Ploymorphism

Ploymorphism
the word Ploymorphism is a combination of two words poly and morphism. poly means
many and morphism means form. In object oriented programming Ploymorphism is the ability
of objects of different types of respond to functions of the same name. The user does not have to know the exact type of the object in advance. The behavior of the object
can be implemented by using virtual functions. A pointer can also refer to an object of a class. The member of an object can be accessed through pointers by using the symbols. The symbols
is known as member access operator. An array can store same types of data and an array of pointer is
also can be stored memory addresses of the object of same clases user to . It allows the user to
create a large number of objects in memory .

Pointers and inheritance
Pointers have very important capability of storing the addresses of different objects
A pointer can be store the address of object whose type is same as the type of pointer
. It can be be also store the address of any object that belongs to any child class of the class of pointer. Suppose there are three classes A,B and also C.The class A is a parent class wheres B and C
are child classes. A pointer of class A can store the addresses all objects of A as well as B and C.

The Type of pointer does not change when a pointer of parent class refers to an object
of child class. That is why, the pointer always execute the member functions of parent class
even if refers to a child object in the memory.

Virtual Functions
It means existing effects but not in realty. A type of function is that appears to exist in some part
of a program but does not exist really is called Virtual function. It Also used to important
functions.

Early Binding
 The assignment of types to variables and expression at compilition time is known as
Early binding. It is also called static binding. The early binding occurs
when everything required to call a function is known at compile time. Early binding enables the computer know exactly witch function will be called when a certain statement is executed.

When a program is compiled, the compiler checks the functions calls and decides which function is
to be executed. This process takes place during compilation process in normal programs with functions.

Read More

Arrays

Arrays
An array is a group of consecutive memory locations with same name and type. Simple
variable is a single memory location with a unique name and a type. But an array is a collection of different adjacent memory locations. all these memory locations have one collective
name and type. the memory locations in the array are known as elements of array. The total number
of elements in the array is called its length.
Each elements in the array is accessed with references to its positions of location in the array. This
positions is called index or subscript.Each elements in the array has a unique index. The index
of first element is  0 and the index of last is element length is -1. The Value
the index written in brackets along with the name of array.
Arrays are used to store a large amount of similar kind of data. Suppose the user wants
to store the marks of 100 students and declares 100 variables. It is time consuming process to
use the these variables individually. This process can be simplified by using array. An array is
of 100 elements can be declared to store these values instead of 100 individual variables.

Array initializations
The process of assigning values to array elements at the time of array declaration is called
array initialization. This process provides a list of initial values of array elements. The value
are separated with commas and enclosed within braces. there must be at least one initial
value between braces. A syntax errors occurs if the value in braces are more than length of array
. So if the number of initial values is less than the array sizes the remaining array elements
are initialized to zero.

Declaring one dimensional arrays
A type of array in which all elements are arranged in the form of list is known as
on dimensional array. It is also called single dimensional array or linear list. It consists
of one column or one row. The process of specifying array name length and data type is called
array declaration.

Read More

Loops

A type of control structure that repeats a statements is known as looping structure. It is also known as iterative or repetitive structure. In sequential structure all statements are executed once.on the other hand Conditional structure may execute or skip a statement on the basis of some given condition.In some situations it is required to repeat s statement or number of statements For a Special number
of Times. Looping Structures are used for this purpose. There are different types of loops available in
C++.

Counter Controlled Loops 
This type of loop depends on the value of a variable known as counter variable. The value
of counter variable is incremented or decremented each time the body of the loop is executed
. So This Loop terminates when the value of counter variable reaches a particular value. The
Number of iterations of counter controlled loop is in advance.The iteration of this loop depends on the terminating condition,increment or decrement value.

Sentinel Controlled Loops
This type of loop depends on special value known as sentinel value. The Loop terminates
when the sentinel value is encountered. These Types of loops are also known as conditional
loops. A Loop may execute while the value of a variable is not here. The Number of iteration
of sentinel controlled loop is unknown. It depends on the input from the users. Suppose the
 sentinel value to terminates a loop is 1 if the users enter 1 in first iteration,the loop will
execute only once. But if the user enter after entering many other values,the number of iterations
will very accordingly. A sentinel value is commonly used with while and Do-while loop.

While Loop
This is the simplest loop of C++ language. This Loop executes one or more statements while the
given condition remains true. It is useful when the number of iterations is  not known in advance.First of All the condition is evaluated. If it is true,the control enters the body of the loop and executes
all statements in the body. After executing the statements it again moves to the start of the loop
and evaluates the condition again. This process continues as long as the condition remains true.
When the condition becomes false/the conditions remains true,the loop never ends. A loop that
has not end points is known as an infinite loop.

Read More

Mapping

Mapping is a process of converting one level to another level. In this process,the data
at one level is related to the data and another level.

The conceptual/internal mapping defines the correspondence between the conceptual view and
stored database. It specifies how conceptual records and fields are represented at the internal level
if the structure of stored database is changed, then the conceptual mapping must be changed
accordingly so that the conceptual schema can remain consistent. It is the responsibility
of DBA to manage such change.

