Contents


Introduction		 xiii
New and Extended Features in MASM 6.1 xiii
MASM Features New Since Version 5.1 xiv
MASM Features New Since Version 6.0 xv
ML and MASM Command Lines xvi
Compatibility with Earlier Versions of MASM xvi
A Word About Instruction Timings xvii
Books for Further Reading xviii
Document Conventions xix
Getting Assistance and Reporting Problems xx

Chapter 1 Understanding Global Concepts		 1
The Processing Environment 1
8086-Based Processors 2
Operating Systems 4
Segmented Architecture 5
Segment Protection 6
Segmented Addressing 7
Segment Arithmetic 7
Language Components of MASM 8
Reserved Words 8
Identifiers 9
Predefined Symbols 10
Integer Constants and Constant Expressions 11
Operators 13
Data Types 14
Registers 16
Statements 21
The Assembly Process 22
Generating and Running Executable Programs 23
Using the OPTION Directive 24
Conditional Directives 28

Chapter 2 Organizing Segments		 31
Physical Memory Segments 32
Logical Segments 32
Using Simplified Segment Directives 33
Defining Basic Attributes with .MODEL 34
Specifying a Processor and Coprocessor 38
Creating a Stack 38
Creating Data Segments 39
Creating Code Segments 40
Starting and Ending Code with .STARTUP and .EXIT 41
Using Full Segment Definitions 44
Defining Segments with the SEGMENT Directive 44
Controlling the Segment Order 47
Setting the ASSUME Directive for Segment Registers 49
Defining Segment Groups 51

Chapter 3 Using Addresses and Pointers		 53
Programming Segmented Addresses 53
Initializing Default Segment Registers 53
Near and Far Addresses 57
Operands 60
Register Operands 61
Immediate Operands 61
Direct Memory Operands 62
Indirect Memory Operands 64
The Program Stack 71
Saving Operands on the Stack 71
Saving Flags on the Stack 73
Saving Registers on the Stack (80186-80486 Only) 74
Accessing Data with Pointers and Addresses 74
Defining Pointer Types with TYPEDEF 75
Defining Register Types with ASSUME 77
Basic Pointer and Address Operations 78

Chapter 4 Defining and Using Simple Data Types		 85
Declaring Integer Variables 85
Allocating Memory for Integer Variables 85
Data Initialization 87
Working with Simple Variables 88
Copying Data 89
Adding and Subtracting Integers 92
Multiplying and Dividing Integers 95
Manipulating Numbers at the Bit Level 98
Logical Instructions 99
Shifting and Rotating Bits 100
Multiplying and Dividing with Shift Instructions 102

Chapter 5 Defining and Using Complex Data Types		 105
Arrays and Strings 105
Declaring and Referencing Arrays 105
Declaring and Initializing Strings 108
Processing Strings 110
Structures and Unions 117
Declaring Structure and Union Types 118
Defining Structure and Union Variables 121
Referencing Structures, Unions, and Fields 126
Nested Structures and Unions 128
Records 129
Declaring Record Types 130
Defining Record Variables 131
Record Operators 133

Chapter 6 Using Floating-Point and Binary Coded Decimal Numbers		 135
Using Floating-Point Numbers 136
Declaring Floating-Point Variables and Constants 136
Storing Numbers in Floating-Point Format 138
Using a Math Coprocessor 139
Coprocessor Architecture 140
Instruction and Operand Formats 141
Coordinating Memory Access 145
Using Coprocessor Instructions 146
Using An Emulator Library 155
Using Binary Coded Decimal Numbers 156
Defining BCD Constants and Variables 157
BCD Calculations on a Coprocessor 157
BCD Calculations on the Main Processor 158

Chapter 7 Controlling Program Flow		 161
Jumps 161
Unconditional Jumps 162
Conditional Jumps 164
Loops 172
Loop-Generating Directives 173
Writing Loop Conditions 178
Procedures 180
Defining Procedures 180
Passing Arguments on the Stack 182
Declaring Parameters with the PROC Directive 184
Using Local Variables 188
Creating Local Variables Automatically 190
Declaring Procedure Prototypes 193
Calling Procedures with INVOKE 194
Generating Prologue and Epilogue Code 198
MS-DOS Interrupts 204
Calling MS-DOS and ROM-BIOS Interrupts 204
Replacing an Interrupt Routine 206

