Let Us C: Authentic Guide to C PROGRAMMING Language (17th Edition)

357 Pages·17·5.42 MB·

by  Yashavant Kanetkar

Let Us C
Seventeenth Edition
Yashavant Kanetkar
SEVENTEENTH REVISED AND UPDATED EDITION 2020
FIRST EDITION 2007
Reprinted 2019
Copyright © BPB Publications, India
© Let Us C is a registered trademark of BPB Publications, New Delhi, under Registration No: 1135514
ISBN: 978-93-89845-686
All Rights Reserved. No part of this publication may be reproduced or distributed in any form or by any means or stored in a database or retrieval
system, without the prior written permission of the publisher.
LIMITS OF LIABILITY AND DISCLAIMER OF WARRANTY
The Author and Publisher of this book have tried their best to ensure that the programmes, procedures and functions described in the book arc
correct. However, the author and the publishers make no warranty, of any kind, expressed or implied, with regard to these programmes or the
documentation contained in the book. The author and publisher shall not be liable in any event of any damages, incidental or consequential, in
connection with, or arising out of the furnishing, performance or use of these programmes, procedures and functions. Produce name mentioned
are used for identification purposes only and may be trademarks of their respective companies.
All trademarks referred to in the book are acknowledged as properties of their respective owners.
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Dedicated to baba
Who couldn't be here to see this day…
About the Author
Through his books and online Quest Video Courses on C, C++, Data Structures, VC++, .NET, Embedded Systems, etc. Yashavant Kanetkar has
created, moulded and groomed lacs of IT careers in the last two and half decades. Yashavant's books and online courses have made a significant
contribution in creating top-notch IT manpower in India and abroad.
Yashavant's books are globally recognized and millions of students / professionals have benefitted from them. His books have been translated into
Hindi, Gujarati, Japanese, Korean and Chinese languages. Many of his books are published in India, USA, Japan, Singapore, Korea and China.
Yashavant is a much sought after speaker in the IT field and has conducted seminars/workshops at TedEx, IITs, NITs, IIITs and global software
companies.
Yashavant has been honored with the prestigious “Distinguished Alumnus Award” by IIT Kanpur for his entrepreneurial, professional and academic
excellence. This award was given to top 50 alumni of IIT Kanpur who have made significant contribution towards their profession and betterment of
society in the last 50 years.
In recognition of his immense contribution to IT education in India, he has been awarded the “Best .NET Technical Contributor” and “Most Valuable
Professional” awards by Microsoft for 5 successive years.
Yashavant holds a BE from VJTI Mumbai and M.Tech. from IIT Kanpur. His current affiliations include being a Director of KICIT Pvt. Ltd. He can be
reached at [e-mail] or through http://www.kicit.com.
Acknowledgments
Let Us C has become an important part of my life. I have created and nurtured it for last two decades. While doing so, I have received, in addition
to the compliments, a lot of suggestions from students, developers, professors, publishers and authors. So much have their inputs helped me in
taking this book up to its seventeenth edition that ideally I should put their names too on the cover page.
In particular, I am indebted to Manish Jain who had a faith in this book idea, believed in my writing ability, whispered the words of encouragement
and made helpful suggestions from time to time. I hope every author gets a publisher who is as cooperative, knowledgeable and supportive as
Manish.
The previous editions of this book saw several changes and facelifts. During this course many people helped in executing programs and spotting
bugs. I trust that with their collective acumen, all the programs in this book would run correctly. I value the work that they did a lot. Any errors,
omissions or inconsistencies that remain are, alas, my responsibility.
I thank all my family members for enduring the late nights, the clicking keyboard, and mostly for putting up with a marathon book effort.
Thinking of a book cover idea is one thing, putting it into action is a different cup of tea. This edition's cover idea has been implemented by Vinay
Indoria. Many thanks to him!
