EC2311-Data Structures and C Programming

Data Structures & C
Programming

C Programming
• What is C?
• C is a computer programming language used to design
computer software and applications.
• Why do we use C?
• We use the C programming language to design
computer software and applications.
• Who invented C?
• C Programming Language was invented in the year 1972
by Dennis Ritchie (Dennis MacAlistair Ritchie). He was
an American Computer Scientist worked at Bell Labs as
a researcher along with Ken Thompson. He was born on
9th September 1941 and lived till 12th October 2011.
He is said to be the Father of C.

Software used to create and execute a
C Program
• Following are the applications and software
used to create and execute C programs.
• Turbo C
• Turbo C++
• GNU C
• Code Blocks
• Net Beans

Computer Language
Computer languages are the languages through
which the user can communicate with the
computer by writing program instructions.

Creating and Running C Program
• File -> New Type the program Save it as FileName.c (Use shortcut key F2 to save)
• The compilation is the process of converting high-level language instructions into low-level
language instructions.
• The .exe file is submitted to the CPU, performs the task result generated in window screen
• Alt + F5 to open the User Screen and check the result.

Execution Process of a C Program

Important Points
• C program file (Source file) must save with .c extension.
• The compiler converts complete program at a time from
high-level language to low-level language.
• Input to the compiler is .c file and output from the compiler
is .exe file, but it also generates .obj file in this process.
• The compiler converts the file only if there are no errors in
the source code.
• CPU places the result in User Screen window.
Overall Process
• Type the program in C editor and save with .c
extension (Press F2 to save).
• Press Alt + F9 to compile the program.
• If there are errors, correct the errors and recompile the
program.
• If there are no errors, then press Ctrl + F9 to execute/run
the program.
• Press Alt + F5 to open User Screen and check the result.

C Programming Structure
• C is a structured programming language. Every c program and its statements must be in a
particular structure. Every c program has the following general structure...

#include <stdio.h>
int main()
{
printf("Hello World!");
return 0;
}

C Tokens
• In a C program, a collection of all the
keywords, identifiers, operators, special
symbols, constants, strings, and data values
are called tokens.

C Keywords
• Keywords are the reserved words with predefined meaning
which already known to the compiler.
• 32 keywords
• Properties of Keywords
• All the keywords in C programming language are defined as
lowercase letters so they must be used only in lowercase letters
• Every keyword has a specific meaning, users can not change that
meaning.
• Keywords can not be used as user-defined names like variable,
functions, arrays, pointers, etc...
• Every keyword in C programming language represents
something or specifies some kind of action to be performed by
the compiler.

C Identifiers
The identifier is a user-defined name of an entity to identify it
uniquely during the program execution
Example
int marks;
char studentName[30];
Here, marks and studentName are identifiers.
• Rules for Creating Identifiers
• A n i d e n t i f i e r c a n c o n t a i n l e t t e r s ( U P P E R C A S E a n d
lowercase), numerics & underscore symbol only.
• An identifier should not start with a numerical value. It can start with a letter or an
underscore.
• We should not use any special symbols in between the identifier even whitespace.
However, the only underscore symbol is allowed.
• Keywords should not be used as identifiers.
• There is no limit for the length of an identifier. However, the compiler considers the
first 31 characters only.
• An identifier must be unique in its scope.

• void data type
• The void data type means nothing or no value. Generally, the
void is used to specify a function which does not return any
value. We also use the void data type to specify empty
parameters of a function.
• Enumerated data type
• An enumerated data type is a user-defined data type that
consists of integer constants and each integer constant is given
a name. The keyword "enum" is used to define the
enumerated data type.
• Derived data types
• Derived data types are user-defined data types. The derived
data types are also called as user-defined data types or
secondary data types. In the c programming language, the
derived data types are created using the following concepts...
• Arrays
• Structures
• Unions
• Enumeration

C Variables
• Variable is a name given to a memory location where
we can store different values of the same datatype
during the program execution.
• A variable name may contain letters, digits and
underscore symbol. The following are the rules to
specify a variable name...
– Variable name should not start with a digit.
– Keywords should not be used as variable names.
– A variable name should not contain any special symbols
except underscore(_).
– A variable name can be of any length but compiler
considers only the first 31 characters of the variable name.

