Dynamic Objects,Pointer to function,Array & Pointer,Character String Processing

‘ Dynamic objects, pointer to function, array
and pointers, character string processing ’
Presented By:
Muskaan (MCA/25020/18)
Prashi Jain (MCA/25022/18)

DYNAMIC OBJECTS
C++ supports dynamic memory allocation and deallocation . C++
allocates memory and initializes the member variables.
An object can be created at run-time ; such an object is called a
dynamic object.
The new and delete operators are used to allocate and
deallocate memory to such objects.

NEW Operator
The new operator is used to allocate memory at runtime.
The memory is allocated in bytes.
Syntax:
DATA TYPE *ptr = new DATA TYPE;
// Pointer initialized with NULL
// Then request memory for the variable
int *p = NULL;
p = new int;
OR
// Combine declaration of pointer
// and their assignment
int *p = new int;

We can initialize a variable while dynamical allocation in the
following way:
int *ptr = new int (4);
Example:
#include<iostream.h>
#include<conio.h>
int main()
{
int *ptr = new int;
*ptr = 4;
cout << *ptr << endl ;
return 0;
}
OUTPUT: 4

DELETE Operator
A dynamic object can be distroyed by using the DELETE
operator
Syntax :
delete ptr;
Here ptr is the pointer to the dynamically allocated
variable
The delete operator simply returns the memory allocated
back to the operating system so that it can be used again.

Let’s look at an example:
int main()
{
int *ptr = new int;
*ptr = 4;
cout << *ptr << endl;
delete ptr;
return 0;
}
OUTPUT: 4

ADVANTAGES:
The main advantage of using dynamic memory allocation
is preventing the wastage of memory.
We can allocate (create) additional storage whenever we
need them.
We can de-allocate (free/delete) dynamic space whenever
we are done with them

POINTER TO FUNCTION
C++ allows you to pass a pointer to a function.
Simply declare the function parameter as a pointer type.
 Syntax:
data type fun_name(data type *arg)

Let’s look at an example:
#include <iostream.h>
void swap( int *a, int *b )
{
int t;
t = *a;
*a = *b;
*b = t;
}
int main()
{
int num1, num2;
cout << "Enter first number" << endl;
cin >> num1;
cout << "Enter second number" << endl;
cin >> num2;
swap( &num1, &num2);
cout << "First number = " << num1 << endl;
cout << "Second number = " << num2 << endl;
return 0;
}

OUTPUT:
Enter first number
2
Enter second number
4
First number = 4
Second number = 2

Array
An array is collection of items stored at
continues memory locations.
Syntax : Int arr[10]; //Array declaration by
specifying size

Pointers
A pointer is a variable whose value is the
address of another variable. Like any variable or
constant.
Syntax : type * var_name; //declaration of an
pointer
Example: int *p,a;
p=&a;

Arrays and pointers
Arrays and pointers are very closely related in c++.
For Example: An array declared as
Int a[10]
Can also be accessed using its pointers representation . The
name of the array is a constant pointer to the first element of the
array. So a can be considered as const int*.
Here arr points to the
first element of the array

For example:
In array and pointers ptr[i] and*(ptr+i) are considered as same.
Int a[4]={10,20,30,40};
Int *ptr = a;
for(int i =0 ; i<4; i++)
{
cout<< *(ptr+i) <<endl;
}
Output: 10
20
30
40

For the same array
For(int i=0 ; i<4;i++)
{
Cout<< ptr[i] <<endl;
}
Output:
10
20
30
40

Character string processing
String:
In C++, the one-dimensional array of characters
are called strings, which is terminated by a null
character 0.
Syntax: char greeting[6];

What is character string processing?
Character string processing basically means
accessing (insertion and extraction operators)
the characters from a string.
C++ provides following two types of string
representations −
• The C-style character string.
• The string class type introduced with Standard
C++.

Insertion operator : The result of inserting a char pointer to
an output stream is same as displaying a char array whose
first element is located at the address to which the char*
object points.
Example: Char text[9]= “world”;
For(char *ptr = text; *ptr!= ‘0’ ; ++ptr)
{ Cout<< ptr << endl;
}
Output : world
orld
rld
ld
d

Extraction operator
When the right operand of an extraction operator is a char*
object, the behaves same as extraction from char array- by
default leading white space is skipped and the next
nonwhitespace string of characters is extracted.
For example: char str[40];
Cout<<“enter a string:” ;
Cin>> str;
Cout<<“you entered :” <<str <<endl;
}
Output : enter a string : programming is fun
you entered: programming

String functions
1- strlen(): returns the length of the sytring.
Syntax: int strlen(s1);
2- strcpy(): copies one string to another string.
Syntax: char *strcpy(s1 , s2);
3- strcat(): this function concates two strings.
syntax: char *strcat(s1 , s2 );
4- strcmp(): compares two strings.
syntax: strcmp(s1 ,s2);

Dynamic Objects,Pointer to function,Array & Pointer,Character String Processing

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