And finally my heartfelt gratitude to the countless students who made me look into every nook and cranny of C. I want to remain in their debt. It is
only because of them that Let Us C is now published from India, Singapore, USA, Japan, Dubai, Korea and China in multiple languages.
Preface
Let Us C has been part of learning and teaching material in most Engineering and Science Institutes round the country for years now. From last
year or so, I received several suggestions that its size be pruned a bit, as many learners who learn C language in their Engineering or Science
curriculum have some familiarity with it. I am happy to fulfill this request. I hope the readers would appreciate the lean look of the current edition.
In one of the previous edition I had realigned the chapters in such a manner that if a C programming course is taught using Let Us C, it can be
finished in 22 lectures of one hour each, with one chapter’s contents devoted to one lecture. I am happy that many readers liked this idea and
reported that this has made their learning path trouble-free. A more rational reorganization of end-of-chapter Exercises in the book has also been
well-received. Riding on that feedback I had introduced one more feature in the fifteenth edition—KanNotes. These are hand-crafted notes on C
programming. From the reader's emails I gather that they have turned out to be very useful to help revise their concepts on the day before the
examination, viva-voce or interview.
Many readers also told me that they have immensely benefitted from the inclusion of the chapter on Interview FAQs. I have improved this chapter
further. The rationale behind this chapter is simple—ultimately all the readers of Let Us C sooner or later end up in an interview room where they
are required to take questions on C programming. I now have a proof that this chapter has helped to make that journey smooth and fruitful.
In this edition I have added a separate section titled ‘Programs’ in each chapter. It contains interesting programs based on the topics covered in
the chapter. 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’. If you want some more problems for practice they are available in the book titled ‘Exploring C’. As usual,
new editions of these two books have also been launched along with 17th edition of Let Us C.
If you like ‘Let Us C’ and want to hear the complete video-recorded lectures created by me on C language (and other subjects like C++, VC++, C#,
Java, .NET, Embedded Systems, etc.), then you can visit http://quest.ksetindia.com for more details.
‘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 [e-mail] or [e-mail]
Countless Indians have relentlessly worked for close to three decades to successfully establish “India” as a software brand. At times, I take secret
pleasure in seeing that Let Us C has contributed in its own small little way in shaping so many careers that have made the “India” brand
acceptable.
Recently I was presented with “Distinguished Alumnus Award” by IIT Kanpur. It was great to figure in a list that contained Narayan Murthy, Chief
Mentor, Infosys, Dr. D. Subbarao, former Governor, Reserve Bank of India, Dr. Rajeev Motwani of Stanford University, Prof. H. C. Verma, Mr. Som
Mittal President of NASSCOM, Prof. Minwalla of Harvard University, Dr. Sanjay Dhande former Director of IIT Kanpur, Prof. Arvind and Prof. Sur of
MIT USA and Prof. Ashok Jhunjhunwala of IIT Chennai.
I think Let Us C amongst my other books has been primarily responsible for helping me get the “Distinguished Alumnus” award. What was a bit
surprising was that almost all who were present knew about the book already and wanted to know from me what it takes to write a book that sells in
millions of copies. My reply was—make an honest effort to make the reader understand what you have to say and keep it simple. I don't know how
convincing was this answer, but well, that is what I have been doing with this book in all its previous sixteen editions. I have followed the same
principle with this edition too.
All the best and happy programming!
Yashavant Kanetkar
Table of Contents
1. Getting Started
What is C?
Getting Started with C
Alphabets, Digits and Special Symbols
Constants, Variables and Keywords
Types of 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
Form of a C Program
Comments in a C Program
What is main() ?