Chapter 8 Sharing Data and Procedures Among Modules and Libraries		 211
Selecting Data-Sharing Methods 211
Sharing Symbols with Include Files 212
Organizing Modules 212
Declaring Symbols Public and External 214
Positioning External Declarations 228
Using Alternatives to Include Files 219
PUBLIC and EXTERN 220
Other Alternatives 221
Developing Libraries 221
Associating Libraries with Modules 222
Using EXTERN with Library Routines 223

Chapter 9 Using Macros		 225
Text Macros 226
Macro Procedures 226
Creating Macro Procedures 227
Passing Arguments to Macros 228
Specifying Required and Default Parameters 229
Defining Local Symbols in Macros 232
Assembly-Time Variables and Macro Operators 233
Text Delimiters and the Literal-Character Operator 234
Expansion Operator 235
Substitution Operator 237
Defining Repeat Blocks with Loop Directives 239
REPEAT Loops 240
WHILE Loops 241
FOR Loops and Variable-Length Parameters 242
FORC Loops 244
String Directives and Predefined Functions 245
Returning Values with Macro Functions 248
Returning Values with EXITM 248
Using Macro Functions with Variable-Length Parameter Lists 249
Expansion Operator in Macro Functions 251
Advanced Macro Techniques 251
Defining Macros within Macros 251
Testing for Argument Type and Environment 252
Using Recursive Macros 255

Chapter 10 Writing a Dynamic-Link Library For Windows		 257
Overview of DLLs 257
Loading a DLL 258
Building a DLL 260
DLL Code 261
DLL Data 265
DLL Stack 265
DLL Extension Names 266
Summary 266
Example of a DLL: SYSINFO 267
Entry Routine for SYSINFO 268
Expanding SYSINFO 270

Chapter 11 Writing Memory-Resident Software		 273
Terminate-and-Stay-Resident Programs 273
Structure of a TSR 274
Passive TSRs 274
Active TSRs 275
Interrupt Handlers in Active TSRs 275
Auditing Hardware Events for TSR Requests 275
Monitoring System Status 277
Determining Whether to Invoke the TSR 279
Example of a Simple TSR: ALARM 279
Using MS-DOS in Active TSRs 285
Understanding MS-DOS Stacks 285
Determining MS-DOS Activity 285
Interrupting MS-DOS Functions 286
Monitoring the Critical Error Flag 287
Preventing Interference 288
Trapping Errors 288
Preserving an Existing Condition 289
Preserving Existing Data 290
Communicating Through the Multiplex Interrupt 290
The Multiplex Handler 291
Using the Multiplex Interrupt Under MS-DOS Version 2.x 292
Deinstalling a TSR 292
Example of an Advanced TSR: SNAP 293
Building SNAP.EXE 294
Outline of SNAP 295

Chapter 12 Mixed-Language Programming 		307
Naming and Calling Conventions 308
Naming Conventions 309
The C Calling Convention 309
The Pascal Calling Convention 310
The STDCALL and SYSCALL Calling Conventions 311
Writing an Assembly Procedure For a Mixed-Language Program 312
The MASM/High-Level-Language Interface 313
The C/MASM Interface 315
The C++/MASM Interface 322
The FORTRAN/MASM Interface 323
The Basic/MASM Interface 328

Chapter 13 Writing 32-Bit Applications		 335
32-Bit Memory Addressing 335
MASM Directives for 32-Bit Programming 336
Sample Program 337

Appendixes


Appendix A Differences Between MASM 6.1 and 5.1		 341
New Features of Version 6.1 342
The Assembler, Environment, and Utilities 342
Segment Management 343
Data Types 344
Procedures, Loops, and Jumps 347
Simplifying Multiple-Module Projects 348
Expanded State Control 349
New Processor Instructions 350
Renamed Directives 350
Macro Enhancements 351
MASM 6.1 Programming Practices 352
Compatibility Between MASM 5.1 and 6.1 352
Rewriting Code for Compatibility 353
Using the OPTION Directive 361
Changes to Instruction Encodings 377

