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The Art of Assembly Language
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The Art of Assembly Language
(Full Contents)
Forward Why Would Anyone Learn This Stuff? .............................................................. 1
1 What's Wrong With Assembly Language ............................................................................ 1
2 What's Right With Assembly Language? ............................................................................. 4
3 Organization of This Text and Pedagogical Concerns ....................................................... 5
4 Obtaining Program Source Listings and Other Materials in This Text ............................... 7
Section One: ................................................................................................................... 9
Machine Organization ........................................................................................................... 9
Chapter One Data Representation ................................................................................ 11
1.0 Chapter Overview ............................................................................................................ 11
1.1 Numbering Systems .......................................................................................................... 11
1.1.1 A Review of the Decimal System ........................................................................... 11
1.1.2 The Binary Numbering System ............................................................................. 12
1.1.3 Binary Formats ....................................................................................................... 13
1.2 Data Organization ............................................................................................................ 13
1.2.1 Bits .......................................................................................................................... 14
1.2.2 Nibbles ................................................................................................................... 14
1.2.3 Bytes ....................................................................................................................... 14
1.2.4 Words ..................................................................................................................... 15
1.2.5 Double Words ........................................................................................................ 16
1.3 The Hexadecimal Numbering System .............................................................................. 17
1.4 Arithmetic Operations on Binary and Hexadecimal Numbers ........................................ 19
1.5 Logical Operations on Bits ............................................................................................... 20
1.6 Logical Operations on Binary Numbers and Bit Strings ................................................. 22
1.7 Signed and Unsigned Numbers ........................................................................................ 23
1.8 Sign and Zero Extension .................................................................................................. 25
1.9 Shifts and Rotates .............................................................................................................. 26
1.10 Bit Fields and Packed Data ............................................................................................. 28
1.11 The ASCII Character Set .................................................................................................. 28
1.12 Summary ......................................................................................................................... 31
1.13 Laboratory Exercises ....................................................................................................... 33
1.13.1 Installing the Software ......................................................................................... 33
1.13.2 Data Conversion Exercises .................................................................................. 34
1.13.3 Logical Operations Exercises ............................................................................... 35
1.13.4 Sign and Zero Extension Exercises ..................................................................... 36
1.13.5 Packed Data Exercises ......................................................................................... 37
1.14 Questions ........................................................................................................................ 38
1.15 Programming Projects .................................................................................................... 41
Chapter Two Boolean Algebra ...................................................................................... 43
2.0 Chapter Overview ............................................................................................................ 43
2.1 Boolean Algebra ............................................................................................................... 43

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2.2 Boolean Functions and Truth Tables ................................................................................45
2.3 Algebraic Manipulation of Boolean Expressions .............................................................48
2.4 Canonical Forms ................................................................................................................49
2.5 Simplification of Boolean Functions .................................................................................52
2.6 What Does This Have To Do With Computers, Anyway? ................................................59
2.6.1 Correspondence Between Electronic Circuits and Boolean Functions ................59
2.6.2 Combinatorial Circuits ............................................................................................60
2.6.3 Sequential and Clocked Logic ................................................................................62
2.7 Okay, What Does It Have To Do With Programming, Then? ..........................................64
2.8 Generic Boolean Functions ..............................................................................................65
2.9 Laboratory Exercises .........................................................................................................69
2.9.1 Truth Tables and Logic Equations Exercises .........................................................70
2.9.2 Canonical Logic Equations Exercises .....................................................................71
2.9.3 Optimization Exercises ...........................................................................................72
2.9.4 Logic Evaluation Exercises .....................................................................................72
2.10 Programming Projects .....................................................................................................77
2.11 Summary ..........................................................................................................................78
2.12 Questions .........................................................................................................................80
Chapter Three System Organization .............................................................................. 83
3.0 Chapter Overview .............................................................................................................83
3.1 The Basic System Components .........................................................................................83
3.1.1 The System Bus ......................................................................................................84
3.1.1.1 The Data Bus ................................................................................................ 84
3.1.1.2 The Address Bus ........................................................................................... 86
3.1.1.3 The Control Bus ............................................................................................ 86
3.1.2 The Memory Subsystem .........................................................................................87
3.1.3 The I/O Subsystem .................................................................................................92
3.2 System Timing ...................................................................................................................92
3.2.1 The System Clock ...................................................................................................92
3.2.2 Memory Access and the System Clock ...................................................................93
3.2.3 Wait States ...............................................................................................................95
3.2.4 Cache Memory ........................................................................................................96
3.3 The 886, 8286, 8486, and 8686 ``Hypothetical'' Processors ..............................................99
3.3.1 CPU Registers ..........................................................................................................99
3.3.2 The Arithmetic & Logical Unit ................................................................................100
3.3.3 The Bus Interface Unit ............................................................................................100
3.3.4 The Control Unit and Instruction Sets ....................................................................100
3.3.5 The x86 Instruction Set ...........................................................................................102
3.3.6 Addressing Modes on the x86 ................................................................................103
3.3.7 Encoding x86 Instructions ......................................................................................104
3.3.8 Step­by­Step Instruction Execution ........................................................................107
3.3.9 The Differences Between the x86 Processors .......................................................109
3.3.10 The 886 Processor ................................................................................................110
3.3.11 The 8286 Processor ...............................................................................................110
3.3.12 The 8486 Processor ...............................................................................................116
3.3.12.1 The 8486 Pipeline ....................................................................................... 117
3.3.12.2 Stalls in a Pipeline ....................................................................................... 118
3.3.12.3 Cache, the Prefetch Queue, and the 8486 .................................................. 119

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3.3.12.4 Hazards on the 8486 .................................................................................. 122
3.3.13 The 8686 Processor .............................................................................................. 123
3.4 I/O (Input/Output) ........................................................................................................... 124
3.5 Interrupts and Polled I/O ................................................................................................. 126
3.6 Laboratory Exercises ......................................................................................................... 128
3.6.1 The SIMx86 Program -- Some Simple x86 Programs ............................................. 128
3.6.2 Simple I/O­Mapped Input/Output Operations ..................................................... 131
3.6.3 Memory Mapped I/O ............................................................................................. 132
3.6.4 DMA Exercises ....................................................................................................... 133
3.6.5 Interrupt Driven I/O Exercises .............................................................................. 134
3.6.6 Machine Language Programming & Instruction Encoding Exercises ................... 135
3.6.7 Self Modifying Code Exercises .............................................................................. 136
3.7 Programming Projects ...................................................................................................... 138
3.8 Summary ........................................................................................................................... 139
3.9 Questions .......................................................................................................................... 142
Chapter Four Memory Layout and Access .................................................................. 145
4.0 Chapter Overview ............................................................................................................ 145
4.1 The 80x86 CPUs:A Programmer's View ........................................................................... 145
4.1.1 8086 General Purpose Registers ............................................................................ 146
4.1.2 8086 Segment Registers ......................................................................................... 147
4.1.3 8086 Special Purpose Registers ............................................................................. 148
4.1.4 80286 Registers ...................................................................................................... 148
4.1.5 80386/80486 Registers ........................................................................................... 149
4.2 80x86 Physical Memory Organization ............................................................................. 150
4.3 Segments on the 80x86 ..................................................................................................... 151
4.4 Normalized Addresses on the 80x86 ................................................................................ 154
4.5 Segment Registers on the 80x86 ....................................................................................... 155
4.6 The 80x86 Addressing Modes .......................................................................................... 155
4.6.1 8086 Register Addressing Modes ........................................................................... 156
4.6.2 8086 Memory Addressing Modes .......................................................................... 156
4.6.2.1 The Displacement Only Addressing Mode ................................................. 156
4.6.2.2 The Register Indirect Addressing Modes ..................................................... 158
4.6.2.3 Indexed Addressing Modes ......................................................................... 159
4.6.2.4 Based Indexed Addressing Modes .............................................................. 160
4.6.2.5 Based Indexed Plus Displacement Addressing Mode ................................ 160
4.6.2.6 An Easy Way to Remember the 8086 Memory Addressing Modes ............. 162
4.6.2.7 Some Final Comments About 8086 Addressing Modes .............................. 162
4.6.3 80386 Register Addressing Modes ......................................................................... 163
4.6.4 80386 Memory Addressing Modes ........................................................................ 163
4.6.4.1 Register Indirect Addressing Modes ............................................................ 163
4.6.4.2 80386 Indexed, Base/Indexed, and Base/Indexed/Disp Addressing Modes 164
4.6.4.3 80386 Scaled Indexed Addressing Modes ................................................... 165
4.6.4.4 Some Final Notes About the 80386 Memory Addressing Modes ................ 165
4.7 The 80x86 MOV Instruction ............................................................................................. 166
4.8 Some Final Comments on the MOV Instructions ............................................................. 169
4.9 Laboratory Exercises ......................................................................................................... 169
4.9.1 The UCR Standard Library for 80x86 Assembly Language Programmers ............. 169
4.9.2 Editing Your Source Files ...................................................................................... 170

