C programming chapter 7

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 C Constants and Literals

The constants refer to fixed values that the program may not alter during its 

execution. These fixed values are also called literals.

Constants can be of any of the basic data types like an integer constant, a floating 

constant, a character constant, or a string literal. There are also enumeration 

constants as well.

The constants are treated just like regular variables except that their values cannot be 

modified after their definition.

Integer literals

An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the 

base or radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and 

long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Here are some examples of integer literals:

212 /* Legal */

215u /* Legal */

0xFeeL /* Legal */

078 /* Illegal: 8 is not an octal digit */

032UU /* Illegal: cannot repeat a suffix */

Following are other examples of various types of Integer literals:

85 /* decimal */

0213 /* octal */

0x4b /* hexadecimal */

30 /* int */

30u /* unsigned int */

30l /* long */

30ul /* unsigned long */

Floating-point literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an 

exponent part. You can represent floating point literals either in decimal form or 

exponential form.

While representing using decimal form, you must include the decimal point, the exponent, 

or both and while representing using exponential form, you must include the integer part, 

the fractional part, or both. The signed exponent is introduced by e or E.

Here are some examples of floating-point literals:

3.14159 /* Legal */

314159E-5L /* Legal */

510E /* Illegal: incomplete exponent */

210f /* Illegal: no decimal or exponent */

.e55 /* Illegal: missing integer or fraction */

Character constants

Character literals are enclosed in single quotes, e.g., 'x' and can be stored in a simple 

variable of char type.

A character literal can be a plain character (e.g., 'x'), an escape sequence (e.g., '\t'), or a 

universal character (e.g., '\u02C0').

There are certain characters in C when they are preceded by a backslash they will have 

special meaning and they are used to represent like newline (\n) or tab (\t). Here, you 

have a list of some of such escape sequence codes:

Escape 

sequence

Meaning

\\ \ character

\' ' character

\" " character

\? ? character

\a Alert or bell

\b Backspace

\f Form feed

\n Newline

\r Carriage return

\t Horizontal tab

\v Vertical tab

\ooo Octal number of one to three digits

\xhh . . . Hexadecimal number of one or more digits

Following is the example to show few escape sequence characters:

#include <stdio.h>

int main()

{

 printf("Hello\tWorld\n\n");

 return 0;

}

When the above code is compiled and executed, it produces the following result:

Hello World

String literals

String literals or constants are enclosed in double quotes "". A string contains characters 

that are similar to character literals: plain characters, escape sequences, and universal 

characters.

You can break a long line into multiple lines using string literals and separating them using 

whitespaces.

Here are some examples of string literals. All the three forms are identical strings.

"hello, dear"

"hello, \

dear"

"hello, " "d" "ear"

Defining Constants

There are two simple ways in C to define constants:

1. Using #define preprocessor.

2. Using const keyword.

The #define Preprocessor

Following is the form to use #define preprocessor to define a constant:

#define identifier value

Following example explains it in detail:

#include <stdio.h>

#define LENGTH 10 

#define WIDTH 5

#define NEWLINE '\n'

int main()

{

 int area; 

 

 area = LENGTH * WIDTH;

 printf("value of area : %d", area);

 printf("%c", NEWLINE);

 return 0;

}

When the above code is compiled and executed, it produces the following result:

value of area : 50

The const Keyword

You can use const prefix to declare constants with a specific type as follows:

const type variable = value;

Following example explains it in detail:

#include <stdio.h>

int main()

{

 const int LENGTH = 10;

 const int WIDTH = 5;

 const char NEWLINE = '\n';

 int area; 

 

 area = LENGTH * WIDTH;

 printf("value of area : %d", area);

 printf("%c", NEWLINE);

 return 0;

}

When the above code is compiled and executed, it produces the following result:

value of area : 50

Note that it is a good programming practice to define constants in CAPITALS.

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C programming chapter 6

  

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C programming chapter 6

C Variables

Avariable is nothing but a name given to a storage area that our programs can

manipulate. Each variable in C has a specific type, which determines the size and layout of 

the variable's memory; the range of values that can be stored within that memory; and the 

set of operations that can be applied to the variable.