Appendix B BNF Grammar		 379

Appendix C Generating and Reading Assembly Listings		 397
Generating Listing Files 397
Precedence of Command-Line Options and Listing Directives 399
Reading the Listing File 399
Generated Code 399
Error Messages 400
Symbols and Abbreviations 400
Reading Tables in a Listing File 404

Appendix D MASM Reserved Words		 407
Operands and Symbols 407
Special Operands for the 80386/486 409
Predefined Symbols 409
Registers 409
Operators and Directives 410
Processor Instructions 412
8086/8088 Processor Instructions 412
80186 Processor Instructions 413
80286 Processor Instructions 413
80286 and 80386 Privileged-Mode Instructions 413
80386 Processor Instructions 413
80486 Processor Instructions 414
Instruction Prefixes 414
Coprocessor Instructions 414
8087 Coprocessor Instructions 414
80287 Privileged-Mode Instruction 415
80387 Instructions 415

Appendix E Default Segment Names		 417

Glossary		 421

Index		 435

Figures and Tables


Figures
1.1 Segment Allocation 6
1.2 Calculating Physical Addresses 8
1.3 Registers for 8088-80286 Processors 17
1.4 Extended Registers for the 80386/486 Processors 18
1.5 Flags for 8088-80486 Processors 20
3.1 Stack Status Before and After Pushes and Pops 72
4.1 Integer Formats 87
4.2 Shifts and Rotates 101
6.1 Encoding for Real Numbers in IEEE Format 138
6.2 Coprocessor Data Registers 140
6.3 Status of the Register Stack 142
6.4 Status of the Register Stack and Memory Locations 143
6.5 Status of the Previously Initialized Register Stack 144
6.6 Status of the Already Initialized Register Stack 144
6.7 Status of the Register Stack: Main Memory and Coprocessor 148
6.8 Coprocessor Control Registers 154
6.9 Coprocessor and Processor Control Flags 155
7.1 Program Arguments on the Stack 183
7.2 Local Variables on the Stack 190
7.3 Operation of Interrupts 206
8.1 Using EXTERNDEF for Variables 215
8.2 Using PROTO and INVOKE 217
8.3 Using PUBLIC and EXTERN 221
11.1 Time Line of Interaction Between Interrupt Handlers for a Typical TSR 278
11.2 Flowchart for SNAP.EXE: Installation Phase 296
11.3 Flowchart for SNAP.EXE Resident Phase 297
11.4 Flowchart for SNAP.EXE Deinstallation Phase 298
12.1 C String Format 316
12.2 C Stack Frame 320
12.3 FORTRAN String Frame 324
12.4 FORTRAN Stack Frame 327
12.5 Basic String Descriptor Format 330
12.6 Basic Stack Frame 333
B.1 BNF Definition of the TYPEDEF Directive 380

Tables
1.1 8086 Family of Processors 2
1.2 The MS-DOS and Windows Operating Systems Compared 4
1.3 Operator Precedence 14
2.1 Attributes of Memory Models 35
3.1 Indirect Addressing with 16-Bit Registers 68
4.1 Division Operations 97
5.1 Requirements for String Instructions 112
6.1 Ranges of Floating-Point Variables 136
6.2 Coprocessor Operand Formats 141
6.3 Control-Flag Settings After Comparison or Test 151
7.1 Conditional Jumps Based on Comparisons of Two Values 167
9.1 MASM Macro Operators 234
11.1 MS-DOS Internal Stacks 286
12.1 Naming and Calling Conventions 309
12.2 Register Conventions for Simple Return Values 317
A.1 Requirements for String Instructions 353
C.1 Options for Generating or Modifying Listing Files 398
C.2 Symbols and Abbreviations in Listings 400
C.3 Symbols in Timing Column 401

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