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A86 assembler package V3.22 January 25, 1990
The entire package is Copyright 1986--1990 Eric Isaacson.
All rights reserved.
PLEASE read Chapter 1 for legal terms and conditions, how to
register for the package, and the overview of the assembler.
This manual is huge! A note about printing it occurs at
the bottom of the next page.
If you have never heard of "shareware", and you purchased
this disk from XYZ Software House, that advertises great
software for $5 per disk, you may now be asking the following
QUESTION: "What's going on here? Have I already bought an
assembler, or what?"
ANSWER: Well, no, not exactly. You've bought a disk that has
great software on it; you haven't bought the software yet.
A86, like the vast majority of software offered by the $5-
per-disk distribution houses, is free-distribution software
(also known as "shareware", or "user-supported software").
That means I retain the rights to A86, but I choose to let
people pass it around. I have no business relationship
with any distribution houses in the U.S.; I don't get a
penny of the $5 (or whatever) you paid them for the disk
containing A86. So I need and expect to be paid by you,
because I make my living out of making and supporting
shareware products.
A few distribution houses do a pretty poor job of revealing
the shareware nature of the software they sell. If you
thought you had purchased the software free and clear, you
might feel justified in being angry with them for having
misled you. And you might look around for houses that do a
better job of informing the public. But I hope you'll take
the time to consider everybody's role in the shareware
marketing scene; if you do, I think you'll conclude that
although you may have been misled, you haven't really been
cheated out of anything.
Shareware is great for authors like me, who have spent all
their years in their computer holes, learning to be great
programmers, and no time in business school learning
marketing and distribution techniques. We simply cast our
programs to the winds. They are distributed at practically
no cost to us. That's why we can charge less than
the cost of "commercial" software.
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Shareware is also great for customers like you. You can
try out the software before paying for it. You'll know
that a successful shareware product is good, because only
satisfied customers pay for it. The existence of shareware
infuses healthy competition in the entire software market,
for both price and quality. In the case of A86, I'm
utterly convinced that you'll never find a better value for
an assembler, anywhere.
Finally, let's consider the distribution houses. They
provide a legitimate service, for which they charge a
reasonable price. The best houses act as librarians,
evaluating and cataloguing software. Most pay thousands of
dollars for advertising. Their cut is far less than the
distributor's cut for "commercial" software (they prosper
because their volume is bigger). Most customers for the
distribution houses are repeat customers, who are aware of,
and happy with, what they are getting. If it weren't for
your XYZ House, you might never have heard of A86, or might
never have figured out where to obtain it.
So I hope you'll be happy with shareware, and actively
desire to support it. You'll feel good about promoting a
healthy situation for everybody. And you'll encourage the
best programmers in the world to keep writing for you,
instead of for the big corporations.
Now that I've said that, let's move on to the package. The
A86 package consists of the four programs A86.COM, XREF.COM,
EXMAC.COM, and FAKE.EXE; a collection of source, batch, and
library files used by the demonstration contained in Chapter
2, and a sequence of DOC files that, when printed out in
order, make the manual. Each chapter is a DOC file whose
name is A??.DOC, where ?? runs from 00 though 17. Exception:
chapter 6 is split into A06A.DOC and A06B.DOC. The second
file is wider, and should be printed at 12 cpi if you can
manage it. The other files can print at 10cpi with margins--
You should set your printer to a 1-inch left margin, as the
DOC files do not attempt to provide a left margin for you.
(You can modify the PAGE.8 program to output the appropriate
codes!)
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TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION AND LEGAL TERMS
Introduction 1-1
Legal Terms and Conditions 1-1
Registration Benefits 1-3
Overview of A86 1-4
About the Author 1-6
How to Contact Me 1-6
CHAPTER 2 A86 DEMONSTRATION
Demonstration of A86 and Associated Tools 2-1
Assembling a Very Short Program: PAGE.COM 2-1
Demonstration of Error-Reporting 2-1
Assembling a Longer Program with Library Files: REV.COM 2-1
Using XREF on a medium-sized program: TCOLS.COM 2-2
Using EXMAC 2-2
CHAPTER 3 OPERATION AND REQUIREMENTS