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4.9.3 The SHELL.ASM File ...............................................................................................170
4.9.4 Assembling Your Code with MASM .......................................................................172
4.9.5 Debuggers and CodeViewò ..................................................................................173
4.9.5.1 A Quick Look at CodeView .......................................................................... 173
4.9.5.2 The Source Window ..................................................................................... 174
4.9.5.3 The Memory Window ................................................................................... 175
4.9.5.4 The Register Window ................................................................................... 176
4.9.5.5 The Command Window ............................................................................... 176
4.9.5.6 The Output Menu Item ................................................................................. 177
4.9.5.7 The CodeView Command Window ............................................................. 177
4.9.5.7.1 The Radix Command (N) ..................................................................177
4.9.5.7.2 The Assemble Command ..................................................................178
4.9.5.7.3 The Compare Memory Command ....................................................178
4.9.5.7.4 The Dump Memory Command ........................................................180
4.9.5.7.5 The Enter Command .........................................................................181
4.9.5.7.6 The Fill Memory Command ..............................................................182
4.9.5.7.7 The Move Memory Command ..........................................................182
4.9.5.7.8 The Input Command .........................................................................183
4.9.5.7.9 The Output Command ......................................................................183
4.9.5.7.10 The Quit Command ........................................................................183
4.9.5.7.11 The Register Command ..................................................................183
4.9.5.7.12 The Unassemble Command ............................................................184
4.9.5.8 CodeView Function Keys ............................................................................. 184
4.9.5.9 Some Comments on CodeView Addresses .................................................. 185
4.9.5.10 A Wrap on CodeView ................................................................................. 186
4.9.6 Laboratory Tasks ....................................................................................................186
4.10 Programming Projects .....................................................................................................187
4.11 Summary ..........................................................................................................................188
4.12 Questions .........................................................................................................................190
Section Two: ................................................................................................................ 193
Basic Assembly Language ......................................................................................................193
Chapter Five Variables and Data Structures ................................................................ 195
5.0 Chapter Overview .............................................................................................................195
5.1 Some Additional Instructions: LEA, LES, ADD, and MUL .................................................195
5.2 Declaring Variables in an Assembly Language Program ..................................................196
5.3 Declaring and Accessing Scalar Variables ........................................................................197
5.3.1 Declaring and using BYTE Variables .....................................................................198
5.3.2 Declaring and using WORD Variables ...................................................................200
5.3.3 Declaring and using DWORD Variables ................................................................201
5.3.4 Declaring and using FWORD, QWORD, and TBYTE Variables ...........................202
5.3.5 Declaring Floating Point Variables with REAL4, REAL8, and REAL10 ..................202
5.4 Creating Your Own Type Names with TYPEDEF ............................................................203
5.5 Pointer Data Types ............................................................................................................203
5.6 Composite Data Types ......................................................................................................206
5.6.1 Arrays ......................................................................................................................206
5.6.1.1 Declaring Arrays in Your Data Segment ...................................................... 207
5.6.1.2 Accessing Elements of a Single Dimension Array ........................................ 209
5.6.2 Multidimensional Arrays .........................................................................................210
5.6.2.1 Row Major Ordering ..................................................................................... 211

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5.6.2.2 Column Major Ordering ............................................................................... 215
5.6.2.3 Allocating Storage for Multidimensional Arrays .......................................... 216
5.6.2.4 Accessing Multidimensional Array Elements in Assembly Language ......... 217
5.6.3 Structures ............................................................................................................... 218
5.6.4 Arrays of Structures and Arrays/Structures as Structure Fields ............................. 220
5.6.5 Pointers to Structures ............................................................................................. 221
5.7 Sample Programs .............................................................................................................. 222
5.7.1 Simple Variable Declarations ................................................................................ 222
5.7.2 Using Pointer Variables ......................................................................................... 224
5.7.3 Single Dimension Array Access ............................................................................. 226
5.7.4 Multidimensional Array Access ............................................................................. 227
5.7.5 Simple Structure Access ......................................................................................... 229
5.7.6 Arrays of Structures ................................................................................................ 231
5.7.7 Structures and Arrays as Fields of Another Structure ............................................ 233
5.7.8 Pointers to Structures and Arrays of Structures ..................................................... 235
5.8 Laboratory Exercises ......................................................................................................... 237
5.9 Programming Projects ...................................................................................................... 238
5.10 Summary ......................................................................................................................... 239
5.11 Questions ........................................................................................................................ 241
Chapter Six The 80x86 Instruction Set ........................................................................ 243
6.0 Chapter Overview ............................................................................................................ 243
6.1 The Processor Status Register (Flags) ............................................................................... 244
6.2 Instruction Encodings ....................................................................................................... 245
6.3 Data Movement Instructions ............................................................................................ 246
6.3.1 The MOV Instruction ............................................................................................. 246
6.3.2 The XCHG Instruction ........................................................................................... 247
6.3.3 The LDS, LES, LFS, LGS, and LSS Instructions ....................................................... 248
6.3.4 The LEA Instruction ............................................................................................... 248
6.3.5 The PUSH and POP Instructions ........................................................................... 249
6.3.6 The LAHF and SAHF Instructions .......................................................................... 252
6.4 Conversions ...................................................................................................................... 252
6.4.1 The MOVZX, MOVSX, CBW, CWD, CWDE, and CDQ Instructions .................... 252
6.4.2 The BSWAP Instruction ......................................................................................... 254
6.4.3 The XLAT Instruction ............................................................................................. 255
6.5 Arithmetic Instructions ..................................................................................................... 255
6.5.1 The Addition Instructions: ADD, ADC, INC, XADD, AAA, and DAA .................. 256
6.5.1.1 The ADD and ADC Instructions .................................................................. 256
6.5.1.2 The INC Instruction ...................................................................................... 258
6.5.1.3 The XADD Instruction ................................................................................. 258
6.5.1.4 The AAA and DAA Instructions ................................................................... 258
6.5.2 The Subtraction Instructions: SUB, SBB, DEC, AAS, and DAS ............................. 259
6.5.3 The CMP Instruction .............................................................................................. 261
6.5.4 The CMPXCHG, and CMPXCHG8B Instructions .................................................. 263
6.5.5 The NEG Instruction .............................................................................................. 263
6.5.6 The Multiplication Instructions: MUL, IMUL, and AAM ........................................ 264
6.5.7 The Division Instructions: DIV, IDIV, and AAD ................................................... 267
6.6 Logical, Shift, Rotate and Bit Instructions ........................................................................ 269
6.6.1 The Logical Instructions: AND, OR, XOR, and NOT ........................................... 269
6.6.2 The Shift Instructions: SHL/SAL, SHR, SAR, SHLD, and SHRD ............................. 270