C Constants
• A constant is a named memory location which holds only
one value throughout the program execution.
• The specific alphabetical or numerical value that never gets
changed during the processing of the instructions is called
as constant.
• The constant can be alphabetical, numeric or special
symbol.
• The constants are given some names and are referred by
the names.
• Example: The most commonly used constant is PI. Once the
value to this constant is assigned then it does not get
changed.
• The names to the constant help in accessing them easily.
• Generally all the letters in the name of the constant are
capital.

C Output Functions
• C programming language provides built-in
functions to perform output operation. The
output operations are used to display data on
user screen (output screen) or printer or any file.
The c programming language provides the
following built-in output functions...
• printf()
• putchar()
• puts()
• fprintf()

General rules for any C program
• Every executable statement must end with a
semicolon symbol (;).
• Every C program must contain exactly one main
method (Starting point of the program execution).
• All the system-defined words (keywords) must be
used in lowercase letters.
• Keywords can not be used as user-defined
names(identifiers).
• For every open brace ({), there must be respective
closing brace (}).
• Every variable must be declared before it is used.

printf("message to be display!!!");
#include <stdio.h> //this is needed to run printf() function.
int main()
{
printf("Hello World!"); // displays the contents inside “”
return 0;
}

printf("format string",variableName);

printf("String format string",variableName);

C Input Functions
• C programming language provides built-in
functions to perform input operations. The input
operations are used to read user values (input)
from the keyboard. The c programming language
provides the following built-in input functions.
• scanf()
• getchar()
• getch()
• gets()
• fscanf()

scanf() function
• The scanf() function is used to read multiple data values of different data
types from the keyboard. The scanf() function is built-in function defined
in a header file called "stdio.h". When we want to use scanf() function in
our program, we need to include the respective header file (stdio.h)
using #include statement. The scanf() function has the following syntax...
• scanf("format strings",&variableNames);

getchar() function
The getchar() function is used to read a character from the keyboard and return it to the program.This
function is used to read a single character. To read multiple characters we need to write multiple
times or use a looping statement.

getch() function
• The getch() function is similar to getchar function. The getch() function is
used to read a character from the keyboard and return it to the program.
This function is used to read a single character. To read multiple characters
we need to write multiple times or use a looping statement.

gets() function
• The gets() function is used to read a line of string and stores it into a
character array. The gets() function reads a line of string or sequence of
characters till a newline symbol enters.

fscanf() function
• The fscanf() function is used with the concept
of files. The fscanf() function is used to read
data values from a file. When you want to use
fscanf() function the file must be opened in
reading mode.

C Operators
• An operator is a symbol used to perform arithmetic and logical
operations in a program. That means an operator is a special
symbol that tells the compiler to perform mathematical or logical
operations. C programming language supports a rich set of
operators that are classified as follows.
• Arithmetic Operators
• Relational Operators
• Logical Operators
• Increment & Decrement Operators
• Assignment Operators
• Bitwise Operators
• Conditional Operator
• Special Operators

Arithmetic Operators (+, -, *, /, %)
• The arithmetic operators are the symbols that are used to perform basic
mathematical operations like addition, subtraction, multiplication, division and
percentage modulo. The following table provides information about arithmetic
operators.

Relational Operators (<, >, <=, >=,
==, !=)
• The relational operators are the symbols that are used to compare two values.
That means the relational operators are used to check the relationship between
two values. Every relational operator has two results TRUE or FALSE. In simple
words, the relational operators are used to define conditions in a program. The
following table provides information about relational operators.

Logical Operators (&&, ||, !)
• The logical operators are the symbols that are used to
combine multiple conditions into one condition. The following
table provides information about logical operators.

