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How to learn C Programming

how to learn basic c programming language and how to learn c coding language | Let Us C | pdf free download
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Let Us C Fifth Edition Yashavant P. Kanetkar Dedicated to baba Who couldn’t be here to see this day... About the Author Destiny drew Yashavant Kanetkar towards computers when the IT industry was just making a beginning in India. Having completed his education from VJTI Mumbai and IIT Kanpur in Mechanical Engineering he started his training company in Nagpur. Yashavant has a passion for writing and is an author of several books in C, C++, VC++, C, .NET, DirectX and COM programming. He is a much sought after speaker on various technology subjects and is a regular columnist for Express Computers and Developer 2.0. His current affiliations include being a Director of KICIT, a training company and DCube Software Technologies, a software development company. In recognition to his contribution Microsoft awarded him the prestigious “Best .NET Technical Contributor” award recently. He can be reached at kanetkarkicit.com. Preface to the Fifth Edition It is mid 2004. World has left behind the DOTCOM bust, 9/11 tragedy, the economic downturn, etc. and moved on. Countless Indians have relentlessly worked for close to two decades to successfully establish “India” as a software brand. At times I take secret pleasure in seeing that a book that I have been part of, has contributed in its own little way in shaping so many budding careers that have made the “India” brand acceptable. Computing and the way people use C for doing it keeps changing as years go by. So overwhelming has been the response to all the previous editions of “Let Us C” that I have now decided that each year I would come up with a new edition of it so that I can keep the readers abreast with the way C is being used at that point in time. There are two phases in every C programmer’s life. In the first phase he is a learner trying to understand the language elements and their nuances. At this stage he wants a simple learning environment that helps him to master the language. In my opinion, even today there isn’t any learning environment that can beat Turbo C/C++ for simplicity. Hence the first fifteen chapters are written keeping this environment in mind, though a majority of these programs in these chapters would work with any C compiler. Armed with the knowledge of language elements the C programmer enters the second phase. Here he wishes to use all that he has learnt to create programs that match the ability of programs that he see in today’s world. I am pointing towards programs in Windows and Linux world. Chapters 16 to 21 are devoted to this. I would like to your attention the fact that if you want to program Windows or Linux you need to have a very good grasp over the programming model used by each of these OS. Windows messaging architecture and Linux signaling mechanism are the cases in point. Once you understand these thoroughly rest is just a vimatter of time. Chapters 16 to 21 have been written with this motive. In Linux programming the basic hurdle is in choosing the Linux distribution, compiler, editor, shell, libraries, etc. To get a head- start you can follow the choices that I found most reasonable and simple. They have been mentioned in Chapter 20 and Appendix H. Once you are comfortable you can explore other choices. In fourth edition of Let Us C there were chapters on ‘Disk Basics’, ‘VDU Basics’, ‘Graphics’, ‘Mouse Programming’, ‘C and Assembly’. Though I used to like these chapters a lot I had to take a decision to drop them since most of them were DOS-centric and would not be so useful in modern-day programming. Modern counterparts of all of these have been covered in Chapters 16 to 21. However, if you still need the chapters from previous edition they are available at www.kicit.com/books/letusc/fourthedition. Also, all the programs present in the book are available in source code form at www.kicit.com/books/letusc/sourcecode. You are free to download them, improve them, change them, do whatever with them. If you wish to get solutions for the Exercises in the book they are available in another book titled ‘Let Us C Solutions’. ‘Let Us C’ is as much your book as it is mine. So if you feel that I could have done certain job better than what I have, or you have any suggestions about what you would like to see in the next edition, please drop a line to letuscsuggestionskicit.com. All the best and happy programming viiContents 1. Getting Started 1 What is C 2 Getting Started with C 4 The C Character Set 5 Constants, Variables and Keywords 6 Types of C Constants 7 Rules for