The name of a variable can be composed of letters, digits, and the underscore character. It 

must begin with either a letter or an underscore. Upper and lowercase letters are distinct 

because C is case-sensitive. Based on the basic types explained in previous chapter, there 

will be the following basic variable types:

Type Description

Char Typically a single octet(one byte). This is an integer type.

Int The most natural size of integer for the machine.

Float A single-precision floating point value.

Double A double-precision floating point value.

Void Represents the absence of type.

C programming language also allows to define various other types of variables, which we 

will cover in subsequent chapters like Enumeration, Pointer, Array, Structure, Union, etc. 

For this chapter, let us study only basic variable types.

Variable Definition in C:

A variable definition means to tell the compiler where and how much to create the storage for the 

variable. A variable definition specifies a data type and contains a list of one or more variables of 

that type as follows:

type variable_list;

Here, type must be a valid C data type including char, w_char, int, float, double, bool or any user￾defined object, etc., and variable_list may consist of one or more identifier names separated by 

commas. Some valid declarations are shown here:

int i, j, k;

char c, ch;

float f, salary;

double d;

The line int i, j, k; both declares and defines the variables i, j and k; which instructs the compiler 

to create variables named i, j and k of type int.

Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of 

an equal sign followed by a constant expression as follows:

type variable_name = value;

Some examples are:

extern int d = 3, f = 5; // declaration of d and f.

int d = 3, f = 5; // definition and initializing d and f.

byte z = 22; // definition and initializes z.

char x = 'x'; // the variable x has the value 'x'.

For definition without an initializer: variables with static storage duration are implicitly initialized 

with NULL (all bytes have the value 0); the initial value of all other variables is undefined.

Variable Declaration in C:

A variable declaration provides assurance to the compiler that there is one variable existing with 

the given type and name so that compiler proceed for further compilation without needing 

complete detail about the variable. A variable declaration has its meaning at the time of 

compilation only, compiler needs actual variable declaration at the time of linking of the program.

A variable declaration is useful when you are using multiple files and you define your variable in 

one of the files, which will be available at the time of linking of the program. You will 

use extern keyword to declare a variable at any place. Though you can declare a variable multiple 

times in your C program but it can be defined only once in a file, a function or a block of code.

Example

Try the following example, where variables have been declared at the top, but they have been 

defined and initialized inside the main function:

#include <stdio.h>

// Variable definition:

extern int a, b;

extern int c;

extern float f;

int main ()

{

// Variable definition:

int a, b;

int c;

float f;

// actual initialization

 a =10;

 b =20;

 c = a + b;

 printf("value of c : %d \n", c);

 f = 70.0/3.0;

 printf("value of f : %f \n", f);

 return 0;

}

When the above code is compiled and executed, it produces the following result:

value of c : 30

value of f : 23.333334

Same concept applies on function declaration where you provide a function name at the time of its 

declaration and its actual definition can be given anywhere else. For example:

// function declaration

int func();

int main()

{ 

 // function call 

 int i = func();

} 

// function definition

int func()

{ 

 return 0;

}

Lvalues and Rvalues in C

There are two kinds of expressions in C:

1. lvalue: An expression that is an lvalue may appear as either the left-hand or right-hand 

side of an assignment.

2. rvalue: An expression that is an rvalue may appear on the right- but not left-hand side 

of an assignment.

Variables are lvalues and so may appear on the left-hand side of an assignment. Numeric 

literals are rvalues and so may not be assigned and cannot appear on the left-hand side. 

Following is a valid statement:

int g = 20;

But following is not a valid statement and would generate compile-time error:

10  -  20

C programming chapter 5

  

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Chapter 5

C Data Types

In the C programming language, data types refer to an extensive system used for 

declaring variables or functions of different types. The type of a variable determines how 

much space it occupies in storage and how the bit pattern stored is interpreted.

The types in C can be classified as follows:

S.N. Types and Description

1

Basic Types:

They are arithmetic types and consists of the two types: (a) integer types and (b) floating￾point types.