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6.6.2.1 SHL/SAL ........................................................................................................ 271
6.6.2.2 SAR ................................................................................................................ 272
6.6.2.3 SHR ................................................................................................................ 273
6.6.2.4 The SHLD and SHRD Instructions ................................................................ 274
6.6.3 The Rotate Instructions: RCL, RCR, ROL, and ROR ................................................276
6.6.3.1 RCL ................................................................................................................ 277
6.6.3.2 RCR ................................................................................................................ 277
6.6.3.3 ROL ............................................................................................................... 278
6.6.3.4 ROR ............................................................................................................... 278
6.6.4 The Bit Operations .................................................................................................279
6.6.4.1 TEST .............................................................................................................. 280
6.6.4.2 The Bit Test Instructions: BT, BTS, BTR, and BTC ...................................... 280
6.6.4.3 Bit Scanning: BSF and BSR ........................................................................... 281
6.6.5 The ``Set on Condition'' Instructions .......................................................................281
6.7 I/O Instructions .................................................................................................................284
6.8 String Instructions ..............................................................................................................284
6.9 Program Flow Control Instructions ...................................................................................286
6.9.1 Unconditional Jumps .............................................................................................286
6.9.2 The CALL and RET Instructions ..............................................................................289
6.9.3 The INT, INTO, BOUND, and IRET Instructions ...................................................292
6.9.4 The Conditional Jump Instructions ........................................................................296
6.9.5 The JCXZ/JECXZ Instructions ................................................................................299
6.9.6 The LOOP Instruction ............................................................................................300
6.9.7 The LOOPE/LOOPZ Instruction ...........................................................................300
6.9.8 The LOOPNE/LOOPNZ Instruction ......................................................................301
6.10 Miscellaneous Instructions .............................................................................................302
6.11 Sample Programs .............................................................................................................303
6.11.1 Simple Arithmetic I ...............................................................................................303
6.11.2 Simple Arithmetic II ..............................................................................................305
6.11.3 Logical Operations ................................................................................................306
6.11.4 Shift and Rotate Operations .................................................................................308
6.11.5 Bit Operations and SETcc Instructions .................................................................310
6.11.6 String Operations ..................................................................................................312
6.11.7 Conditional Jumps ................................................................................................313
6.11.8 CALL and INT Instructions ...................................................................................315
6.11.9 Conditional Jumps I ..............................................................................................317
6.11.10 Conditional Jump Instructions II ........................................................................318
6.12 Laboratory Exercises .......................................................................................................320
6.12.1 The IBM/L System ................................................................................................320
6.12.2 IBM/L Exercises ....................................................................................................327
6.13 Programming Projects .....................................................................................................327
6.14 Summary ..........................................................................................................................328
6.15 Questions .........................................................................................................................331
Chapter Seven The UCR Standard Library ................................................................... 333
7.0 Chapter Overview .............................................................................................................333
7.1 An Introduction to the UCR Standard Library ...................................................................333
7.1.1 Memory Management Routines: MEMINIT, MALLOC, and FREE .........................334
7.1.2 The Standard Input Routines: GETC, GETS, GETSM .............................................334
7.1.3 The Standard Output Routines: PUTC, PUTCR, PUTS, PUTH, PUTI, PRINT, and PRINTF 336

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7.1.4 Formatted Output Routines: Putisize, Putusize, Putlsize, and Putulsize .............. 340
7.1.5 Output Field Size Routines: Isize, Usize, and Lsize .............................................. 340
7.1.6 Conversion Routines: ATOx, and xTOA ............................................................... 341
7.1.7 Routines that Test Characters for Set Membership ............................................... 342
7.1.8 Character Conversion Routines: ToUpper, ToLower ............................................ 343
7.1.9 Random Number Generation: Random, Randomize ............................................ 343
7.1.10 Constants, Macros, and other Miscellany ............................................................ 344
7.1.11 Plus more! ............................................................................................................ 344
7.2 Sample Programs .............................................................................................................. 344
7.2.1 Stripped SHELL.ASM File ....................................................................................... 345
7.2.2 Numeric I/O ........................................................................................................... 345
7.3 Laboratory Exercises ......................................................................................................... 348
7.3.1 Obtaining the UCR Standard Library ..................................................................... 348
7.3.2 Unpacking the Standard Library ............................................................................ 349
7.3.3 Using the Standard Library .................................................................................... 349
7.3.4 The Standard Library Documentation Files ........................................................... 350
7.4 Programming Projects ...................................................................................................... 351
7.5 Summary ........................................................................................................................... 351
7.6 Questions .......................................................................................................................... 353
Chapter Eight MASM: Directives & Pseudo­Opcodes ................................................ 355
8.0 Chapter Overview ............................................................................................................ 355
8.1 Assembly Language Statements ....................................................................................... 355
8.2 The Location Counter ...................................................................................................... 357
8.3 Symbols ............................................................................................................................. 358
8.4 Literal Constants .............................................................................................................. 359
8.4.1 Integer Constants ................................................................................................... 360
8.4.2 String Constants ..................................................................................................... 361
8.4.3 Real Constants ........................................................................................................ 361
8.4.4 Text Constants ....................................................................................................... 362
8.5 Declaring Manifest Constants Using Equates ................................................................... 362
8.6 Processor Directives ......................................................................................................... 364
8.7 Procedures ........................................................................................................................ 365
8.8 Segments ........................................................................................................................... 366
8.8.1 Segment Names ..................................................................................................... 367
8.8.2 Segment Loading Order ......................................................................................... 368
8.8.3 Segment Operands ................................................................................................ 369
8.8.3.1 The ALIGN Type .......................................................................................... 369
8.8.3.2 The COMBINE Type .................................................................................... 373
8.8.4 The CLASS Type ..................................................................................................... 374
8.8.5 The Read­only Operand ........................................................................................ 375
8.8.6 The USE16, USE32, and FLAT Options ................................................................. 375
8.8.7 Typical Segment Definitions ................................................................................. 376
8.8.8 Why You Would Want to Control the Loading Order .......................................... 376
8.8.9 Segment Prefixes ................................................................................................... 377
8.8.10 Controlling Segments with the ASSUME Directive ............................................. 377
8.8.11 Combining Segments: The GROUP Directive ..................................................... 380
8.8.12 Why Even Bother With Segments? ...................................................................... 383
8.9 The END Directive ............................................................................................................ 384

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8.10 Variables ..........................................................................................................................384
8.11 Label Types ......................................................................................................................385
8.11.1 How to Give a Symbol a Particular Type .............................................................385
8.11.2 Label Values ..........................................................................................................386
8.11.3 Type Conflicts .......................................................................................................386
8.12 Address Expressions ........................................................................................................387
8.12.1 Symbol Types and Addressing Modes .................................................................387
8.12.2 Arithmetic and Logical Operators ........................................................................388
8.12.3 Coercion ................................................................................................................390
8.12.4 Type Operators ....................................................................................................392
8.12.5 Operator Precedence ............................................................................................396
8.13 Conditional Assembly .....................................................................................................397
8.13.1 IF Directive ...........................................................................................................398
8.13.2 IFE directive ..........................................................................................................399
8.13.3 IFDEF and IFNDEF ...............................................................................................399
8.13.4 IFB, IFNB ..............................................................................................................399
8.13.5 IFIDN, IFDIF, IFIDNI, and IFDIFI ........................................................................400
8.14 Macros ..............................................................................................................................400
8.14.1 Procedural Macros ................................................................................................400
8.14.2 Macros vs. 80x86 Procedures ...............................................................................404
8.14.3 The LOCAL Directive ............................................................................................406
8.14.4 The EXITM Directive ............................................................................................406
8.14.5 Macro Parameter Expansion and Macro Operators .............................................407
8.14.6 A Sample Macro to Implement For Loops ...........................................................409
8.14.7 Macro Functions ...................................................................................................413
8.14.8 Predefined Macros, Macro Functions, and Symbols ............................................414
8.14.9 Macros vs. Text Equates .......................................................................................418
8.14.10 Macros: Good and Bad News .............................................................................419
8.15 Repeat Operations ...........................................................................................................420
8.16 The FOR and FORC Macro Operations ..........................................................................421
8.17 The WHILE Macro Operation .........................................................................................422
8.18 Macro Parameters ............................................................................................................422
8.19 Controlling the Listing .....................................................................................................424
8.19.1 The ECHO and %OUT Directives ........................................................................424
8.19.2 The TITLE Directive ..............................................................................................424
8.19.3 The SUBTTL Directive ..........................................................................................424
8.19.4 The PAGE Directive ..............................................................................................424
8.19.5 The .LIST, .NOLIST, and .XLIST Directives ..........................................................425
8.19.6 Other Listing Directives ........................................................................................425
8.20 Managing Large Programs ...............................................................................................425
8.20.1 The INCLUDE Directive .......................................................................................426
8.20.2 The PUBLIC, EXTERN, and EXTRN Directives ....................................................427
8.20.3 The EXTERNDEF Directive ..................................................................................428
8.21 Make Files ........................................................................................................................429
8.22 Sample Program ..............................................................................................................432
8.22.1 EX8.MAK ...............................................................................................................432
8.22.2 Matrix.A .................................................................................................................432
8.22.3 EX8.ASM ...............................................................................................................433
8.22.4 GETI.ASM ..............................................................................................................442