Variables and their Usage
printf() and its Purpose
Compilation and Execution
Receiving Input
Programs
Exercises
KanNotes
1. C Instructions
Types of Instructions
Type Declaration Instruction
Arithmetic Instruction
Integer and Float Conversions
Type Conversion in Assignments
Hierarchy of Operations
Associativity of Operators
Control Instructions
Programs
Exercises
KanNotes
1. Decision Control Instruction
The if - else Statement
Multiple Statements within if - else
Nested if-else s
A Word of Caution
Programs
Exercises
KanNotes
1. More Complex Decision Making
Use of Logical Operators - Checking Ranges
The else if Clause
Use of Logical Operators - Yes / No Problem
The ! Operator
Hierarchy of Operators Revisited
The Conditional Operators
Programs
Exercises
KanNotes
1. Loop Control Instruction
Loops
The while Loop
Tips and Traps
More Operators
Programs
Exercises
KanNotes
1. More Complex Repetitions
The for Loop
Nesting of Loops
Multiple Initializations in the for Loop
The break Statement
The continue Statement
The do-while Loop
The Odd Loop
Programs
Exercises
KanNotes
1. Case Control Instruction
Decisions using switch
The Tips and Traps
switch versus if-else Ladder
The goto Keyword
Programs
Exercises
KanNotes
1. Functions
What is a Function?
Why use Functions?
Passing Values between Functions
Order of Passing Arguments
Using Library Functions
One Dicey Issue
Return Type of Function
Programs
Exercises
KanNotes
1. Pointers
Call by Value and Call by Reference
An Introduction to Pointers
Back to Function Calls
Conclusions
Programs
Exercises
KanNotes
1. Recursion
Recursion
Programs
Exercises
KanNotes
1. Data Types Revisited
Integers— long, short, signed , unsigned
Chars— signed, unsigned
Reals— float , double, long double
A Few More Issues…
Storage Classes in C
Automatic Storage Class
Register Storage Class
Static Storage Class
External Storage Class
A Few Subtle Issues
Which to Use When
Exercises
KanNotes
1. The C Preprocessor
Features of C Preprocessor
Macro Expansion
Macros with Arguments
Macros versus Functions
File Inclusion
Conditional Compilation
if and #elif Directives
Miscellaneous Directives
undef Directive
pragma Directive
The Build Process
Programs
Exercises
KanNotes
1. Arrays
What are Arrays?
A Simple Program using Array
More on Arrays
Array Initialization
Array Elements in Memory
Bounds Checking
Passing Array Elements to a Function
Pointers and Arrays
Accessing Array Elements using Pointers
Passing an Array to a Function
Flexible Arrays
Programs
Exercises
KanNotes
1. Multidimensional Arrays
Two-Dimensional Arrays
Initializing a 2-D Array
Memory Map of a 2-D Array
Pointers and 2-D Arrays
Pointer to an Array
Passing 2-D Array to a Function
Array of Pointers
3-D Array
Programs
Exercises
KanNotes
1. Strings
What are Strings
More about Strings
Pointers and Strings
Standard Library String Functions
strlen()
strcpy()
strcat()
strcmp()
Programs
Exercises
KanNotes
1. Handling Multiple Strings
2-D Array of Characters
Array of Pointers to Strings
Limitation of Array of Pointers to Strings
Programs
Exercises
KanNotes
1. Structures
Why use Structures?
Array of Structures
Intricacies of Structures
Structure Declaration
Storage of Structure Elements
Copying of Structure Elements
Nested Structures
Passing Structure Elements / Structure Variables
Packing Structure Elements
Uses of Structures
Programs
Exercises
KanNotes
1. Console Input/Output
Types of I/O
Console I/O Functions
Formatted Console I/O Functions
sprintf() and sscanf() Functions
Unformatted Console I/O Functions
Exercises
KanNotes
1. File Input/Output
File Operations
Opening a File
Reading from a File
Closing the File
Counting Characters, Tabs, Spaces, …
A File-Copy Program
File Opening Modes
String (Line) I/O in Files
Text Files and Binary Files
Record I/O in Files
Modifying Records
Low-Level File I/O
A Low-Level File-Copy Program
Programs
Exercises
KanNotes