2

Enumerated types:

They are again arithmetic types and they are used to define variables that can only be 

assigned certain discrete integer values throughout the program.

3

The type void:

The type specifier void indicates that no value is available.

4

Derived types:

They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union types and 

(e) Function types.

The array types and structure types are referred to collectively as the aggregate types. The 

type of a function specifies the type of the function's return value. We will see basic types 

in the following section, whereas, other types will be covered in the upcoming chapters.

Integer Types

Following table gives you details about standard integer types with its storage sizes and 

value ranges:

Type Storage size Value range

Char 1 byte -128 to 127 or 0 to 255

unsigned char 1 byte 0 to 255

signed char 1 byte -128 to 127

Int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647

unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295

Short 2 bytes -32,768 to 32,767

unsigned short 2 bytes 0 to 65,535

Long 4 bytes -2,147,483,648 to 2,147,483,647

unsigned long 4 bytes 0 to 4,294,967,295

To get the exact size of a type or a variable on a particular platform, you can use 

the sizeof operator. The expressions sizeof(type) yields the storage size of the object or 

type in bytes. Following is an example to get the size of int type on any machine:

#include <stdio.h>

#include <limits.h>

int main()

{

 printf("Storage size for int : %d \n", sizeof(int));

 

 return 0;

}

When you compile and execute the above program, it produces the following result on 

Linux:

Storage size for int : 4

Floating-Point Types

Following table gives you details about standard floating-point types with storage sizes and 

value ranges and their precision:

Type Storage size Value range Precision

float 4 byte 1.2E-38 to 3.4E+38 6 decimal places

double 8 byte 2.3E-308 to 1.7E+308 15 decimal places

long double 10 byte 3.4E-4932 to 1.1E+4932 19 decimal places

The header file float.h defines macros that allow you to use these values and other details 

about the binary representation of real numbers in your programs. Following example will 

print storage space taken by a float type and its range values:

#include <stdio.h>

#include <float.h>

int main()

{

 printf("Storage size for float : %d \n", sizeof(float));

 printf("Minimum float positive value: %E\n", FLT_MIN );

 printf("Maximum float positive value: %E\n", FLT_MAX );

 printf("Precision value: %d\n", FLT_DIG );

 

 return 0;

}

When you compile and execute the above program, it produces the following result on 

Linux:

Storage size for float : 4

Minimum float positive value: 1.175494E-38

Maximum float positive value: 3.402823E+38

Precision value: 6

The void Type

The void type specifies that no value is available. It is used in three kinds of situations:

S.N. Types and Description

1

Function returns as void

There are various functions in C which do not return value or you can say they return void. 

A function with no return value has the return type as void. For example, void exit (int 

status);

2

Function arguments as void

There are various functions in C which do not accept any parameter. A function with no 

parameter can accept as a void. For example, int rand(void);

3

Pointers to void

A pointer of type void * represents the address of an object, but not its type. For example,

a memory allocation function void *malloc( size_t size ); returns a pointer to void which 

can be casted to any data type.

The void type may not be understood to you at this point, so let us proceed and we will 

cover these concepts in the upcoming chapters.

C programming chapter 3 and 4

 

C programming by UAH TECHTUBE

 C Program Structuretutorial.pdf

Let’s look into Hello World example using C Programming Language.

Before we study basic building blocks of the C programming language, let us look a 

bare minimum C program structure so that we can take it as a reference in upcoming 

chapters.

C Hello World Example

A C program basically consists of the following parts:

 Preprocessor Commands

 Functions

 Variables

 Statements & Expressions

 Comments

Let us look at a simple code that would print the words "Hello World":

#include <stdio.h>

int main()

{

 /* my first program in C */

 printf("Hello, World! \n");

 

 return 0;

}

Let us look various parts of the above program:

1. The first line of the program #include <stdio.h> is a preprocessor command, which tells 

a C compiler to include stdio.h file before going to actual compilation.

2. The next line int main() is the main function where program execution begins.

3. The next line /*...*/ will be ignored by the compiler and it has been put to add additional 

comments in the program. So such lines are called comments in the program.