Increment & Decrement
Operators (++ & --)
• The increment and decrement operators are called unary operators because both
need only one operand. The increment operators adds one to the existing value of
the operand and the decrement operator subtracts one from the existing value of
the operand. The following table provides information about increment and
decrement operators.

Assignment Operators (=, +=, -=, *=,
/=, %=)
• The assignment operators are used to assign right-hand side value (Rvalue) to the
left-hand side variable (Lvalue). The assignment operator is used in different
variants along with arithmetic operators. The following table describes all the
assignment operators in the C programming language.

Bitwise Operators (&, |, ^, ~, >>, <<)
• The bitwise operators are used to perform bit-level operations in the c
programming language. When we use the bitwise operators, the operations are
performed based on the binary values. The following table describes all the bitwise
operators in the C programming language.
Let us consider two variables A and B as A = 25 (11001) and B = 20 (10100).

Conditional Operator (?:)
• The conditional operator is also called a ternary
operator because it requires three operands. This
operator is used for decision making. In this operator,
first we verify a condition, then we perform one
operation out of the two operations based on the
condition result. If the condition is TRUE the first option
is performed, if the condition is FALSE the second option
is performed. The conditional operator is used with the
following syntax.
Condition ? TRUE Part : FALSE Part;
Example
• A = (10<15)?100:200; ⇒ A value is 100

Special Operators (sizeof, pointer,
comma, dot, etc.)
• The following are the special operators in c programming language.
• sizeof operator
• This operator is used to find the size of the memory (in bytes) allocated for
a variable. This operator is used with the following syntax.
• sizeof(variableName);
Example
• sizeof(A); ⇒ the result is 2 if A is an integer
• Pointer operator (*)
• This operator is used to define pointer variables in c programming
language.
• Comma operator (,)
• This operator is used to separate variables while they are declaring,
separate the expressions in function calls, etc.
• Dot operator (.)
• This operator is used to access members of structure or union.

C Expressions
An expression is a collection of operators and
operands that represents a specific value.
->An operator is a symbol that performs tasks like
arithmetic operations, logical operations, and
conditional operations, etc.
->Operands are the values on which the
operators perform the task. Here operand can be
a direct value or variable or address of memory
location.

Expression Types in C
• In the C programming language, expressions
are divided into THREE types. They are as
follows...
• Infix Expression
• Postfix Expression
• Prefix Expression

Infix Expression
• The expression in which the operator is used between
operands is called infix expression.
The infix expression has the following general structure.
• Operand1 Operator Operand2

Postfix Expression
• The expression in which the operator is used after operands is called
postfix expression.
The postfix expression has the following general structure.
• Operand1 Operand2 Operator

Prefix Expression
• The expression in which the operator is used before operands is called a
prefix expression.
The prefix expression has the following general structure.
• Operator Operand1 Operand2

C Operator Precedence
• Operator precedence is used to determine the
order of operators evaluated in an expression.
In c programming language every operator has
precedence (priority). When there is more
than one operator in an expression the
operator with higher precedence is evaluated
first and the operator with the least
precedence is evaluated last.

Decision Making Statement
• In the C programming language, the program
execution flow is line by line from top to
bottom. But this type of execution flow may
not be suitable for all the program solutions.

if statement in c
• In c, if statement is used to make decisions based
on a condition. The if statement verifies the given
condition and decides whether a block of
statements are executed or not based on the
condition result. In c, if statement is classified
into four types as follows...
• Simple if statement
• if-else statement
• Nested if statement
• if-else-if statement (if-else ladder)

Simple if statement
• Simple if statement is used to verify the given condition and executes the block of statements
based on the condition result. The simple if statement evaluates specified condition. If it is
TRUE, it executes the next statement or block of statements. If the condition is FALSE, it skips
the execution of the next statement or block of statements.
Simple if statement is used when we have only
one option that is executed or skipped based
on a condition.