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8.22.5 GetArray.ASM ....................................................................................................... 443
8.22.6 XProduct.ASM ...................................................................................................... 445
8.23 Laboratory Exercises ....................................................................................................... 447
8.23.1 Near vs. Far Procedures ....................................................................................... 447
8.23.2 Data Alignment Exercises .................................................................................... 448
8.23.3 Equate Exercise .................................................................................................... 449
8.23.4 IFDEF Exercise ..................................................................................................... 450
8.23.5 Make File Exercise ............................................................................................... 451
8.24 Programming Projects .................................................................................................... 453
8.25 Summary ......................................................................................................................... 453
8.26 Questions ........................................................................................................................ 456
Chapter Nine Arithmetic and Logical Operations ...................................................... 459
9.0 Chapter Overview ............................................................................................................ 459
9.1 Arithmetic Expressions ..................................................................................................... 460
9.1.1 Simple Assignments ............................................................................................... 460
9.1.2 Simple Expressions ................................................................................................ 460
9.1.3 Complex Expressions ............................................................................................ 462
9.1.4 Commutative Operators ........................................................................................ 466
9.2 Logical (Boolean) Expressions ......................................................................................... 467
9.3 Multiprecision Operations ................................................................................................ 470
9.3.1 Multiprecision Addition Operations ...................................................................... 470
9.3.2 Multiprecision Subtraction Operations ................................................................. 472
9.3.3 Extended Precision Comparisons .......................................................................... 473
9.3.4 Extended Precision Multiplication ........................................................................ 475
9.3.5 Extended Precision Division ................................................................................. 477
9.3.6 Extended Precision NEG Operations .................................................................... 480
9.3.7 Extended Precision AND Operations .................................................................... 481
9.3.8 Extended Precision OR Operations ....................................................................... 482
9.3.9 Extended Precision XOR Operations .................................................................... 482
9.3.10 Extended Precision NOT Operations .................................................................. 482
9.3.11 Extended Precision Shift Operations ................................................................... 482
9.3.12 Extended Precision Rotate Operations ................................................................ 484
9.4 Operating on Different Sized Operands .......................................................................... 485
9.5 Machine and Arithmetic Idioms ....................................................................................... 486
9.5.1 Multiplying Without MUL and IMUL ..................................................................... 487
9.5.2 Division Without DIV and IDIV ............................................................................ 488
9.5.3 Using AND to Compute Remainders ..................................................................... 488
9.5.4 Implementing Modulo­n Counters with AND ....................................................... 489
9.5.5 Testing an Extended Precision Value for 0FFFF..FFh ........................................... 489
9.5.6 TEST Operations ................................................................................................... 489
9.5.7 Testing Signs with the XOR Instruction ................................................................ 490
9.6 Masking Operations ......................................................................................................... 490
9.6.1 Masking Operations with the AND Instruction ..................................................... 490
9.6.2 Masking Operations with the OR Instruction ....................................................... 491
9.7 Packing and Unpacking Data Types ................................................................................ 491
9.8 Tables ................................................................................................................................ 493
9.8.1 Function Computation via Table Look Up ............................................................ 493
9.8.2 Domain Conditioning ............................................................................................ 496

Page xii
9.8.3 Generating Tables ..................................................................................................497
9.9 Sample Programs ...............................................................................................................498
9.9.1 Converting Arithmetic Expressions to Assembly Language ..................................498
9.9.2 Boolean Operations Example ................................................................................500
9.9.3 64­bit Integer I/O ....................................................................................................503
9.9.4 Packing and Unpacking Date Data Types .............................................................506
9.10 Laboratory Exercises .......................................................................................................509
9.10.1 Debugging Programs with CodeView .................................................................509
9.10.2 Debugging Strategies ............................................................................................511
9.10.2.1 Locating Infinite Loops ............................................................................... 511
9.10.2.2 Incorrect Computations .............................................................................. 512
9.10.2.3 Illegal Instructions/Infinite Loops Part II ................................................... 513
9.10.3 Debug Exercise I: Using CodeView to Find Bugs in a Calculation .....................513
9.10.4 Software Delay Loop Exercises ............................................................................515
9.11 Programming Projects .....................................................................................................516
9.12 Summary ..........................................................................................................................516
9.13 Questions .........................................................................................................................518
Chapter 10 Control Structures ...................................................................................... 521
10.0 Chapter Overview ...........................................................................................................521
10.1 Introduction to Decisions ................................................................................................521
10.2 IF..THEN..ELSE Sequences ..............................................................................................522
10.3 CASE Statements ..............................................................................................................525
10.4 State Machines and Indirect Jumps .................................................................................529
10.5 Spaghetti Code ................................................................................................................531
10.6 Loops ...............................................................................................................................531
10.6.1 While Loops ..........................................................................................................532
10.6.2 Repeat..Until Loops ..............................................................................................532
10.6.3 LOOP..ENDLOOP Loops ......................................................................................533
10.6.4 FOR Loops ............................................................................................................533
10.7 Register Usage and Loops ...............................................................................................534
10.8 Performance Improvements ............................................................................................535
10.8.1 Moving the Termination Condition to the End of a Loop ...................................535
10.8.2 Executing the Loop Backwards ............................................................................537
10.8.3 Loop Invariant Computations ...............................................................................538
10.8.4 Unraveling Loops .................................................................................................539
10.8.5 Induction Variables ..............................................................................................540
10.8.6 Other Performance Improvements ......................................................................541
10.9 Nested Statements ...........................................................................................................542
10.10 Timing Delay Loops ......................................................................................................544
10.11 Sample Program ............................................................................................................547
10.12 Laboratory Exercises .....................................................................................................552
10.12.1 The Physics of Sound .........................................................................................552
10.12.2 The Fundamentals of Music ...............................................................................553
10.12.3 The Physics of Music ..........................................................................................554
10.12.4 The 8253/8254 Timer Chip .................................................................................555
10.12.5 Programming the Timer Chip to Produce Musical Tones .................................555
10.12.6 Putting it All Together .........................................................................................556