Read More

Logical , Internal Or Physical level

Logical or conceptual Level
This is the middle level view in three level architecture. The logical or conceptual
level describes the data stored in database. It contains the definition of the data to be stored 
in the database. It also contains the rules and information about the structure and type of 
data. It is the complete description of data stored in database. That is why it is also known as a community view of the database.This level contains the logical structure of entire database as seen. It hides the details of physical storage instruction physical Storage  structure

The conceptual level supports each external view. It means that any data require by
any user must be available from conceptual view. The conceptual model is comparatively 
constant. Dba designs a conceptual mode to fulfill the present and future requirements of
the organization. If there is any charge in external model, The conceptual model should 
be able to accomodate that change. It is important because any changes in the conceptual 
models requires a lot of effort. It also effects other views or levels of the database. the conceptual level is described in conceptual schema. There is only one schema for one database.

Internal Or Physical level

Internal level is responsible to store data on storage media. It describe the physical 
representation of database on computer. It describes how the data is stored in database . It 
covers the data structures and file organization used to store data on storage devices.
Internal and physical levels are normally considered to be same. But there is a slight method 
is implemented by operating systems. DBMS partially decides the way data is stored on the Disk. The binary storage This decisions is based in the specifications of DBA. Additionally 
DBMS adds information to the data to be stored For example it selects a specific files 
organization for storing data on the disk. It also applies different data encryption
algorithms to implement security on the data.

It performs a storage space utilization to consume minimum space for storing data 
The data compressions can be performed for this purpose. It also applies 
different data encryption algorithms to implement security on the data.

The records at internal level are presented according to the format of schema difinition
but the data is not in the record format at physical level. It is in character format. The rules 
specified by the schema of record are not enforced at physical level. Data is managed 
by operating system at physical level.

Read More

three level architecture and external level

 Three level architecture
Database Task group developed and published a proposal for a standard vocabulary
and architecture for database system in 1971. It was appointed by a conference
on database system and Languages. The Standards Planning and requirement
committee of American National standards institute committee on information processing
developed and published a similar vocabulary and architecture in 1975.

The result of these reports was the three level architecture. The three level architecture
is the basic of modern database architecture. Database can be viewed at three levels. The three
levels are depicted by three models known as three level schema. The models refers to the structure
of the database not the data stored on it. The parmanent structure of database is known as
intension of database or schema. The data stored at a given time is known as extension of database
or database instance.

The Intension of a database should not be changed once it has been defined. This is because a small
change in the intension of database may requires many changes to the data stored in database
. The extension of database is performed according to the rules defined in the intension of database.

The schema is used to store definition of the structure of the database. It can be any thing
like a single intity or the whole organization. Three level architecture define different
schemes are stored to the different levels to isolate the details of different levels from
one another.
external level
The external level consists of different external views of a database. Each external
view is the view of a particular user about the system. Different users conceive
the system in the different ways. Each users  is interested in one part of the system and
ignores other parts. One user may not be aware of the whole system at all.

Different views may have different representations of the same data. For example,one
user may think that dates are stored in form. Another user may think they are represented
as year/month/day.

Some views might include virtual or calculated data. Virtual data is the data that is not actually
stored in database but created when needed. For Example, the product name and its
price can be used to stored in database. The total bill can be created as and when desired
 so Similarly can be calculated when result card is prepared.

Read More

The internet

The internet is a collection of Milions computers around the World That are all connected to one another.It is
a global network of computers.These Computers are connected through different telecommunications links
like Phone Lines ,Fiber optic Lines, Satellites and wireless connections
internet is used to find information stored on computer called hosts or sevens.These
computers use a common protocol Called TCP/IP for communication.TCP/IP stands
for transmission Control Protocol/Internet Protocol.

No government or organization is the owner of internet. Many people,organizations,universities
and research agencies participate to run Internet.Everyone who has access to the Internet can get
information from the Internet.Millions of people have access to Internet.

Working of Internet
The network is used by the Computers to communicate with cable Modem.These devices
Communicate with the server of Internet Server Provider.
A user computer is usually connected with ISP using phone lines,DSL or cable Modem
 The computers connected to the Internet exchange data and information using servers
and clients.A client computer accesses data,information and services from different
servers.The server computer are also called host computers.

Positive aspects of Internet in society

The positive effects of the Internet of the society are as follows:
internet has converted this world into a global village.people are connected with one another
using the internet with one another using internet.It has provided more opportunities
of interaction.It also enables people to understand the views of one another.
Internet contains information on all types of topics.people can search information on any topic any Article.Search engine is used to search information on Internet .Easy access to
information has enabled people to be informed.
The uses of internet has provided many comforts for society.People can perform their Duties
easily.

Negative aspects of Internet in Society
Internet contains a large numbers of websites.These websites contains such material
that is against the moral values of our society.
Internet is the the most important source of spreading computer viruses.People spread viruses
using Internet and Emails.many websites also contain different viruses that are copied
to the computers when the users visits to These websites.And it is also The wastage of time because a many young waste their time on Chatting.

Read More