Example Program | Test whether given number is divisible by 5.

if-else statement
• The if-else statement is used to verify the given condition and executes only one out of the
two blocks of statements based on the condition result. The if-else statement evaluates the
specified condition. If it is TRUE, it executes a block of statements (True block). If the
condition is FALSE, it executes another block of statements (False block).
The if-else statement is used when we have two options and only one
option has to be executed based on a condition result (TRUE or FALSE).

Example Program | Test whether given number is even or odd.

Nested if statement
• Writing a if statement inside another if statement is called nested if statement.
The nested if statement can be defined using any
combination of simple if & if-else statements.

Example Program | Test whether given number is
even or odd if it is below 100.

if-else-if statement (if-else ladder)
• Writing a if statement inside else of an if statement is called if-else-if
statement.
The if-else-if statement can be defined using any combination
of simple if & if-else statements.

Example Program | Find the largest of three
numbers.

• When we use a conditional control statement
like if statement, the condition might be an
expression evaluated to a numerical value, a
variable or a direct numerical value.
• If the expression value or direct value is zero the
condition becomes FALSE otherwise becomes
TRUE.

'switch' statement in C
• Consider a situation in which we have many options out of
which we need to select only one option that is to be
executed. Such kind of problems can be solved
using nested if statement. But as the number of options
increases, the complexity of the program also gets
increased. This type of problem can be solved very easily
using a switch statement. Using the switch statement, one
can select only one option from more number of options
very easily. In the switch statement, we provide a value that
is to be compared with a value associated with each option.
Whenever the given value matches the value associated
with an option, the execution starts from that option. In the
switch statement, every option is defined as a case.

• The switch statement contains one or more cases and each
case has a value associated with it.
• At first switch statement compares the first case value with
the switchValue, if it gets matched the execution starts
from the first case.
• If it doesn't match the switch statement compares the
second case value with the switchValue and if it is matched
the execution starts from the second case.
• This process continues until it finds a match. If no case
value matches with the switchValue specified in the switch
statement, then a special case called default is executed.
• When a case value matches with the switchValue, the
execution starts from that particular case. This execution
flow continues with the next case statements also.
• To avoid this, we use the "break" statement at the end of
each case. That means the break statement is used to
terminate the switch statement. However, it is optional.

Example Program | Display pressed digit in words.

When we use switch statement, we must follow the following...
• Both switch and case are keywords so they must be used only in
lower case letters.
• The data type of case value and the value specified in the switch
statement must be the same.
• switch and case values must be either integer or character but not
float or string.
• A switch statement can contain any number of cases.
• The keyword case and its value must be superated with a white
space.
• The case values need not be defined in sequence, they can be in
any order.
• The default case is optional and it can be defined anywhere inside
the switch statement.
• The switch value might be direct, a variable or an expression.

Looping statement in C
The looping statements are used to execute a
single statement or block of statements
repeatedly until the given condition is FALSE.
C language provides three looping statements...
• while statement
• do-while statement
• for statement

while Statement
The while statement is used to execute a single statement or block of
statements repeatedly as long as the given condition is TRUE. The while
statement is also known as Entry control looping statement.

When we use a while statement, we must follow the following...
• while is a keyword so it must be used only in lower case
letters.
• If the condition contains a variable, it must be assigned a
value before it is used.
• The value of the variable used in condition must be modified
according to the requirement inside the while block.
• In a while statement, the condition may be a direct integer
value, a variable or a condition.
• A while statement can be an empty statement.

'do-while' statement in C
• The do-while statement is used to execute a single statement or block of
statements repeatedly as long as given the condition is TRUE. The do-while
statement is also known as the Exit control looping statement.

When we use the do-while statement, we must follow
the following...
• Both do and while are keywords so they must be used
only in lower case letters.
• If the condition contains a variable, it must be assigned
a value before it is used.
• The value of the variable used in the condition must be
modified according to the requirement inside the do
block.
• In a do-while statement, the condition may be a direct
integer value, a variable or a condition.
• A do-while statement can be an empty statement.
• In do-while, the block of statements is executed at
least once.