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10.12.7 Amazing Grace Exercise .................................................................................... 557
10.13 Programming Projects ................................................................................................... 558
10.14 Summary ....................................................................................................................... 559
10.15 Questions ...................................................................................................................... 561
Chapter 11 Procedures and Functions ........................................................................ 565
11.0 Chapter Overview ........................................................................................................... 565
11.1 Procedures ...................................................................................................................... 566
11.2 Near and Far Procedures ................................................................................................ 568
11.2.1 Forcing NEAR or FAR CALLs and Returns ........................................................... 568
11.2.2 Nested Procedures ............................................................................................... 569
11.3 Functions ........................................................................................................................ 572
11.4 Saving the State of the Machine ..................................................................................... 572
11.5 Parameters ...................................................................................................................... 574
11.5.1 Pass by Value ....................................................................................................... 574
11.5.2 Pass by Reference ................................................................................................ 575
11.5.3 Pass by Value­Returned ....................................................................................... 575
11.5.4 Pass by Result ....................................................................................................... 576
11.5.5 Pass by Name ....................................................................................................... 576
11.5.6 Pass by Lazy­Evaluation ....................................................................................... 577
11.5.7 Passing Parameters in Registers ........................................................................... 578
11.5.8 Passing Parameters in Global Variables .............................................................. 580
11.5.9 Passing Parameters on the Stack ......................................................................... 581
11.5.10 Passing Parameters in the Code Stream ............................................................ 590
11.5.11 Passing Parameters via a Parameter Block ........................................................ 598
11.6 Function Results .............................................................................................................. 600
11.6.1 Returning Function Results in a Register ............................................................. 601
11.6.2 Returning Function Results on the Stack ............................................................. 601
11.6.3 Returning Function Results in Memory Locations .............................................. 602
11.7 Side Effects ...................................................................................................................... 602
11.8 Local Variable Storage .................................................................................................... 604
11.9 Recursion ........................................................................................................................ 606
11.10 Sample Program ............................................................................................................ 610
11.11 Laboratory Exercises ..................................................................................................... 618
11.11.1 Ex11_1.cpp ......................................................................................................... 619
11.11.2 Ex11_1.asm ........................................................................................................ 621
11.11.3 EX11_1a.asm ...................................................................................................... 625
11.12 Programming Projects ................................................................................................... 632
11.13 Summary ....................................................................................................................... 633
11.14 Questions ...................................................................................................................... 635
Section Three: ............................................................................................................. 637
Intermediate Level Assembly Language Programming ........................................................ 637
Chapter 12 Procedures: Advanced Topics .................................................................. 639
12.0 Chapter Overview ........................................................................................................... 639
12.1 Lexical Nesting, Static Links, and Displays .................................................................... 639
12.1.1 Scope .................................................................................................................... 640

Page xiv
12.1.2 Unit Activation, Address Binding, and Variable Lifetime ....................................642
12.1.3 Static Links ............................................................................................................642
12.1.4 Accessing Non­Local Variables Using Static Links ...............................................647
12.1.5 The Display ...........................................................................................................648
12.1.6 The 80286 ENTER and LEAVE Instructions ..........................................................650
12.2 Passing Variables at Different Lex Levels as Parameters. ...............................................652
12.2.1 Passing Parameters by Value in a Block Structured Language ............................652
12.2.2 Passing Parameters by Reference, Result, and Value­Result in a Block Structured Language 653
12.2.3 Passing Parameters by Name and Lazy­Evaluation in a Block Structured Language 654
12.3 Passing Parameters as Parameters to Another Procedure ..............................................655
12.3.1 Passing Reference Parameters to Other Procedures ............................................656
12.3.2 Passing Value­Result and Result Parameters as Parameters ................................657
12.3.3 Passing Name Parameters to Other Procedures ..................................................657
12.3.4 Passing Lazy Evaluation Parameters as Parameters .............................................658
12.3.5 Parameter Passing Summary ................................................................................658
12.4 Passing Procedures as Parameters ..................................................................................659
12.5 Iterators ............................................................................................................................663
12.5.1 Implementing Iterators Using In­Line Expansion ................................................664
12.5.2 Implementing Iterators with Resume Frames ......................................................666
12.6 Sample Programs .............................................................................................................669
12.6.1 An Example of an Iterator ....................................................................................669
12.6.2 Another Iterator Example .....................................................................................673
12.7 Laboratory Exercises .......................................................................................................678
12.7.1 Iterator Exercise ....................................................................................................678
12.7.2 The 80x86 Enter and Leave Instructions ..............................................................684
12.7.3 Parameter Passing Exercises ................................................................................690
12.8 Programming Projects .....................................................................................................695
12.9 Summary ..........................................................................................................................697
12.10 Questions .......................................................................................................................698
Chapter 13 MS­DOS, PC­BIOS, and File I/O ............................................................... 699
13.0 Chapter Overview ...........................................................................................................700
13.1 The IBM PC BIOS ............................................................................................................701
13.2 An Introduction to the BIOS' Services ............................................................................701
13.2.1 INT 5­ Print Screen ...............................................................................................702
13.2.2 INT 10h ­ Video Services ......................................................................................702
13.2.3 INT 11h ­ Equipment Installed .............................................................................704
13.2.4 INT 12h ­ Memory Available ................................................................................704
13.2.5 INT 13h ­ Low Level Disk Services .......................................................................704
13.2.6 INT 14h ­ Serial I/O ..............................................................................................706
13.2.6.1 AH=0: Serial Port Initialization ................................................................... 706
13.2.6.2 AH=1: Transmit a Character to the Serial Port ........................................... 707
13.2.6.3 AH=2: Receive a Character from the Serial Port ........................................ 707
13.2.6.4 AH=3: Serial Port Status ............................................................................. 707
13.2.7 INT 15h ­ Miscellaneous Services .........................................................................708
13.2.8 INT 16h ­ Keyboard Services ................................................................................708
13.2.8.1 AH=0: Read a Key From the Keyboard ...................................................... 709
13.2.8.2 AH=1: See if a Key is Available at the Keyboard ...................................... 709
13.2.8.3 AH=2: Return Keyboard Shift Key Status ................................................... 710
13.2.9 INT 17h ­ Printer Services .....................................................................................710

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13.2.9.1 AH=0: Print a Character ............................................................................. 711
13.2.9.2 AH=1: Initialize Printer ............................................................................... 711
13.2.9.3 AH=2: Return Printer Status ....................................................................... 711
13.2.10 INT 18h ­ Run BASIC ......................................................................................... 712
13.2.11 INT 19h ­ Reboot Computer .............................................................................. 712
13.2.12 INT 1Ah ­ Real Time Clock ................................................................................ 712
13.2.12.1 AH=0: Read the Real Time Clock ............................................................. 712
13.2.12.2 AH=1: Setting the Real Time Clock .......................................................... 713
13.3 An Introduction to MS­DOSò ........................................................................................ 713
13.3.1 MS­DOS Calling Sequence ................................................................................... 714
13.3.2 MS­DOS Character Oriented Functions ............................................................... 714
13.3.3 MS­DOS Drive Commands .................................................................................. 716
13.3.4 MS­DOS ``Obsolete'' Filing Calls .......................................................................... 717
13.3.5 MS­DOS Date and Time Functions ...................................................................... 718
13.3.6 MS­DOS Memory Management Functions .......................................................... 718
13.3.6.1 Allocate Memory ........................................................................................ 719
13.3.6.2 Deallocate Memory .................................................................................... 719
13.3.6.3 Modify Memory Allocation ........................................................................ 719
13.3.6.4 Advanced Memory Management Functions .............................................. 720
13.3.7 MS­DOS Process Control Functions .................................................................... 721
13.3.7.1 Terminate Program Execution ................................................................... 721
13.3.7.2 Terminate, but Stay Resident ..................................................................... 721
13.3.7.3 Execute a Program ..................................................................................... 722
13.3.8 MS­DOS ``New'' Filing Calls ................................................................................. 725
13.3.8.1 Open File .................................................................................................... 725
13.3.8.2 Create File .................................................................................................. 726
13.3.8.3 Close File .................................................................................................... 727
13.3.8.4 Read From a File ........................................................................................ 727
13.3.8.5 Write to a File ............................................................................................. 728
13.3.8.6 Seek (Move File Pointer) ............................................................................ 728
13.3.8.7 Set Disk Transfer Address (DTA) ............................................................... 729
13.3.8.8 Find First File .............................................................................................. 729
13.3.8.9 Find Next File ............................................................................................. 730
13.3.8.10 Delete File ................................................................................................ 730
13.3.8.11 Rename File .............................................................................................. 730
13.3.8.12 Change/Get File Attributes ..................................................................... 731
13.3.8.13 Get/Set File Date and Time ...................................................................... 731
13.3.8.14 Other DOS Calls ....................................................................................... 732
13.3.9 File I/O Examples ................................................................................................ 734
13.3.9.1 Example #1: A Hex Dump Utility .............................................................. 734
13.3.9.2 Example #2: Upper Case Conversion ........................................................ 735
13.3.10 Blocked File I/O ................................................................................................ 737
13.3.11 The Program Segment Prefix (PSP) ................................................................... 739
13.3.12 Accessing Command Line Parameters ............................................................... 742
13.3.13 ARGC and ARGV ................................................................................................ 750
13.4 UCR Standard Library File I/O Routines ........................................................................ 751
13.4.1 Fopen ................................................................................................................... 751
13.4.2 Fcreate .................................................................................................................. 752
13.4.3 Fclose ................................................................................................................... 752
13.4.4 Fflush .................................................................................................................... 752
13.4.5 Fgetc ..................................................................................................................... 752
13.4.6 Fread .................................................................................................................... 753
13.4.7 Fputc .................................................................................................................... 753

