Programming in C

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18 Debugging Programs THIS CHAPTER TEACHES YOU TWO TECHNIQUES you can use to debug your programs. One involves using the preprocessor to allow for the conditional inclusion of debugging statements in your program.The other technique involves the use of an interactive debugger. In this chapter, you are introduced to a popular debugger called gdb.Even if you use a different debugger (such as dbx, or one built in to an IDE tool), it is likely that your debugger will have similarities to gdb. Debugging with the Preprocessor As noted in Chapter 13,“The Preprocessor,” conditional compilation is useful when debugging programs.The C preprocessor can be used to insert debugging code into your program. By appropriate use of #ifdef statements, the debugging code can be enabled or disabled at your discretion. Program 18.1 is a program (admittedly contrived) that reads in three integers and prints out their sum. Note that when the preprocessor identifier DEBUG is defined, the debugging code (which prints to stderr) is compiled with the rest of the program, and when DEBUG isn’t defined, the debugging code is left out. Program 18.1 Adding Debug Statements with the Preprocessor #include #define DEBUG int process (int i, int j, int k) { return i + j + k; }
390 Chapter 18 Debugging Programs Program 18.1 Continued int main (void) { int i, j, k, nread; nread = scanf ("%d %d %d", &i, &j, &k); #ifdef DEBUG fprintf (stderr, "Number of integers read = %i\n", nread); fprintf (stderr, "i = %i, j = %i, k = %i\n", i, j, k); #endif } printf ("%i\n", process (i, j, k)); return 0; Program 18.1 Output 1 2 3 Number of integers read = 3 i = 1, j = 2, k = 3 6 Program 18.1 Output (Rerun) 1 2 e Number of integers read = 2 i = 1, j = 2, k = 0 3 Note that the value displayed for k can be anything because its value was not set by the scanf call and it was not initialized by the program. The statements #ifdef DEBUG fprintf (stderr, "Number of integers read = %i\n", nread); fprintf (stderr, "i = %d, j = %d, k = %d\n", i, j, k); #endif are analyzed by the preprocessor. If the identifier DEBUG has been previously defined (#ifdef DEBUG), the preprocessor sends the statements that follow up to the #endif (the two fprintfs) to the compiler to be compiled. If DEBUG hasn’t been defined, the two
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Programming in C Third Edition
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Programming in C Third Edition Step
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❖ To my mother and father ❖
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Table of Contents 1 Introduction 1
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Contents ix Character Arrays 108 Ba
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Contents xi Pointers to Functions 2
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Contents xiii 17 Miscellaneous and
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Contents xv 6.0 Storage Classes and
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Preface It’s hard to believe that
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Acknowledgements I wish to thank th
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1 Introduction THE C PROGRAMMING LA
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Introduction 3 terminology. It also
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6 Chapter 2 Some Fundamentals Highe
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8 Chapter 2 Some Fundamentals durin
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10 Chapter 2 Some Fundamentals the
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12 Chapter 3 Compiling and Running
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22 Chapter 4 Variables, Data Types,
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5 Program Looping IFYOU ARRANGE 15
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The for Statement 45 Program 5.2 Co
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The for Statement 47 When the loop_
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The for Statement 49 constitutes th
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The for Statement 51 The primary ch
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The for Statement 53 Nested for Loo
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The for Statement 55 Multiple Expre
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The while Statement 57 Program 5.6
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The while Statement 59 Program 5.7
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The do Statement 61 do program stat
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Exercises 63 Now that you are famil
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6 Making Decisions IN CHAPTER 5,“
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The if Statement 67 The program was
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The if Statement 69 would do the tr
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The if Statement 71 When writing pr
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The if Statement 73 To illustrate t
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The if Statement 75 Nested if State
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The if Statement 77 separate if sta
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The if Statement 79 Program 6.7 Con
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The if Statement 81 Program 6.8 Con
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The if Statement 83 Program 6.8A Co
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The switch Statement 85 if ( expres
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Boolean Variables 87 switch (operat
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Boolean Variables 89 “off,” its
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The Conditional Operator 91 Program
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Exercises 93 Exercises 1. Type in a
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7 Working with Arrays THE C LANGUAG
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Defining an Array 97 sequences thro
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Defining an Array 99 values [0] 197
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Defining an Array 101 proceeding wi
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Defining an Array 103 As a point of
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Defining an Array 105 the term “p
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Initializing Arrays 107 Arrays of c
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Character Arrays 109 The most notab
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Character Arrays 111 Program 7.7 Co
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Multidimensional Arrays 113 example
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Variable-Length Arrays 115 Pay part
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Exercises 117 than 1 or greater tha
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8 Working with Functions BEHIND ALL
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Defining a Function 121 appears.Thi
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Arguments and Local Variables 123 p
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Arguments and Local Variables 125 w
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Returning Function Results 127 defi
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Returning Function Results 129 In C
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Functions Calling Functions Calling
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Functions and Arrays 137 As you can
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Functions and Arrays 139 Program 8.