'for' statement in C
• The for statement is used to execute a single statement or a block of
statements repeatedly as long as the given condition is TRUE.

When we use for statement, we must follow the
following...
• for is a keyword so it must be used only in lower case
letters.
• Every for statement must be provided with initialization,
condition, and modification (They can be empty but must
b e s e p a r a t e d w i t h " ; " )
Ex: for ( ; ; ) or for ( ; condition ; modification ) or for ( ;
condition ; )
• In for statement, the condition may be a direct integer
value, a variable or a condition.
• The for statement can be an empty statement.

break, continue and goto in C
• In c, there are control statements that do not
need any condition to control the program
execution flow. These control statements are
called as unconditional control statements. C
programming language provides the following
unconditional control statements...
• break
• continue
• goto
• The above three statements do not need any
condition to control the program execution flow.

break statement
• In C, the break statement is used to perform the
following two things...
• break statement is used to terminate the switch
case statement
• break statement is also used to terminate
looping statements like while, do-while and for.
• When a break statement is encountered inside
the switch case statement, the execution control
moves out of the switch statement directly.

• When the break statement is encountered inside the looping statement,
the execution control moves out of the looping statements.

continue statement
• The continue statement is used to move the program
execution control to the beginning of the looping statement.
When the continue statement is encountered in a looping
statement, the execution control skips the rest of the
statements in the looping block and directly jumps to the
beginning of the loop. The continue statement can be used
with looping statements like while, do-while and for.
• When we use continue statement with while and do-
while statements the execution control directly jumps to
the condition. When we use continue statement
with for statement the execution control directly jumps to
the modification portion (increment/decrement/any
modification) of the for loop.

goto statement
The goto statement is used to jump from one line to another line in the program.
Using goto statement we can jump from top to bottom or bottom to top. To jump from one
line to another line, the goto statement requires a label. Label is a name given to the
instruction or line in the program. When we use a goto statement in the program, the
execution control directly jumps to the line with the specified label.

When we use break, continue and goto statements, we must follow the following...
• The break is a keyword so it must be used only in lower case letters.
• The break statement can not be used with if statement.
• The break statement can be used only in switch case and looping statements.
• The break statement can be used with if statement, only if that if statement is
written inside the switch case or looping statements.
• The continue is a keyword so it must be used only in lower case letters.
• The continue statement is used only within looping statements.
• The continue statement can be used with if statement, only if that if
statement is written inside the looping statements.
• The goto is a keyword so it must be used only in lower case letters.
• The goto statement must require a label.
• The goto statement can be used with any statement like if, switch, while, do-
while, and for, etc.

Functions in C
Function is a subpart of a program used to
perform a specific task and is executed
individually.
Functions are used to divide a larger program
into smaller subprograms such that the
program becomes easy to understand and
easy to implement.

Every function in C has the following...
• Function Declaration (Function Prototype)
• Function Definition
• Function Call

Function Declaration
The function declaration tells the compiler about
function name, the data type of the return value and
parameters. The function declaration is also called a
function prototype.
• Function declaration syntax -
returnType functionName(parametersList);
• In the above syntax, returnType specifies the data type
of the value which is sent as a return value from the
function definition. The functionName is a user-
defined name used to identify the function uniquely in
the program. The parametersList is the data values
that are sent to the function definition.

Function Definition
• The function definition provides the actual code of that function.
The function definition is also known as the body of the function.
The actual task of the function is implemented in the function
definition. That means the actual instructions to be performed by a
function are written in function definition. The actual instructions
of a function are written inside the braces "{ }". The function
definition is performed before the main function or after the main
function.
• Function definition syntax -
returnType
functionName(parametersList)
{
Actual code...
}

Function Call
• The function call tells the compiler when to
execute the function definition. When a function
call is executed, the execution control jumps to
the function definition where the actual code
gets executed and returns to the same functions
call once the execution completes. The function
call is performed inside the main function or any
other function or inside the function itself.
• Function call syntax -
functionName(parameters);

ADVANTAGES OF FUNCTIONS
• Using funcions we can implement modular
programming.
• Functions make the program more readable and
understandable.
• Using functions the program implementation
becomes easy.
• Once a function is created it can be used many
times (code re-usability).
• Using functions larger programs can be divided
into smaller modules.