Page xvi
13.4.8 Fwrite ....................................................................................................................753
13.4.9 Redirecting I/O Through the StdLib File I/O Routines ........................................753
13.4.10 A File I/O Example .............................................................................................755
13.5 Sample Program ..............................................................................................................758
13.6 Laboratory Exercises .......................................................................................................763
13.7 Programming Projects .....................................................................................................768
13.8 Summary ..........................................................................................................................768
13.9 Questions .........................................................................................................................770
Chapter 14 Floating Point Arithmetic .......................................................................... 771
14.0 Chapter Overview ...........................................................................................................771
14.1 The Mathematics of Floating Point Arithmetic ...............................................................771
14.2 IEEE Floating Point Formats ............................................................................................774
14.3 The UCR Standard Library Floating Point Routines ........................................................777
14.3.1 Load and Store Routines .......................................................................................778
14.3.2 Integer/Floating Point Conversion .......................................................................779
14.3.3 Floating Point Arithmetic ......................................................................................780
14.3.4 Float/Text Conversion and Printff ........................................................................780
14.4 The 80x87 Floating Point Coprocessors .........................................................................781
14.4.1 FPU Registers ........................................................................................................781
14.4.1.1 The FPU Data Registers .............................................................................. 782
14.4.1.2 The FPU Control Register ........................................................................... 782
14.4.1.3 The FPU Status Register .............................................................................. 785
14.4.2 FPU Data Types ....................................................................................................788
14.4.3 The FPU Instruction Set ........................................................................................789
14.4.4 FPU Data Movement Instructions ........................................................................789
14.4.4.1 The FLD Instruction .................................................................................... 789
14.4.4.2 The FST and FSTP Instructions ................................................................... 790
14.4.4.3 The FXCH Instruction ................................................................................. 790
14.4.5 Conversions ..........................................................................................................791
14.4.5.1 The FILD Instruction ................................................................................... 791
14.4.5.2 The FIST and FISTP Instructions ................................................................ 791
14.4.5.3 The FBLD and FBSTP Instructions ............................................................. 792
14.4.6 Arithmetic Instructions .........................................................................................792
14.4.6.1 The FADD and FADDP Instructions .......................................................... 792
14.4.6.2 The FSUB, FSUBP, FSUBR, and FSUBRP Instructions ............................... 793
14.4.6.3 The FMUL and FMULP Instructions ............................................................ 794
14.4.6.4 The FDIV, FDIVP, FDIVR, and FDIVRP Instructions ................................. 794
14.4.6.5 The FSQRT Instruction ............................................................................... 795
14.4.6.6 The FSCALE Instruction .............................................................................. 795
14.4.6.7 The FPREM and FPREM1 Instructions ........................................................ 795
14.4.6.8 The FRNDINT Instruction ........................................................................... 796
14.4.6.9 The FXTRACT Instruction ........................................................................... 796
14.4.6.10 The FABS Instruction ................................................................................ 796
14.4.6.11 The FCHS Instruction ................................................................................ 797
14.4.7 Comparison Instructions ......................................................................................797
14.4.7.1 The FCOM, FCOMP, and FCOMPP Instructions ........................................ 797
14.4.7.2 The FUCOM, FUCOMP, and FUCOMPP Instructions ................................ 798
14.4.7.3 The FTST Instruction .................................................................................. 798
14.4.7.4 The FXAM Instruction ................................................................................. 798
14.4.8 Constant Instructions ............................................................................................798

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Page xvii
14.4.9 Transcendental Instructions ................................................................................ 799
14.4.9.1 The F2XM1 Instruction ............................................................................... 799
14.4.9.2 The FSIN, FCOS, and FSINCOS Instructions ............................................. 799
14.4.9.3 The FPTAN Instruction .............................................................................. 799
14.4.9.4 The FPATAN Instruction ............................................................................ 800
14.4.9.5 The FYL2X and FYL2XP1 Instructions ....................................................... 800
14.4.10 Miscellaneous instructions ................................................................................. 800
14.4.10.1 The FINIT and FNINIT Instructions ......................................................... 800
14.4.10.2 The FWAIT Instruction ............................................................................. 801
14.4.10.3 The FLDCW and FSTCW Instructions ...................................................... 801
14.4.10.4 The FCLEX and FNCLEX Instructions ...................................................... 801
14.4.10.5 The FLDENV, FSTENV, and FNSTENV Instructions ................................ 801
14.4.10.6 The FSAVE, FNSAVE, and FRSTOR Instructions ..................................... 802
14.4.10.7 The FSTSW and FNSTSW Instructions ..................................................... 803
14.4.10.8 The FINCSTP and FDECSTP Instructions ................................................ 803
14.4.10.9 The FNOP Instruction .............................................................................. 803
14.4.10.10 The FFREE Instruction ............................................................................ 803
14.4.11 Integer Operations ............................................................................................. 803
14.5 Sample Program: Additional Trigonometric Functions ................................................. 804
14.6 Laboratory Exercises ....................................................................................................... 810
14.6.1 FPU vs StdLib Accuracy ....................................................................................... 811
14.7 Programming Projects .................................................................................................... 814
14.8 Summary ......................................................................................................................... 814
14.9 Questions ........................................................................................................................ 817
Chapter 15 Strings and Character Sets ......................................................................... 819
15.0 Chapter Overview ........................................................................................................... 819
15.1 The 80x86 String Instructions ......................................................................................... 819
15.1.1 How the String Instructions Operate ................................................................... 819
15.1.2 The REP/REPE/REPZ and REPNZ/REPNE Prefixes ............................................. 820
15.1.3 The Direction Flag ............................................................................................... 821
15.1.4 The MOVS Instruction ......................................................................................... 822
15.1.5 The CMPS Instruction .......................................................................................... 826
15.1.6 The SCAS Instruction ........................................................................................... 828
15.1.7 The STOS Instruction ........................................................................................... 828
15.1.8 The LODS Instruction .......................................................................................... 829
15.1.9 Building Complex String Functions from LODS and STOS ................................ 830
15.1.10 Prefixes and the String Instructions ................................................................... 830
15.2 Character Strings ............................................................................................................. 831
15.2.1 Types of Strings .................................................................................................... 831
15.2.2 String Assignment ................................................................................................ 832
15.2.3 String Comparison ............................................................................................... 834
15.3 Character String Functions ............................................................................................. 835
15.3.1 Substr .................................................................................................................... 835
15.3.2 Index ................................................................................................................... 838
15.3.3 Repeat ................................................................................................................. 840
15.3.4 Insert ................................................................................................................... 841
15.3.5 Delete ................................................................................................................... 843
15.3.6 Concatenation ...................................................................................................... 844
15.4 String Functions in the UCR Standard Library ................................................................ 845