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Functions and Arrays 143 When you w
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Functions and Arrays 147 An entire
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Global Variables 153 In Program 8.1
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Global Variables 155 much improved
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Automatic and Static Variables 157
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Recursive Functions 159 Recursive F
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Recursive Functions 161 With the va
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Exercises 163 represents a quadrati
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9 Working with Structures CHAPTER 7
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A Structure for Storing the Date 16
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A Structure for Storing the Date 16
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Functions and Structures 171 end of
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Functions and Structures 173 Progra
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Functions and Structures 177 illust
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Initializing Structures 181 sets th
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Arrays of Structures 183 Initializa
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Structures Containing Structures 18
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Structures Containing Arrays 187 Na
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Structures Containing Arrays 189 Pr
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Exercises 191 struct date { int mon
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Exercises 193 previously.This funct
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196 Chapter 10 Character Strings Ar
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198 Chapter 10 Character Strings Th
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200 Chapter 10 Character Strings Pr
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202 Chapter 10 Character Strings ca
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204 Chapter 10 Character Strings Te
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208 Chapter 10 Character Strings In
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214 Chapter 10 Character Strings of
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216 Chapter 10 Character Strings Es
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218 Chapter 10 Character Strings co
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220 Chapter 10 Character Strings In
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224 Chapter 10 Character Strings No
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228 Chapter 10 Character Strings ca
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232 Chapter 10 Character Strings to
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11 Pointers IN THIS CHAPTER,YOU EXA
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Defining a Pointer Variable 237 Pro
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Using Pointers in Expressions 239 (
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Working with Pointers and Structure
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The Keyword const and Pointers 253
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Pointers and Functions 255 Program
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Pointers and Functions 257 You shou
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Pointers and Arrays 259 displayed.T
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Pointers and Arrays 261 To set text
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Pointers and Arrays 263 Program 11.
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Pointers and Arrays 265 eliminate t
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Pointers and Arrays 267 Program 11.
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Pointers and Arrays 269 just seen,
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Pointers and Arrays 271 Execution o
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Pointers to Functions 273 Program 1
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Pointers and Memory Addresses 275 m
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Exercises 277 8. Write a function c
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280 Chapter 12 Operations on Bits T
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282 Chapter 12 Operations on Bits W
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284 Chapter 12 Operations on Bits B
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286 Chapter 12 Operations on Bits w
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288 Chapter 12 Operations on Bits h
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290 Chapter 12 Operations on Bits I
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292 Chapter 12 Operations on Bits P
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294 Chapter 12 Operations on Bits o
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296 Chapter 12 Operations on Bits }
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298 Chapter 12 Operations on Bits a
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300 Chapter 13 The Preprocessor def
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302 Chapter 13 The Preprocessor By
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304 Chapter 13 The Preprocessor the
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306 Chapter 13 The Preprocessor els
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308 Chapter 13 The Preprocessor are
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310 Chapter 13 The Preprocessor ass
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312 Chapter 13 The Preprocessor The
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314 Chapter 13 The Preprocessor Sup
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316 Chapter 13 The Preprocessor Sys
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318 Chapter 13 The Preprocessor wan
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320 Chapter 13 The Preprocessor Exe
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322 Chapter 14 More on Data Types d
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324 Chapter 14 More on Data Types P
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326 Chapter 14 More on Data Types T
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328 Chapter 14 More on Data Types 4
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330 Chapter 14 More on Data Types F
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15 Working with Larger Programs THE
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Dividing Your Program into Multiple
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Communication Between Modules 337 v
Page 360 and 361: Communication Between Modules 339 S
Page 362 and 363: Communication Between Modules 341 U
Page 364 and 365: Other Utilities for Working with La
Page 366: Other Utilities for Working with La
Page 369 and 370: 348 Chapter 16 Input and Output Ope
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Page 413 and 414: 392 Chapter 18 Debugging Programs P
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Page 432 and 433: 19 Object-Oriented Programming BECA
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Page 436 and 437: Defining an Objective-C Class to Wo
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Page 446 and 447: A C Language Summary THIS SECTION S
Page 448 and 449: 3.0 Constants 427 3.0 Constants 3.1
Page 450 and 451: 3.0 Constants 429 In the octal char
Page 452 and 453: 4.0 Data Types and Declarations 431
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5.0 Expressions 439 As an example,
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5.0 Expressions 441 Table A.5 Conti
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5.0 Expressions 443 1. As the value
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5.0 Expressions 445 The usual arith
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5.0 Expressions 447 5.11 sizeof Ope
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5.0 Expressions 449 Pointers to Arr
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5.0 Expressions 451 Types other tha
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6.0 Storage Classes and Scope 453 T
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7.0 Functions 455 int printf (char
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8.0 Statements 457 Execution of a b
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8.0 Statements 459 the null stateme
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9.0 The Preprocessor 461 Table A.7
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9.0 The Preprocessor 463 produces p
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9.0 The Preprocessor 465 In either
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B The Standard C Library THE STANDA
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Standard Header Files 469 This hea
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String Functions 471 char *strerror
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I/O Functions 473 Character Functio
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I/O Functions 475 FILE *fopen (file
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I/O Functions 477 size_t fwrite (bu
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String-to-Number Conversion 479 int
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Dynamic Memory Allocation Functions
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Math Functions 483 int islessequal
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Math Functions 485 double fma (x, y
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Math Functions 487 double remquo (x
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Math Functions 489 double complex c
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General Utility Functions 491 argum
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494 Appendix C Compiling Programs w
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D Common Programming Mistakes THE F
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Common Programming Mistakes 499 7.
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E Resources THIS APPENDIX CONTAINS
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Miscellaneous 503 Visual Studio htt
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Index Symbols \’ (single quote) e
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arrays 507 functions, 122-123 decla
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C language 509 bits, 279 bit fields
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character strings 511 calculating a
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copying 513 Compiling the Debug Cod
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derived data types 515 breakpoint d
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file I/O operations 517 enumerated
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functions 519 formatted I/O operati
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functions 521 I/O, 473-478 fclose(
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grep utility 523 strncat( ), 471 st
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int data type 525 programs Calculat
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macros 527 llround( ) function, 486
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OOP 529 multiple source files, comp
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prime numbers 531 character string
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programs 533 bitwise operators, Ill
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eferencing defined values 535 synta
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statements 537 search methods binar
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summing array elements 539 string_l
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variable-length character strings 5
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Xcode 543 Introducing the while Sta
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