Types of Functions in C
• In C Programming Language, based on
providing the function definition, functions
are divided into two types. Those are as
follows...
• System Defined Functions
• User Defined Functions

System Defined Functions
• The C Programming Language provides pre-defined functions to make
programming easy. These pre-defined functions are known as system defined
functions. The system defined function is defined as follows...
• The function whose definition is defined by the system is called as system
defined function.
• The system defined functions are also called as Library Functions or Standard
Functions or Pre-Defined Functions. The implementation of system defined
functions is already defined by the system.
• In C, all the system defined functions are defined inside the header
files like stdio.h, conio.h, math.h, string.h etc., For example, the
funtions printf() and scanf() are defined in the header file called stdio.h.
• Whenever we use system defined functions in the program, we must include the
respective header file using #include statement. For example, if we use a system
defined function sqrt() in the program, we must include the header file
called math.h because the function sqrt() is defined in math.h.
• System defined functions are declared in header files
• System defined functions are implemented in .dll files. (DLL stands for Dynamic
Link Library).
• To use system defined functions the respective header file must be included.

User Defined Functions
• The function whose definition is defined by
the user is called as user defined function.
• Function without Parameters and without Return value
• Function with Parameters and without Return value
• Function without Parameters and with Return value
• Function with Parameters and with Return value

Function without Parameters and without Return value
• In this type of functions
there is no data transfer
between calling function
and called function. Simply
the execution control
j u m p s f r o m c a l l i n g -
function to called function
a n d e xe c u t e s c a l l e d
function, and finally comes
back to the calling function.

Function with Parameters and without Return
value
there is data transfer from
calling-function to called
function (parameters) but
from called function to
calling-function (return
value). The execution
control jumps from calling-
along with the parameters
a n d exe c u t e s c a l l e d
function, and finally comes
b a c k t o t h e c a l l i n g
function.

Function without Parameters and with Return
value
from calling-function to
c a l l e d - f u n c t i o n
(parameters) but there is
data transfer from called
function to calling-
function (return value).
The execution control
jumps from calling-
f u n c t i o n t o c a l l e d
function and executes
called function, and
finally comes back to the
calling function along
with a return value.

Function with Parameters and with Return value
there is data transfer from
calling-function to called-
function (parameters) and
also from called function
to calling-function (return
value). The execution
control jumps from calling-
along with parameters and
executes called function,
and finally comes back to
the calling function along
with a return value.

Points to be Remembered
• The parameters specified in calling function
are said to be Actual Parameters.
• The parameters declared in called function are
said to be Formal Parameters.
• The value of actual parameters is always
copied into formal parameters.

Parameter Passing in C
• When the execution control is transferred from calling-function
to called-function it may carry one or number of data values.
These data values are called as parameters.
• Parameters are the data values that are passed from calling
function to called function.
• In C, there are two types of parameters and they are as
follows...
• Actual Parameters
• Formal Parameters
• The actual parameters are the parameters that are speficified
in calling function. The formal parameters are the parameters
that are declared at called function. When a function gets
executed, the copy of actual parameter values are copied into
formal parameters.
• In C Programming Language, there are two methods to pass
parameters from calling function to called function and they
are as follows...
• Call by Value
• Call by Reference

Call by Value
• In call by value parameter
passing method, the copy of
actual parameter values are
copied to formal parameters
and these formal parameters
are used in called function. The
changes made on the formal
parameters does not effect the
values of actual parameters.
That means, after the execution
control comes back to the
calling function, the actual
parameter values remains
same.

