U3.pptx

Unit III
Arrays and Pointers
L.NIVETHA AP/CSE,KNCET

Introduction to Arrays – Single
Dimensional Arrays – Multidimensional
Array – Pointers – void Pointer – Null
Pointer – Relationship between Arrays
and Pointers – Arrays of Pointers –
Pointer to a Pointer – Pointer to an Array.

ARRAYS & its types
Presented by,
L.Nivetha,AP/CSE,
KNCET
KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY
(AUTONOMOUS)
NAMAKKAL - TRICHY MAIN ROAD, THOTTIAM, TRICHY-621 215

ARRAY - Definition
 An array is a data structure, that is
used to store the homogeneous data.
 An array is a collection of similar data
items that are stored under a common
name.
 A value in an array is identified by it’s
index or subscript.
 subscript enclosed in square brackets
with an array name.
 Array is derived data type

Types of Array
Array can be classified into:
• One dimensional Array
• Two dimensional Array
• Multi dimensional Array

1. One Dimensional Array
 The collection of data items can be stored
under a single variable name using only one
subscript
 so such a variable called one dimensional
Array.
 It store fixed number of elements with same
data type.
 It is organized in a linear sequence.
 It is also named as linear array and vector.

Array Declaration:
Array are declared in the same manner as an
ordinary variables except that each array name must
have one subscript.
Syntax:
data type array_variable[size or subscript of the
array];
Example:
• int a[5];
a[0]
a[1]
a[2]
a[3]
a[4]

Array Initialization
The value can be initialized to an array,
when they are declared like ordinary
variables. Otherwise they hold garbage
value.
The array can be initialized into two way’s:
1. At compile time
2. At run time

At compile time:
syntax: data type array_name[size] =
{list of values}
Example: int marks[3] = {98,67,97};
(or)
marks[0]=98;
marks[1]=67;
marks[2]=97;

Example Program:
#include<stdio.h>
#include<conio.h>
void main()
{
int b[3] = {2,4,5} , i ;
clrscr();
for(i=0; i<3 ;i++)
{
Printf(“%d”, b[i]);
}
}

At run time initialization:
The array can be explicitly initialized at run
time.
Here we use the for loop as well as scanf()
statement to get a value of an array variable.
Example:1
int n[3],i;
for(i=0 ; i<3 ; i++)
{
scanf( “%d”, &n[i] );
}

Example program:
#include<stdio.h>
void main()
{
int mark[3], i;
printf(“enter the marks:”);
for(i=0 ; i<3 ; i++)
{
scanf( “%d”, &mark[i] );
}
for(i=0 ; i<3 ; i++)
{
printf( “%d”, mark[i] );
}
}

Assigning an array to another array:
To assign the one array element into another
array by using it’s index position.
 Here not possible to assign array1=array2.
 variable only possible to assign like this
assignment.
Example :
int a[3], b[3]={2,4,6}, i;
for(i=0;i<3;i++)
a[i]=b[i]

Two Dimensional Array
The array variable declared using two
subscript then it is called as two dimensional
array.
Two dimensional array are used to store table
of values also called as matrix.
It’s element arranged in rectangular grid of
rows and column.
to access this data by using both column and
row subscript.

Declaring two dimensional array
To declare the two dimensional array with two
subscript.
First subscript with row size and 2nd subscript
with column size.
data type and identifier with row and column
subscript are mandatory.

Syntax:
data_type array_name[row size][column size];
Example:
int a[3][3];
col0 col1 col2
Row0
Row1
Row2
A[0][0] A[0][1] A[0][2]
A[1][0] A[1][1] A[1][2]
A[2][0] A[2][1] A[2][2]

Initializing a two dimensional array:
To initialize two dimensional array like one
dimensional array
The number of values initialize in an array is
less than or equal to array size(row size * column
size)
Example:
int a[2][2]={
{23,34},
{43,45},
};
Or
int a[2][2]={89,10,34,34};

Example Program:
#include<stdio.h>
#include<conio.h>
void main()
{ 0 1
int s[3][2]= {0{ 23,34 },
1{ 45,45 },
2{ 76,86 } }
int i , j ;
clrscr();
for(i=0;i<3;i++)
{
for(j=0;j<2;j++)
{
printf(“%d”, s[i][j]);
}
printf(“n”);
}
}

Multidimensional Array
If a variable having more than two
subscript then those array variable is called as
multidimensional array
three dimensional arrays can be visualized
as a cube that has a number of planes
Each plane is a two dimensional arrays, so
we made a three dimensional array using
many two dimensional array.

Declaring three dimensional array:
plane, row and column specifier are compile
time constant, it must be greater than zero.
Syntax:
data_type
array_variable[plane_specifier][row_specifier]
[column_specifier];
Example
Int a[2][5][3];

Int a;
a= 15;
Int *b;
b=&a;

POINTER
Pointer is a variable that contains
memory address of a normal variable or a
function.
it is a derived data type in C language.
pointer can be used to access and
manipulate data stored in the memory.