Page xviii
15.4.1 StrBDel, StrBDelm ................................................................................................846
15.4.2 Strcat, Strcatl, Strcatm, Strcatml ............................................................................847
15.4.3 Strchr .....................................................................................................................848
15.4.4 Strcmp, Strcmpl, Stricmp, Stricmpl .......................................................................848
15.4.5 Strcpy, Strcpyl, Strdup, Strdupl .............................................................................849
15.4.6 Strdel, Strdelm .......................................................................................................850
15.4.7 Strins, Strinsl, Strinsm, Strinsml ............................................................................851
15.4.8 Strlen .....................................................................................................................852
15.4.9 Strlwr, Strlwrm, Strupr, Struprm ...........................................................................852
15.4.10 Strrev, Strrevm .....................................................................................................853
15.4.11 Strset, Strsetm ......................................................................................................853
15.4.12 Strspan, Strspanl, Strcspan, Strcspanl .................................................................854
15.4.13 Strstr, Strstrl .........................................................................................................855
15.4.14 Strtrim, Strtrimm ..................................................................................................855
15.4.15 Other String Routines in the UCR Standard Library ...........................................856
15.5 The Character Set Routines in the UCR Standard Library ...............................................856
15.6 Using the String Instructions on Other Data Types ........................................................859
15.6.1 Multi­precision Integer Strings .............................................................................859
15.6.2 Dealing with Whole Arrays and Records .............................................................860
15.7 Sample Programs .............................................................................................................860
15.7.1 Find.asm ................................................................................................................860
15.7.2 StrDemo.asm .........................................................................................................862
15.7.3 Fcmp.asm ..............................................................................................................865
15.8 Laboratory Exercises .......................................................................................................868
15.8.1 MOVS Performance Exercise #1 ...........................................................................868
15.8.2 MOVS Performance Exercise #2 ...........................................................................870
15.8.3 Memory Performance Exercise ............................................................................872
15.8.4 The Performance of Length­Prefixed vs. Zero­Terminated Strings .....................874
15.9 Programming Projects .....................................................................................................878
15.10 Summary ........................................................................................................................878
15.11 Questions .......................................................................................................................881
Chapter 16 Pattern Matching ....................................................................................... 883
16.1 An Introduction to Formal Language (Automata) Theory .............................................883
16.1.1 Machines vs. Languages .......................................................................................883
16.1.2 Regular Languages ................................................................................................884
16.1.2.1 Regular Expressions .................................................................................... 885
16.1.2.2 Nondeterministic Finite State Automata (NFAs) ........................................ 887
16.1.2.3 Converting Regular Expressions to NFAs ................................................... 888
16.1.2.4 Converting an NFA to Assembly Language ................................................ 890
16.1.2.5 Deterministic Finite State Automata (DFAs) .............................................. 893
16.1.2.6 Converting a DFA to Assembly Language .................................................. 895
16.1.3 Context Free Languages .......................................................................................900
16.1.4 Eliminating Left Recursion and Left Factoring CFGs ...........................................903
16.1.5 Converting REs to CFGs .......................................................................................905
16.1.6 Converting CFGs to Assembly Language .............................................................905
16.1.7 Some Final Comments on CFGs ...........................................................................912
16.1.8 Beyond Context Free Languages .........................................................................912
16.2 The UCR Standard Library Pattern Matching Routines ...................................................913
16.3 The Standard Library Pattern Matching Functions .........................................................914

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Page xix
16.3.1 Spancset ............................................................................................................... 914
16.3.2 Brkcset .................................................................................................................. 915
16.3.3 Anycset ................................................................................................................. 915
16.3.4 Notanycset ........................................................................................................... 916
16.3.5 MatchStr ................................................................................................................ 916
16.3.6 MatchiStr ............................................................................................................... 916
16.3.7 MatchToStr ........................................................................................................... 917
16.3.8 MatchChar ............................................................................................................ 917
16.3.9 MatchToChar ........................................................................................................ 918
16.3.10 MatchChars ......................................................................................................... 918
16.3.11 MatchToPat ........................................................................................................ 918
16.3.12 EOS ..................................................................................................................... 919
16.3.13 ARB ..................................................................................................................... 919
16.3.14 ARBNUM ............................................................................................................ 920
16.3.15 Skip ..................................................................................................................... 920
16.3.16 Pos ...................................................................................................................... 921
16.3.17 RPos .................................................................................................................... 921
16.3.18 GotoPos .............................................................................................................. 921
16.3.19 RGotoPos ........................................................................................................... 922
16.3.20 SL_Match2 .......................................................................................................... 922
16.4 Designing Your Own Pattern Matching Routines .......................................................... 922
16.5 Extracting Substrings from Matched Patterns ................................................................ 925
16.6 Semantic Rules and Actions ............................................................................................ 929
16.7 Constructing Patterns for the MATCH Routine .............................................................. 933
16.8 Some Sample Pattern Matching Applications ................................................................ 935
16.8.1 Converting Written Numbers to Integers ............................................................ 935
16.8.2 Processing Dates .................................................................................................. 941
16.8.3 Evaluating Arithmetic Expressions ...................................................................... 948
16.8.4 A Tiny Assembler ................................................................................................. 953
16.8.5 The ``MADVENTURE'' Game ................................................................................ 963
16.9 Laboratory Exercises ....................................................................................................... 979
16.9.1 Checking for Stack Overflow (Infinite Loops) .................................................... 979
16.9.2 Printing Diagnostic Messages from a Pattern ...................................................... 984
16.10 Programming Projects ................................................................................................... 988
16.11 Summary ....................................................................................................................... 988
16.12 Questions ...................................................................................................................... 991
Section Four: ............................................................................................................... 993
Advanced Assembly Language Programming ...................................................................... 993
Chapter 17 Interrupts, Traps, and Exceptions ............................................................ 995
17.1 80x86 Interrupt Structure and Interrupt Service Routines (ISRs) .................................. 996
17.2 Traps ............................................................................................................................... 999
17.3 Exceptions ...................................................................................................................... 1000
17.3.1 Divide Error Exception (INT 0) ........................................................................... 1000
17.3.2 Single Step (Trace) Exception (INT 1) ................................................................ 1000
17.3.3 Breakpoint Exception (INT 3) ............................................................................. 1001
17.3.4 Overflow Exception (INT 4/INTO) ..................................................................... 1001
17.3.5 Bounds Exception (INT 5/BOUND) ................................................................... 1001
17.3.6 Invalid Opcode Exception (INT 6) ...................................................................... 1004

Page xx
17.3.7 Coprocessor Not Available (INT 7) ......................................................................1004
17.4 Hardware Interrupts ........................................................................................................1004
17.4.1 The 8259A Programmable Interrupt Controller (PIC) .........................................1005
17.4.2 The Timer Interrupt (INT 8) .................................................................................1007
17.4.3 The Keyboard Interrupt (INT 9) ...........................................................................1008
17.4.4 The Serial Port Interrupts (INT 0Bh and INT 0Ch) ..............................................1008
17.4.5 The Parallel Port Interrupts (INT 0Dh and INT 0Fh) ...........................................1008
17.4.6 The Diskette and Hard Drive Interrupts (INT 0Eh and INT 76h) ........................1009
17.4.7 The Real­Time Clock Interrupt (INT 70h) ............................................................1009
17.4.8 The FPU Interrupt (INT 75h) ................................................................................1009
17.4.9 Nonmaskable Interrupts (INT 2) ..........................................................................1009
17.4.10 Other Interrupts ..................................................................................................1009
17.5 Chaining Interrupt Service Routines ...............................................................................1010
17.6 Reentrancy Problems ......................................................................................................1012
17.7 The Efficiency of an Interrupt Driven System ................................................................1014
17.7.1 Interrupt Driven I/O vs. Polling ...........................................................................1014
17.7.2 Interrupt Service Time ..........................................................................................1015
17.7.3 Interrupt Latency ..................................................................................................1016
17.7.4 Prioritized Interrupts .............................................................................................1020
17.8 Debugging ISRs ...............................................................................................................1020
17.9 Summary ..........................................................................................................................1021
Chapter 18 Resident Programs ................................................................................... 1025
18.1 DOS Memory Usage and TSRs ........................................................................................1025
18.2 Active vs. Passive TSRs ....................................................................................................1029
18.3 Reentrancy .......................................................................................................................1032
18.3.1 Reentrancy Problems with DOS ...........................................................................1032
18.3.2 Reentrancy Problems with BIOS ..........................................................................1033
18.3.3 Reentrancy Problems with Other Code ...............................................................1034
18.4 The Multiplex Interrupt (INT 2Fh) ..................................................................................1034
18.5 Installing a TSR ................................................................................................................1035
18.6 Removing a TSR ...............................................................................................................1037
18.7 Other DOS Related Issues ...............................................................................................1039
18.8 A Keyboard Monitor TSR ................................................................................................1041
18.9 Semiresident Programs ....................................................................................................1055
18.10 Summary ........................................................................................................................1064
Chapter 19 Processes, Coroutines, and Concurrency ............................................... 1065
19.1 DOS Processes .................................................................................................................1065
19.1.1 Child Processes in DOS ........................................................................................1065
19.1.1.1 Load and Execute ....................................................................................... 1066
19.1.1.2 Load Program .............................................................................................. 1068
19.1.1.3 Loading Overlays ........................................................................................ 1069
19.1.1.4 Terminating a Process ................................................................................. 1069
19.1.1.5 Obtaining the Child Process Return Code ................................................. 1070
19.1.2 Exception Handling in DOS: The Break Handler ................................................1070
19.1.3 Exception Handling in DOS: The Critical Error Handler .....................................1071
19.1.4 Exception Handling in DOS: Traps ......................................................................1075
19.1.5 Redirection of I/O for Child Processes ................................................................1075