Constructing Integer Constants 8 Rules for Constructing Real Constants 9 Rules for Constructing Character Constants 10 Types of C Variables 11 Rules for Constructing Variable Names 11 C Keywords 12 The First C Program 13 Compilation and Execution 19 Receiving Input 21 C Instructions 23 Type Declaration Instruction 24 Arithmetic Instruction 25 Integer and Float Conversions 29 Type Conversion in Assignments 29 Hierarchy of Operations 31 Associativity of Operators 34 Control Instructions in C 37 Summary 37 Exercise 38 2. The Decision Control Structure 49 Decisions Decisions 50 The if Statement 51 The Real Thing 55 Multiple Statements within if 56 The if-else Statement 58 viiiNested if-elses 61 Forms of if 62 Use of Logical Operators 64 The else if Clause 66 The Operator 72 Hierarchy of Operators Revisited 73 A Word of Caution 73 The Conditional Operators 76 Summary 77 Exercise 78 3. The Loop Control Structure 97 Loops 98 The while Loop 99 Tips and Traps 101 More Operators 105 The for Loop 107 Nesting of Loops 114 Multiple Initialisations in the for Loop 115 The Odd Loop 116 The break Statement 118 The continue Statement 120 The do-while Loop 121 Summary 124 Exercise 124 4. The Case Control Structure 135 Decisions Using switch 136 The Tips and Traps 140 switch Versus if-else Ladder 144 The goto Keyword 145 Summary 148 Exercise 149 ix5. Functions & Pointers 157 What is a Function 158 Why Use Functions 165 Passing Values between Functions 166 Scope Rule of Functions 171 Calling Convention 172 One Dicey Issue 173 Advanced Features of Functions 174 Function Declaration and Prototypes 175 Call by Value and Call by Reference 178 An Introduction to Pointers 178 Pointer Notation 179 Back to Function Calls 186 Conclusions 189 Recursion 189 Recursion and Stack 194 Adding Functions to the Library 197 Summary 201 Exercise 201 6. Data Types Revisited 213 Integers, long and short 214 Integers, signed and unsigned 216 Chars, signed and unsigned 217 Floats and Doubles 219 A Few More Issues… 221 Storage Classes in C 223 Automatic Storage Class 224 Register Storage Class 226 Static Storage Class 227 External Storage Class 230 Which to Use When 233 Summary 234 Exercise 235 x 7. The C Preprocessor 241 Features of C Preprocessor 242 Macro Expansion 244 Macros with Arguments 248 Macros versus Functions 252 File Inclusion 253 Conditional Compilation 255 if and elif Directives 258 Miscellaneous Directives 260 undef Directive 260 pragma Directive 261 Summary 263 Exercise 264 8. Arrays 269 What are Arrays 270 A Simple Program Using Array 272 More on Arrays 275 Array Initialization 275 Bounds Checking 276 Passing Array Elements to a Function 277 Pointers and Arrays 279 Passing an Entire Array to a Function 286 The Real Thing 287 Two Dimensional Arrays 289 Initializing a 2-Dimensional Array 290 Memory Map of a 2-Dimensional Array 291 Pointers and 2-Dimensional Arrays 292 Pointer to an Array 295 Passing 2-D array to a Function 297 Array of Pointers 300 Three Dimensional Array 302 Summary 304 xiExercise 304 9. Puppetting On Strings 327 What are Strings 328 More about Strings 329 Pointers and Strings 334 Standard Library String Functions 335 strlen( ) 337 strcpy( ) 339 strcat( ) 342 strcmp( ) 343 Two-Dimensional Array of Characters 344 Array of Pointers to Strings 347 Limitation of Array of Pointers to Strings 351 Solution 352 Summary 353 Exercise 354 10. Structures 363 Why Use Structures 364 Declaring a Structure 367 Accessing Structure Elements 370 How Structure Elements are Stored 370 Array of Structures 371 Additional Features of Structures 374 Uses of Structures 383 Summary 384 Exercise 384 11. Console Input/Output 393 Types of I/O 394 Console I/O Functions 395 Formatted Console I/O Functions 396 xiisprintf( ) and sscanf( ) Functions 404 Unformatted Console I/O Functions 405 Summary 409 Exercise 409 12. File Input/Output 415 Data Organization 416 File Operations 417 Opening a File 418 Reading from a File 420 Trouble in Opening a File 421 Closing the File 422 Counting Characters, Tabs, Spaces, … 422 A File-copy Program 424 Writing to a File 425 File Opening Modes 426 String (line) I/O in Files 427 The Awkward Newline 430 Record I/O in Files 430 Text Files and Binary Files 434 Record I/O Revisited 437 Database Management 441 Low Level Disk I/O 447 A Low Level File-copy Program 448 I/O Under Windows 453 Summary 453 Exercise 454 13. More Issues In Input/Output 465 Using argc and argv 466 Detecting Errors in Reading/Writing 470 Standard I/O Devices 472 I/O Redirection 473 Redirecting the Output 474 xiiiRedirecting the Input 476 Both Ways at Once 477 Summary 478 Exercise 478 14. Operations On Bits 481 Bitwise Operators 482 One’s Complement Operator 484 Right Shift Operator 486 Left Shift Operator 488 Bitwise AND Operator 