4. The next line printf(...) is another function available in C which causes the message 

"Hello, World!" to be displayed on the screen.

5. The next line return 0; terminates main()function and returns the value 0.

Compile & Execute C Program

Let’s look at how to save the source code in a file, and how to compile and run it. Following 

are the simple steps:

1. Open a text editor and add the above-mentioned code.

2. Save the file as hello.c

3. Open a command prompt and go to the directory where you saved the file.

4. Type gcc hello.c and press enter to compile your code.

5. If there are no errors in your code, the command prompt will take you to the next line and 

would generate a.out executable file.

6. Now, type a.out to execute your program.

7. You will be able to see "Hello World" printed on the screen

$ gcc hello.c

$ ./a.out

Hello, World!

Make sure that gcc compiler is in your path and that you are running it in the directory 

containing source file hello.c.

C Basic Syntax

This chapter will give details about all the basic syntax about C programming language 

including tokens, keywords, identifiers, etc.

You have seen a basic structure of C program, so it will be easy to understand other 

basic building blocks of the C programming language.

Tokens in C

A C program consists of various tokens and a token is either a keyword, an identifier, a 

constant, a string literal, or a symbol. For example, the following C statement consists of 

five tokens:

printf("Hello, World! \n");

The individual tokens are:

printf

(

"Hello, World! \n"

)

;

Semicolons ;

In C program, the semicolon is a statement terminator. That is, each individual statement 

must be ended with a semicolon. It indicates the end of one logical entity.

For example, following are two different statements:

printf("Hello, World! \n");

return 0;

Comments

Comments are like helping text in your C program and they are ignored by the compiler. 

They start with /* and terminates with the characters */ as shown below:

/* my first program in C */

You cannot have comments within comments and they do not occur within a string or 

character literals.

Identifiers

A C identifier is a name used to identify a variable, function, or any other user-defined 

item. An identifier starts with a letter A to Z or a to z or an underscore _ followed by zero 

or more letters, underscores, and digits (0 to 9).

C does not allow punctuation characters such as @, $, and % within identifiers. C is a case 

sensitive programming language. Thus, Manpower and manpower are two different 

identifiers in C. Here are some examples of acceptable identifiers:

mohd zara abc move_name a_123

myname50 _temp j a23b9 retVal

Keywords

The following list shows the reserved words in C. These reserved words may not be used as 

constant or variable or any other identifier names.

auto else Long switch

break enum register typedef

case extern return union

char float short unsigned

const for signed void

continue goto sizeof volatile

default if static while

do int struct _packed

double

Whitespace in C

A line containing only whitespace, possibly with a comment, is known as a blank line, and a 

C compiler totally ignores it.

Whitespace is the term used in C to describe blanks, tabs, newline characters and 

comments. Whitespace separates one part of a statement from another and enables the 

compiler to identify where one element in a statement, such as int, ends and the next 

element begins. Therefore, in the following statement:

int age;

There must be at least one whitespace character (usually a space) between int and age for 

the compiler to be able to distinguish them. On the other hand, in the following statement:

fruit = apples + oranges; // get the total fruit

No whitespace characters are necessary between fruit and =, or between = and apples, 

although you are free to include some if you wish for readability purpose.

C programming chapter 1-3

 

                

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C programming chapter 1-3

C Language Overview

This chapter describes the basic details about C programming language, how it emerged, 

what are strengths of C and why we should use C.

The C programming language is a general-purpose, high-level language that was 

originally developed by Dennis M. Ritchie to develop the UNIX operating system at Bell 

Labs. C was originally first implemented on the DEC PDP-11 computer in 1972.

In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly available 

description of C, now known as the K&R standard.

The UNIX operating system, the C compiler, and essentially all UNIX applications programs 

have been written in C. The C has now become a widely used professional language for 

various reasons.

 Easy to learn

 Structured language

 It produces efficient programs.

 It can handle low-level activities.

 It can be compiled on a variety of computer platforms.

Facts about C

 C was invented to write an operating system called UNIX.

