Cloud computing delivers hosted services over the Internet and is broadly divided into three categories: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). IaaS provides virtual servers and storage, PaaS provides development tools on the provider's platform, and SaaS provides fully managed, front-end accessed applications. Cloud services are elastic, on-demand, and fully managed by the provider. Cloud computing builds on decades of research in virtualization and distributed computing to provide scalable, flexible computing resources and reduce IT costs for users.

1. Cloud computing is a general term for configure their virtual servers and storage.
anything that involves delivering hosted In the enterprise, cloud computing allows a
services over the Internet. These services are company to pay for only as much capacity
broadly divided into three categories: as is needed, and bring more online as soon
Infrastructure-as-a-Service (IaaS), Platform- as required. Because this pay-for-what-you-
as-a-Service (PaaS) and Software-as-a- use model resembles the way electricity,
Service (SaaS). The name cloud computing fuel and water are consumed, it's sometimes
was inspired by the cloud symbol that's referred to as utility computing.
often used to represent the Internet
inflowcharts and diagrams.
Platform-as-a-service in the cloud is defined
A cloud service has three distinct as a set of software and product
characteristics that differentiate it from development tools hosted on the provider's
traditional hosting. It is sold on demand, infrastructure. Developers create
typically by the minute or the hour; it is applications on the provider's platform over
elastic -- a user can have as much or as little the Internet. PaaS providers may use APIs,
of a service as they want at any given time; website portals or gateway software
and the service is fully managed by the installed on the customer's computer.
provider (the consumer needs nothing but a Force.com, (an outgrowth of
personal computer and Internet access). Salesforce.com) and GoogleApps are
Significant innovations in virtualization and examples of PaaS. Developers need to know
distributed computing, as well as improved that currently, there are not standards for
access to high-speed Internet and a weak interoperability or data portability in the
economy, have accelerated interest in cloud cloud. Some providers will not allow
computing software created by their customers to be
moved off the provider's platform.
A cloud can be private or public. A public
cloud sells services to anyone on the In the software-as-a-service cloud model,
Internet. (Currently, Amazon Web Services the vendor supplies the hardware
is the largest public cloud provider.) infrastructure, the software product and
A private cloud is a proprietary network or a interacts with the user through a front-end
data center that supplies hosted services to a portal. SaaS is a very broad market. Services
limited number of people. When a service can be anything from Web-based email to
provider uses public cloud resources to inventory control and database processing.
create their private cloud, the result is called Because the service provider hosts both the
a virtual private cloud. Private or public, the application and the data, the end user is free
goal of cloud computing is to provide easy, to use the service from anywhere.
scalable access to computing resources and
IT services.
Infrastructure-as-a-Service like Amazon
Web Services provides virtual
serverinstances with unique IP addresses
and blocks of storage on demand. Customers
use the provider's application program
interface (API) to start, stop, access and

2. business software. They cost less, because
you don’t need to pay for all the people,
products, and facilities to run them. And, it
turns out they’re more scalable, more secure,
What is cloud computing?
and more reliable than most apps. Plus,
upgrades are taken care of for you, so your
apps get security and performance
Life before cloud computing enhancements and new features—
Traditional business applications—like automatically.
those from SAP, Microsoft, and Oracle—
have always been too complicated and The way you pay for cloud-based apps is
expensive. They need a data center with also different. Forget about buying servers
office space, power, cooling, bandwidth, and software. When your apps run in the
networks, servers, and storage. A cloud, you don’t buy anything. It’s all rolled
complicated software stack. And a team of up into a predictable monthly subscription,
experts to install, configure, and run them. so you only pay for what you actually use.
They need development, testing, staging,
Finally, cloud apps don’t eat up your
production, and failover environments.
valuable IT resources, so your CFO will
When you multiply these headaches across love it. This lets you focus on deploying
dozens or hundreds of apps, it’s easy to see more apps, new projects, and innovation.
why the biggest companies with the best IT
The bottom line: Cloud computing is a
departments aren’t getting the apps they
simple idea, but it can have a huge impact
need. Small businesses don’t stand a chance.
on your business.
Cloud-computing: a better way
Cloud computing is a better way to run your
business. Instead of running your apps
yourself, they run on a shared data center.
When you use any app that runs in the
cloud, you just log in, customize it, and start
using it. That’s the power of cloud
computing.
Businesses are running all kinds of apps in
the cloud these days, like CRM, HR,
accounting, and custom-built apps. Cloud-
based apps can be up and running in a few
days, which is unheard of with traditional

3. Cloud computing builds on decades of research in virtualization, distributed computing, utility
computing, and more recently networking, web and software services. It implies a service
oriented architecture, reduced information technology overhead for the end-user, great
flexibility, reduced total cost of ownership, on-demand services and many other things.
The Cloud computing emerges as a new computing paradigm which aims to provide reliable,
customized and QoS guaranteed dynamic computing environments for end-users. In this paper, we
study the Cloud computing paradigm from various aspects, such as definitions, distinct features,
and enabling technologies. This paper brings an introductional review on the Cloud computing and
provides the state-of-the-art of Cloud computing technologies.