493 Bitwise OR Operator 498 Bitwise XOR Operator 499 The showbits( ) Function 500 Summary 501 Exercise 501 15. Miscellaneous Features 505 Enumerated Data Type 506 Uses of Enumerated Data Type 507 Renaming Data Types with typedef 510 Typecasting 511 Bit Fields 513 Pointers to Functions 515 Functions Returning Pointers 518 Functions with Variable Number of Arguments 520 Unions 524 Union of Structures 530 Summary 531 Exercise 531 xiv 16. C Under Windows 535 Which Windows… 536 Integers 537 The Use of typedef 537 Pointers in the 32-bit World 539 Memory Management 540 Device Access 543 DOS Programming Model 543 Windows Programming Model 547 Event Driven Model 551 Windows Programming, a Closer Look 552 The First Windows Program 554 Hungarian Notation 558 Summary 558 Exercise 559 17. Windows Programming 561 The Role of a Message Box 562 Here Comes the window… 563 More Windows 566 A Real-World Window 567 Creation and Displaying of Window 569 Interaction with Window 570 Reacting to Messages 572 Program Instances 575 Summary 575 Exercise 576 18. Graphics Under Windows 579 Graphics as of Now 580 Device Independent Drawing 580 xvHello Windows 582 Drawing Shapes 586 Types of Pens 590 Types of Brushes 592 Code and Resources 596 Freehand Drawing, the Paintbrush Style 596 Capturing the Mouse 600 Device Context, a Closer Look 601 Displaying a Bitmap 603 Animation at Work 607 WM_CREATE and OnCreate( ) 611 WM_TIMER and OnTimer( ) 611 A Few More Points… 612 Windows, the Endless World… 613 Summary 614 Exercise 615 19. Interaction With Hardware 617 Hardware Interaction 618 Hardware Interaction, DOS Perspective 619 Hardware Interaction, Windows Perspective 623 Communication with Storage Devices 626 The ReadSector( ) Function 631 Accessing Other Storage Devices 633 Communication with Keyboard 634 Dynamic Linking 635 Windows Hooks 635 Caps Locked, Permanently 637 Did You Press It TTwwiiccee…… 643 Mangling Keys 644 KeyLogger 645 Where is This Leading 646 Summary 647 Exercise 647 xvi20. C Under Linux 649 What is Linux 650 C Programming Under Linux 651 The ‘Hello Linux’ Program 652 Processes 653 Parent and Child Processes 655 More Processes 659 Zombies and Orphans 660 One Interesting Fact 663 Summary 664 Exercise 664 21. More Linux Programming 667 Communication using Signals 668 Handling Multiple Signals 671 Registering a Common Handler 673 Blocking Signals 675 Event Driven Programming 678 Where Do You Go From Here 684 Summary 684 Exercise 685 Appendix A – Precedence Table 687 Appendix B – Standard Library Functions 691 Appendix C – Chasing the Bugs 701 Appendix D – Hexadecimal Numbering 713 Appendix E – ASCII Chart 719 Appendix F – Helper.h File 725 Appendix G – Boot Parameters 729 Appendix H – Linux Installation 735 Index 739 xvii1 Getting Started • What is C • Getting Started with C The C Character Set Constants, Variables and Keywords Types of C Constants Rules for Constructing Integer Constants Rules for Constructing Real Constants Rules for Constructing Character Constants Types of C Variables Rules for Constructing Variable Names C Keywords • The First C Program • Compilation and Execution • Receiving Input • C Instructions Type Declaration Instruction Arithmetic Instruction Integer and Float Conversions Hierarchy of Operations Associativity Of Operators • Control Instruction in C • Summary • Exercise 1 2 Let Us C efore we can begin to write serious programs in C, it would be interesting to find out what really is C, how it came into B existence and how does it compare with other computer languages. In this chapter we would briefly outline these issues. Four important aspects of any language are the way it stores data, the way it operates upon this data, how it accomplishes input and output and how it lets you control the sequence of execution of instructions in a program. We would discuss the first three of these building blocks in this chapter. What is C C is a programming language developed at AT & T’s Bell Laboratories of USA in 1972. It was designed and written by a man named Dennis Ritchie. In the late seventies C began to replace the more familiar languages of that time like PL/I, ALGOL, etc. No one pushed C. It wasn’t made the ‘official’ Bell Labs language. Thus, without any advertisement C’s reputation spread and its pool of users grew. Ritchie seems to have been rather surprised that so many programmers preferred C to older languages like FORTRAN or PL/I, or the newer ones like Pascal and APL. But, that's what happened. Possibly why C seems so popular is because it is reliable, simple and easy to use. Moreover, in an industry where newer languages, tools and technologies emerge and vanish day in and day out, a language that has survived for more than 3 decades has to be really good. An opinion