Call by Reference
• In Call by Reference parameter
passing method, the memory
location address of the actual
parameters is copied to formal
parameters. This address is used to
access the memory locations of the
actual parameters in called function.
In this method of parameter passing,
t h e fo r m a l p a ra m ete rs m u st
be pointer variables.
• That means in call by reference
parameter passing method, the
address of the actual parameters is
passed to the called function and is
received by the formal parameters
(pointers). Whenever we use these
formal parameters in called function,
they directly access the memory
locations of actual parameters.
So the changes made on the formal
parameters effects the values of
actual parameters.

Scope of Variable in C
• Scope of a variable is the portion of the program
where a defined variable can be accessed.
• Before the function definition (Global
Declaration)
• Inside the function or block (Local Declaration)
• In the function definition parameters (Formal
Parameters)

Recursive Functions in C
• In C programming language, function calls can be made
from the main() function, other functions or from the same
function itself.
A function called by itself is called recursive function.
• The recursive functions should be used very carefully
because, when a function called by itself it enters into the
infinite loop. And when a function enters into the infinite
loop, the function execution never gets completed. We
should define the condition to exit from the function call so
that the recursive function gets terminated.
• When a function is called by itself, the first call remains
under execution till the last call gets invoked. Every time
when a function call is invoked, the function returns the
execution control to the previous function call.

Arrays in C
• An array is a special type of variable used to
store multiple values of same data type at a
time.
• An array is a collection of similar data items
stored in continuous memory locations with
single name.

Declaration of an Array
• In C programming language, when we want to create an
array we must know the datatype of values to be stored in
that array and also the number of values to be stored in
that array.
We use the following general syntax to create an array...
• datatype arrayName [ size ] ;
• Syntax for creating an array with size and initial values
• datatype arrayName [ size ] = {value1, value2, ...} ;
• Syntax for creating an array without size and with initial
values
• datatype arrayName [ ] = {value1, value2, ...} ;
• In the above syntax, the datatype specifies the type of
values we store in that array and size specifies the
maximum number of values that can be stored in that array.

• Example Code
•int a [3] ;
• Here, the compiler allocates 6 bytes of contiguous memory
locations with a single name 'a' and tells the compiler to store
three different integer values (each in 2 bytes of memory) into
that 6 bytes of memory.
• In the above memory allocation, all the three memory
locations have a common name 'a'. So accessing individual
memory location is not possible directly. Hence compiler not
only allocates the memory but also assigns a numerical
reference value to every individual memory location of an
array. This reference number is called "Index" or "subscript" or
"indices".

Accessing Individual Elements of an
Array
arrayName [ indexValue ] ;

Types of Arrays in C
• Single Dimensional Array / One Dimensional
Array
• Multi Dimensional Array

Single Dimensional Array
• single dimensional arrays are used to store list of values of same datatype.
• In other words, single dimensional arrays are used to store a row of values.
In single dimensional array, data is stored in linear form.
• Single dimensional arrays are also called as one-dimensional arrays, Linear
Arrays or simply 1-D Arrays.
• Declaration of Single Dimensional Array
• We use the following general syntax for declaring a single dimensional
array...
• datatype arrayName [ size ] ;
• Example Code
• int rollNumbers [60] ;
• The above declaration of single dimensional array reserves 60 continuous
memory locations of 2 bytes each with the name rollNumbers and tells
the compiler to allow only integer values into those memory locations.

Initialization of Single Dimensional
Array
• We use the following general syntax for declaring and initializing a
single dimensional array with size and initial values.
• datatype arrayName [ size ] = {value1, value2, ...} ;
• Example Code
• int marks [6] = { 89, 90, 76, 78, 98, 86 } ;
• The above declaration of single dimensional array reserves 6
contiguous memory locations of 2 bytes each with the
name marks and initializes with value 89 in first memory location,
90 in second memory location, 76 in third memory location, 78 in
fourth memory location, 98 in fifth memory location and 86 in sixth
memory location.
• We can also use the following general syntax to intialize a single
dimensional array without specifying size and with initial values...
• datatype arrayName [ ] = {value1, value2, ...} ;
• The array must be initialized if it is created without specifying any
size. In this case, the size of the array is decided based on the
number of values initialized.

