Add, Subtract, and Negate Instructions 100
Incrementing and Decrementing 101
Multiplication 102
Division 103
Logical Operations 104
AND 105
OR 106
XOR 106
NOT 106
TEST 107
Shifting and Rotating 107
Shifting 108
Rotating 109
Converting Numbers to Printable Characters 110
Displaying Hex Digits 111
Displaying DecimalDigits 113
Converting Character Digits to Numbers 114
Converting Hex Characters to Numbers 114
Converting Decimal Characters to Numbers 116
Program 5 Numeric Conversions 117
Summary 121
Questions 122
Exercises 123
Lab Problems 124
SUBROUTINESA ND THE STACK 125
6
Stack Operations 125
Subroutines 127
Near Subroutines 127
Far Subroutines 128
The PUBLIC Statement 128
The EXTRN Statement 128
Placing Subroutines 129
Passing Parameters 143
Using Registers 143
Using Flags . 144
Using Memory Locations 144
Using the Stack _1 45
Program 6 Using External Subroutines 146
Summary 149
Questions 150
Exercises 151
Lab Problems 151