that is often heard today is – “C has been already superceded by languages like C++, C and Java, so why bother to Chapter 1: Getting Started 3 learn C today”. I seriously beg to differ with this opinion. There are several reasons for this: (a) I believe that nobody can learn C++ or Java directly. This is because while learning these languages you have things like classes, objects, inheritance, polymorphism, templates, exception handling, references, etc. do deal with apart from knowing the actual language elements. Learning these complicated concepts when you are not even comfortable with the basic language elements is like putting the cart before the horse. Hence one should first learn all the language elements very thoroughly using C language before migrating to C++, C or Java. Though this two step learning process may take more time, but at the end of it you will definitely find it worth the trouble. (b) C++, C or Java make use of a principle called Object Oriented Programming (OOP) to organize the program. This organizing principle has lots of advantages to offer. But even while using this organizing principle you would still need a good hold over the language elements of C and the basic programming skills. (c) Though many C++ and Java based programming tools and frameworks have evolved over the years the importance of C is still unchallenged because knowingly or unknowingly while using these frameworks and tools you would be still required to use the core C language elements—another good reason why one should learn C before C++, C or Java. (d) Major parts of popular operating systems like Windows, UNIX, Linux is still written in C. This is because even today when it comes to performance (speed of execution) nothing beats C. Moreover, if one is to extend the operating system to work with new devices one needs to write device driver programs. These programs are exclusively written in C. 4 Let Us C (e) Mobile devices like cellular phones and palmtops are becoming increasingly popular. Also, common consumer devices like microwave oven, washing machines and digital cameras are getting smarter by the day. This smartness comes from a microprocessor, an operating system and a program embedded in this devices. These programs not only have to run fast but also have to work in limited amount of memory. No wonder that such programs are written in C. With these constraints on time and space, C is the language of choice while building such operating systems and programs. (f) You must have seen several professional 3D computer games where the user navigates some object, like say a spaceship and fires bullets at the invaders. The essence of all such games is speed. Needless to say, such games won't become popular if they takes a long time to move the spaceship or to fire a bullet. To match the expectations of the player the game has to react fast to the user inputs. This is where C language scores over other languages. Many popular gaming frameworks have been built using C language. (g) At times one is required to very closely interact with the hardware devices. Since C provides several language elements that make this interaction feasible without compromising the performance it is the preferred choice of the programmer. I hope that these are very convincing reasons why one should adopt C as the first and the very important step in your quest for learning programming languages. Getting Started with C Communicating with a computer involves speaking the language the computer understands, which immediately rules out English as the language of communication with computer. However, there is Chapter 1: Getting Started 5 a close analogy between learning English language and learning C language. The classical method of learning English is to first learn the alphabets used in the language, then learn to combine these alphabets to form words, which in turn are combined to form sentences and sentences are combined to form paragraphs. Learning C is similar and easier. Instead of straight-away learning how to write programs, we must first know what alphabets, numbers and special symbols are used in C, then how using them constants, variables and keywords are constructed, and finally how are these combined to form an instruction. A group of instructions would be combined later on to form a program. This is illustrated in the Figure 1.1. Steps in learning English language: Alphabets Words Sentences Paragraphs Steps in learning C: Alphabets Constants Digits Variables Special sy- Instructions Program Keywords mbols Figure 1.1 The C Character Set A character denotes any alphabet, digit or special symbol used to represent information. Figure 1.2 shows the valid alphabets, numbers and special symbols allowed in C.