• Example Code
int marks [] = { 89, 90, 76, 78, 98, 86 } ;
char studentName [] = "btechsmartclass" ;
• In the above example declaration, size of the
array 'marks' is 6 and the size of the
array 'studentName' is 16. This is because in
case of character array, compiler stores one
exttra character called 0 (NULL) at the end.

Accessing Elements of Single
Dimensional Array
• In c programming language, to access the elements of single dimensional
array we use array name followed by index value of the element that to be
accessed. Here the index value must be enclosed in square
braces. Index value of an element in an array is the reference number
given to each element at the time of memory allocation. The index value
of single dimensional array starts with zero (0) for first element and
incremented by one for each element. The index value in an array is also
called as subscript or indices.
We use the following general syntax to access individual elements of single
dimensional array...
• arrayName [ indexValue ]
• Example Code
• marks [2] = 99 ;
• In the above statement, the third element of 'marks' array is assinged with
value '99'.

Multi Dimensional Array
• An array of arrays is called as multi dimensional array. In simple
words, an array created with more than one dimension (size) is
called as multi dimensional array. Multi dimensional array can be
of two dimensional array or three dimensional array or four
dimensional array or more...
Most popular and commonly used multi dimensional array is two
dimensional array. The 2-D arrays are used to store data in the
form of table. We also use 2-D arrays to create
mathematical matrices.
• Declaration of Two Dimensional Array
• We use the following general syntax for declaring a two dimensional
array...
– datatype arrayName [ rowSize ] [ columnSize ] ;
• Example Code
• int matrix_A [2][3] ;
• The above declaration of two dimensional array reserves 6
continuous memory locations of 2 bytes each in the form of 2
rows and 3 columns.

Initialization of Two Dimensional
Array
• We use the following general syntax for declaring and
initializing a two dimensional array with specific
number of rows and coloumns with initial values.
• datatype arrayName [rows][colmns] = {{r1c1value,
r1c2value, ...},{r2c1, r2c2,...}...} ;
• Example Code
• int matrix_A [2][3] = { {1, 2, 3},{4, 5, 6} } ;
• The above declaration of two-dimensional array
reserves 6 contiguous memory locations of 2 bytes
each in the form of 2 rows and 3 columns. And the first
row is initialized with values 1, 2 & 3 and second row is
initialized with values 4, 5 & 6.

Accessing Individual Elements of Two
Dimensional Array
• In a c programming language, to access elements of a two-
dimensional array we use array name followed by row index value
and column index value of the element that to be accessed. Here
the row and column index values must be enclosed in separate
square braces. In case of the two-dimensional array the compiler
assigns separate index values for rows and columns.
We use the following general syntax to access the individual
elements of a two-dimensional array...
• arrayName [ rowIndex ] [ columnIndex ]
• Example Code
• matrix_A [0][1] = 10 ;
• In the above statement, the element with row index 0 and column
index 1 of matrix_A array is assinged with value 10.

Applications of Arrays in C
● Arrays are used to Store List of values
In c programming language, single dimensional arrays are used to store list of
values of same datatype. In other words, single dimensional arrays are used
to store a row of values. In single dimensional array data is stored in linear
form.
● Arrays are used to Perform Matrix Operations
We use two dimensional arrays to create matrix. We can perform various
operations on matrices using two dimensional arrays.
● Arrays are used to implement Search Algorithms
We use single dimensional arrays to implement search algorihtms like ...
Linear Search,Binary Search
● Arrays are used to implement Sorting Algorithms
We use single dimensional arrays to implement sorting algorihtms like ...
Insertion Sort,Bubble Sort,Selection Sort,Quick Sort,Merge Sort, etc.,
● Arrays are used to implement Datastructures
We use single dimensional arrays to implement datastructures like...
Stack Using Arrays,Queue Using Arrays
● Arrays are also used to implement CPU Scheduling Algorithms

EC2311-Data Structures and C Programming

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EC2311-Data Structures and C Programming