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19.2 Shared Memory ............................................................................................................... 1078
19.2.1 Static Shared Memory .......................................................................................... 1078
19.2.2 Dynamic Shared Memory .................................................................................... 1088
19.3 Coroutines ....................................................................................................................... 1103
19.4 Multitasking .................................................................................................................... 1124
19.4.1 Lightweight and HeavyWeight Processes ........................................................... 1124
19.4.2 The UCR Standard Library Processes Package .................................................... 1125
19.4.3 Problems with Multitasking ................................................................................. 1126
19.4.4 A Sample Program with Threads ......................................................................... 1127
19.5 Synchronization .............................................................................................................. 1129
19.5.1 Atomic Operations, Test & Set, and Busy­Waiting ............................................. 1132
19.5.2 Semaphores .......................................................................................................... 1134
19.5.3 The UCR Standard Library Semaphore Support .................................................. 1136
19.5.4 Using Semaphores to Protect Critical Regions .................................................... 1136
19.5.5 Using Semaphores for Barrier Synchronization .................................................. 1140
19.6 Deadlock ......................................................................................................................... 1146
19.7 Summary ......................................................................................................................... 1147
Section Five: .............................................................................................................. 1151
The PC's I/O Ports ................................................................................................................. 1151
Chapter 20 The PC Keyboard .................................................................................... 1153
20.1 Keyboard Basics ............................................................................................................. 1153
20.2 The Keyboard Hardware Interface ................................................................................ 1159
20.3 The Keyboard DOS Interface ......................................................................................... 1167
20.4 The Keyboard BIOS Interface ........................................................................................ 1168
20.5 The Keyboard Interrupt Service Routine ....................................................................... 1174
20.6 Patching into the INT 9 Interrupt Service Routine ......................................................... 1184
20.7 Simulating Keystrokes .................................................................................................... 1186
20.7.1 Stuffing Characters in the Type Ahead Buffer ..................................................... 1186
20.7.2 Using the 80x86 Trace Flag to Simulate IN AL, 60H Instructions ....................... 1187
20.7.3 Using the 8042 Microcontroller to Simulate Keystrokes ..................................... 1192
20.8 Summary ......................................................................................................................... 1196
Chapter 21 The PC Parallel Ports .............................................................................. 1199
21.1 Basic Parallel Port Information ....................................................................................... 1199
21.2 The Parallel Port Hardware ............................................................................................ 1201
21.3 Controlling a Printer Through the Parallel Port ............................................................. 1202
21.3.1 Printing via DOS .................................................................................................. 1203
21.3.2 Printing via BIOS ................................................................................................. 1203
21.3.3 An INT 17h Interrupt Service Routine ................................................................. 1203
21.4 Inter­Computer Communications on the Parallel Port .................................................. 1209
21.5 Summary ......................................................................................................................... 1222
Chapter 22 The PC Serial Ports .................................................................................. 1223
22.1 The 8250 Serial Communications Chip .......................................................................... 1223
22.1.1 The Data Register (Transmit/Receive Register) .................................................. 1224
22.1.2 The Interrupt Enable Register (IER) .................................................................... 1224
22.1.3 The Baud Rate Divisor ......................................................................................... 1225

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22.1.4 The Interrupt Identification Register (IIR) ...........................................................1226
22.1.5 The Line Control Register .....................................................................................1227
22.1.6 The Modem Control Register ...............................................................................1228
22.1.7 The Line Status Register (LSR) ..............................................................................1229
22.1.8 The Modem Status Register (MSR) .......................................................................1230
22.1.9 The Auxiliary Input Register .................................................................................1231
22.2 The UCR Standard Library Serial Communications Support Routines ...........................1231
22.3 Programming the 8250 (Examples from the Standard Library) ......................................1233
22.4 Summary ..........................................................................................................................1244
Chapter 23 The PC Video Display ............................................................................. 1247
23.1 Memory Mapped Video ..................................................................................................1247
23.2 The Video Attribute Byte .................................................................................................1248
23.3 Programming the Text Display .......................................................................................1249
23.4 Summary ..........................................................................................................................1252
Chapter 24 The PC Game Adapter ............................................................................ 1255
24.1 Typical Game Devices .....................................................................................................1255
24.2 The Game Adapter Hardware .........................................................................................1257
24.3 Using BIOS' Game I/O Functions ...................................................................................1259
24.4 Writing Your Own Game I/O Routines ..........................................................................1260
24.5 The Standard Game Device Interface (SGDI) ................................................................1262
24.5.1 Application Programmer's Interface (API) ...........................................................1262
24.5.2 Read4Sw ...............................................................................................................1263
24.5.3 Read4Pots: ............................................................................................................1263
24.5.4 ReadPot .................................................................................................................1264
24.5.5 Read4: ...................................................................................................................1264
24.5.6 CalibratePot ..........................................................................................................1264
24.5.7 TestPotCalibration ................................................................................................1264
24.5.8 ReadRaw ...............................................................................................................1265
24.5.9 ReadSwitch ...........................................................................................................1265
24.5.10 Read16Sw ............................................................................................................1265
24.5.11 Remove ...............................................................................................................1265
24.5.12 TestPresence .......................................................................................................1265
24.5.13 An SGDI Driver for the Standard Game Adapter Card ......................................1265
24.6 An SGDI Driver for the CH Products' Flight Stick Proò ................................................1280
24.7 Patching Existing Games .................................................................................................1293
24.8 Summary ..........................................................................................................................1306
Section Six: ................................................................................................................ 1309
Optimization ...........................................................................................................................1309
Chapter 25 Optimizing Your Programs ..................................................................... 1311
25.0 Chapter Overview ...........................................................................................................1311
25.1 When to Optimize, When Not to Optimize ....................................................................1311
25.2 How Do You Find the Slow Code in Your Programs? ...................................................1313
25.3 Is Optimization Necessary? .............................................................................................1314
25.4 The Three Types of Optimization ...................................................................................1315
25.5 Improving the Implementation of an Algorithm ............................................................1317

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25.6 Summary ......................................................................................................................... 1341
Section Seven: ........................................................................................................... 1343
Appendixes ............................................................................................................................ 1343
Appendix A: ASCII/IBM Character Set ...................................................................... 1345
Appendix B: Annotated Bibliography ....................................................................... 1347
Appendix C: Keyboard Scan Codes .......................................................................... 1351
Appendix D: Instruction Set Reference ..................................................................... 1361

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