 C is a successor of B language, which was introduced around 1970.

 The language was formalized in 1988 by the American National Standard Institute.

(ANSI).

 The UNIX OS was totally written in C by 1973.

 Today, C is the most widely used and popular System Programming Language.

 Most of the state-of-the-art softwares have been implemented using C.

 Today's most ][popular Linux OS and RBDMS MySQL have been written in C.

Why to use C?

C was initially used for system development work, in particular the programs that make up 

the operating system. C was adopted as a system development language because it 

produces code that runs nearly as fast as code written in assembly language. Some 

examples of the use of C might be:

 Operating Systems

 Language Compilers

 Assemblers

 Text Editors

 Print Spoolers

 Network Drivers

 Modern Programs

 Databases

 Language Interpreters

 Utilities

C Programs

A C program can vary from 3 lines to millions of lines and it should be written into one or 

more text files with extension ".c"; for example, hello.c. You can use "vi", "vim" or any 

other text editor to write your C program into a file.

This tutorial assumes that you know how to edit a text file and how to write source code

using any programming language.

C Environment Setup

This section describes how to set up your system environment before you start doing your 

programming using C language.

Before you start doing programming using C programming language, you need the following 

two softwares available on your computer, (a) Text Editor and (b) The C Compiler.

Text Editor

This will be used to type your program. Examples of few editors include Windows Notepad, 

OS Edit command, Brief, Epsilon, EMACS, and vim or vi.

Name and version of text editor can vary on different operating systems. For example,

Notepad will be used on Windows, and vim or vi can be used on windows as well as Linux or 

UNIX.

The files you create with your editor are called source files and contain program source 

code. The source files for C programs are typically named with the extension “.c”.

Before starting your programming, make sure you have one text editor in place and you 

have enough experience to write a computer program, save it in a file, compile it and finally 

execute it.

The C Compiler

The source code written in source file is the human readable source for your program. It 

needs to be "compiled", to turn into machine language so that your CPU can actually 

execute the program as per instructions given.

This C programming language compiler will be used to compile your source code into final 

executable program. I assume you have basic knowledge about a programming language 

compiler.

Most frequently used and free available compiler is GNU C/C++ compiler, otherwise you can 

have compilers either from HP or Solaris if you have respective Operating Systems.

Following section guides you on how to install GNU C/C++ compiler on various OS. I'm 

mentioning C/C++ together because GNU gcc compiler works for both C and C++ 

programming languages.

Installation on UNIX/Linux

If you are using Linux or UNIX, then check whether GCC is installed on your system by 

entering the following command from the command line:

$ gcc -v

If you have GNU compiler installed on your machine, then it should print a message 

something as follows:

Using built-in specs.

Target: i386-redhat-linux

Configured with: ../configure --prefix=/usr .......

Thread model: posix

gcc version 4.1.2 20080704 (Red Hat 4.1.2-46)

If GCC is not installed, then you will have to install it yourself using the detailed 

instructions available athttp://gcc.gnu.org/install/

This tutorial has been written based on Linux and all the given examples have been 

compiled on Cent OS flavor of Linux system.

Installation on Mac OS

If you use Mac OS X, the easiest way to obtain GCC is to download the Xcode development 

environment from Apple's web site and follow the simple installation instructions. Once you 

have Xcode setup, you will be able to use GNU compiler for C/C++.

Xcode is currently available at developer.apple.com/technologies/tools/.

Installation on Windows

To install GCC at Windows you need to install MinGW. To install MinGW, go to the MinGW 

homepage, www.mingw.org, and follow the link to the MinGW download page. Download 

the latest version of the MinGW installation program, which should be named MinGW-

<version>.exe.

While installing MinWG, at a minimum, you must install gcc-core, gcc-g++, binutils, and 

the MinGW runtime, but you may wish to install more.

Add the bin subdirectory of your MinGW installation to your PATH environment variable, so 

that you can specify these tools on the command line by their simple names.

When the installation is complete, you will be able to run gcc, g++, ar, ranlib, dlltool, and 

several other GNU tools from the Windows command line.

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