Creating Programs to Assemble 3-1
Program Invocation 3-1
Assembler Switches 3-2
The A86 Environment Variable 3-4
Using Standard Input as a Command Tail 3-5
Strategies for Source File Maintenance 3-6
System Requirements for A86 3-6
CHAPTER 4 ELEMENTS OF THE A86 LANGUAGE
The A86 Language and the A86 Program 4-1
General Categories of A86 Elements 4-1
Operand Typing and Code Generation 4-3
Registers 4-3
Variables 4-3
Labels 4-4
Constants 4-4
Generating Opcodes from General Purpose Mnemonics 4-4
CHAPTER 5 SOME EXCLUSIVE FEATURES OF A86
The IF Statement 5-1
Multiple operands to PUSH, POP, INC, DEC 5-1
Conditional Return Instructions 5-2
A86 extensions to the MOV and XCHG instructions 5-2
Local Symbols 5-3
Operands to AAM and AAD Instructions 5-4
Single-Operand Forms of the TEST Instruction 5-4
Optimized LEA Instruction 5-4
0-4
CHAPTER 6 THE 86 INSTRUCTION SET
Effective Addresses 6-1
Segmentation and Effective Addresses 6-2
Effective Use of Effective Addresses 6-3
Encoding of Effective Addresses 6-4
Table of Effective Address byte values 6-5
How to Read the Instruction Set Chart 6-6
The Instruction Set Chart 6-8
CHAPTER 7 THE FLOATING-POINT PROCESSOR
The 8087 and 287 Coprocessors 7-1
Extra Coprocessor Support 7-2
Emulating the 8087 by Software 7-2
The Floating Point Stack 7-3
Floating Point Initializations 7-3
Built-In Constant Names 7-4
Special Immediate FLD Form 7-4
Floating Point Operand Types 7-5
Operand Choices in A86 7-6
The 87 Instruction Set 7-6
CHAPTER 8 NUMBERS AND EXPRESSIONS
Numbers and Bases 8-1
The RADIX Directive 8-2
Floating-point Initializations 8-3
Overview of Expressions 8-3
Types of Expression Operands 8-4
Numbers and Label Addresses 8-4
Variables 8-4
Index Expressions 8-4
Arithmetic Operators 8-4
HIGH/LOW 8-4
BY 8-5
Addition (combination) 8-5
Subtraction 8-6
Multiplication and Division 8-6
Shifting Operators 8-6
Logical Operators 8-7
Boolean Negation Operator 8-7
Relational Operators 8-8
String Comparison Operators 8-8
Attribute Operators/Specifiers 8-9
B,W,D,Q,T Memory Variable Specifiers 8-9
SHORT and LONG operators 8-9
OFFSET operator 8-10
NEAR Operator 8-11
Square Brackets Operator 8-11
Colon Operator 8-11
ST Operator 8-12
TYPE Operator 8-12
THIS and $ Specifiers 8-12
Operator Precedence 8-13
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CHAPTER 9 DIRECTIVES IN A86
Segments in A86 9-1
CODE ENDS and DATA ENDS Statements 9-2
The ORG Directive 9-2
The EVEN Directive 9-3
Data Allocation Using DB, DW, DD, DQ, and DT 9-3
The STRUC Directive 9-6
Forward References 9-6
Forward References in Expressions 9-7
The EQU Directive 9-8
Equates to Built-In Symbols 9-9
The NIL Prefix 9-9
Interrupt Equates 9-9
Duplicate Definitions 9-9
The = Directive 9-10
The PROC Directive 9-10
The ENDP Directive 9-11
The LABEL Directive 9-11
CHAPTER 10 RELOCATION AND LINKAGE
.OBJ Production Made Easy 10-1
Overview of Relocation and Linkage 10-3
The NAME Directive 10-5
The PUBLIC Directive 10-5
The EXTRN Directive 10-6
MAIN: The Starting Location for a Program 10-7
The END Directive 10-7
The SEGMENT Directive 10-8
DATA SEGMENT, STRUC and CODE SEGMENT Directives 10-11
The ENDS Directive 10-11
Default Outer SEGMENT 10-12
The GROUP Directive 10-12
The SEG Operator 10-13
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CHAPTER 11 MACROS AND CONDITIONAL ASSEMBLY
Macro Facility 11-1
Simple Macro Syntax 11-1
Formatting in macro definitions and calls 11-2
Macro operand substitution 11-2
Quoted-string operands 11-3
Looping by operands in macros 11-4
The #L last operator and indefinite repeats 11-5
Character-loops 11-5
The "B"-before and "A"-after operators 11-6
Multiple-increments within loops 11-6
Negative R-loops 11-7
Nesting of loops in macros 11-8
Implied closing of loops 11-8
Passing Operands by Value 11-8
Passing Operand Size 11-8
Generating the Number of an Operand 11-9
Parenthesized Operand Numbers 11-9
Exiting from the Middle of a Macro 11-10
Local labels in macros 11-10
Debugging macro expansions 11-11
Conditional Assembly 11-11
Conditional Assembly and Macros 11-13
Simulating MASM's Conditional Assembly Constructs 11-14
Conditional Assembly and the XREF Program 11-14
Declaring Variables in the Assembler Invocation 11-14
Null Invocation Variable Names 11-15
Changing Values of Invocation Variables 11-15
CHAPTER 12 COMPATIBILITY WITH OTHER ASSEMBLERS
Conversion of MASM programs to A86 12-1
Compatibility-symbols recognized by A86 12-4
Conversion of A86 Programs to Intel/IBM/MASM 12-5
CHAPTER 13 ASSOCIATED TOOLS
XREF Cross-reference and Symbol Listing Facility 13-1
EXMAC Macro Expansion Tool 13-2
A86LIB Source File Library Tool 13-3
Using A86.LIB in A86 Assemblies 13-4
Environment Variable A86LIB 13-5
Forcing a Library Search 13-5
Listings with A86 13-5
Mimicking Tool: FAKE.EXE 13-7
CHAPTER 14 DESCRIPTIONS OF A86 ERROR MESSAGES
CHAPTER 15 RELEASE HISTORY OF A86
CHAPTER 16 RESERVED SYMBOLS IN THE A86 LANGUAGE
INDEX