Pointer allow dynamic memory management
Pointers provide an efficient tool for
manipulating dynamic data structure
such as structures , linked list , queues ,
stacks and trees.
Pointer reduce length and complexity of the
program.
Advantages of pointer

 pointer variable declaration is same as normal variable
declaration ,
 In additionally we add ‘*’symbol before the variable
name then that variable called pointer variable.
 Here the terms enclosed with in angular bracket are
optional. And data type and * symbol with variable
are mandatory
Syntax:
<storage_class_specifier> <Type_Qualifier>
<Type_modifier> data type * pointer variable name ;
Example:
int *a;
Pointer Declaration

Syntax:
data type * pointer variable = &normal
variable name;
Example:
int *p;
int x=20;
p = &x;
Pointer Initialization
variable value address
p 9000 6000
x 20 9000

Example program:
#include<stdio.h>
#include<conio.h>
Void main()
{
int *p , x=15 ;
p=&x;
clrscr();
printf(“the value of x is %d”, x); 15
printf(“the address of x is %u“, &x); 4000
printf(“the value of pointer is %d”, *p); 15
printf(“the address of p is %u”, &p); 4002
getch();
} L.NIVETHA AP/CSE,KNCET

Referencing operator
The reference to an object can be created
using referencing operator ( & )
It is a unary operator and it appear before the
operand.
The operands of referencing operator should
be arithmetic type.
POINTER OPERATOR

Dereferencing operator:
The object referenced by a pointer can be
indirectly accessed by dereferencing the
pointer.
A pointer can be dereferenced by using a
dereference operator ( * ),
It is a unary operator it is appear before
the dereferenced operand

Example – 2
#include<stdio.h>
void main()
{
int a=10;
int *b=&a;
printf ( "%dn“ , a);
printf ( "%un“ , &a);
printf( "%dn“ , *b);
printf( "%un“ , &b);
}
10
6487580
10 output
6487568
--------------------------------
Process exited after 0.05086 seconds with return value 8
Press any key to continue . . .

The pointer are used for pointing different
data types.
if a pointer points any data types and is
known as void pointer.
Syntax:
void *pointer variable name ;
Example:
void *a;
float x=10.0;
a = &x;
Void pointer or generic pointer

1.Null pointer
A null pointer is a special pointer does not
points anywhere.
it does not hold address of any variable ,it is
assigned by 0.
Syntax:
datatype *ptr=0;
Example:
int *a ,*b;
a=b=0;
Accessing variable through pointer

Here we using pointer variable to do any arithmetic
operation through pointer expression.
Example:
#include <stdio.h>
void main()
{
int * a ;
int * b;
int x=10 , y = 20;
a=&x;
b=&y;
printf(“%d ” , (*a+*b));
printf(“%d” , (*a - *b));
}
Pointer expression

If a pointer variable holds the address of
another pointer variable , then that pointer
variable is said to be pointer to pointer variable
Syntax:
data type **pointer to pointer variable;
Example:
int *b;
int x=10;
int **a;
b=&x;
a=&b ;
Pointer to pointer

#include<stdio.h>
#include<conio.h>
Void main()
{
int a=10;
int *b;
int **c;
b=&a;
c=&b;
printf(“the value of a is %d”, a); 10
printf(“the value of b is %d”, *b); 10
printf(“the value of c is %d”, **c); 10
printf(“the address of a is %u”, &a); 1000
printf(“the address of b is %u”, &b); 2000
printf(“the address of c is %u”, &c); 3000
}

• Arithmetic operation also possible by using
pointer variable , it is mostly performed in
restricted form.
• Addition process : *a + *b
• Subtraction process : *a - *b
• Increment process : ++ptr
• Decrement process : --ptr
Pointer Arithmetic

Addition process :
In pointer possible add two pointer values
Here we add two pointers by using ‘+’
operator .
Here we access the pointer variable by
using dereference operator ‘ *’
Example:
int *a ,*b;
int x=10 , y=20;
a=&x , b=&y;
printf(“%d” , (*a + *b));

Subtraction process :
In pointer possible to subtract two pointer
values
Here we subtract two pointers by using ‘
- ’ operator .
Here we access the pointer variable value
by using dereference operator ‘ *’
Example:
int *a ,*b;
int x=10 , y=20;
a=&x , b=&y ;
printf( “%d” , (*a - *b));

#include<stdio.h>
#include<conio.h>
Void main()
{
int *a , *b , x=10, y=20;
a=&x;
b=&y;
printf( “Addition :%d”, *a + *b);
printf( “Subtraction: %d”, *a - *b);
printf( “Multiplication: %d”, *a * *b);
getch() ;
}

• Increment and decrement operation only
performed on pointer address,
• Here output of the increment and decrement
operation is performed based on the data
type declared .
Effect of increment & increment
operator

Example program:
#include<stdio.h>
#include<conio.h>
Void main()
{
int *p , x ;
p=&x;
Clrscr();
printf(“%u”, &x); 2000
printf(“%u”, ++p); 2002
printf(“%u”, --p); 2000
printf(“%u”, p++); 2002
printf(“%u”, p--); 2000
getch();
}

It is possible to create a pointer that points to a
complete array instead of pointing to the individual
element of an array. Such a pointer is known as a
pointer to an array.
Syntax:
Datatype * array pointer variable [size] ;
Example:
Int *ptr[10]
Int x=10 , y=20;
Ptr[0]=&x
Ptr[1]=&y
Arrays of pointer

#include<stdio.h>
#include<conio.h>
Void main()
{
int a[5]={10,20,12,13,14}, c;
int *p[5]; a[5]
clrscr();
for(i=o ; i<5 ; i++)
{
p[i]= &a[i];
printf( “ %u”, p);
printf( “%d”, *p);
getch();
}
2000 10
2002 20
2004 12
2006 13
2008 14

Selection sort
0 1 2 3 4 index
A={ 1 , 3 , 5, 6 , 10}
<
5<3 T temp =
Temp=A[0]
A[0]=A[3]
A[3]=temp

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