Cloud in Computer science

The Cloud is an umbrella term used for a whole bunch of things, most, but not all, having to do with getting software or computing resources delivered over the Internet as a service. These services are usually paid for on some kind of usage or subscription basis — a certain dollar amount per resource (like data) consumed, or per month. Stop paying, and service is cut off. This is different from buying a software product and getting to use it forever. Simply put, the cloud is the Internet—more specifically, it’s all of the things you can access remotely over the Internet. When something is in the cloud, it means it’s stored on Internet servers instead of your computer’s hard drive.

Some of the main reasons to use the cloud are convenience and reliability. For example, if you’ve ever used a web-based email service, such as Gmail or Yahoo! Mail, you’ve already used the cloud. All of the emails in a web-based service are stored on servers rather than on your computer’s hard drive. This means you can access your email from any computer with an Internet connection. It also means you’ll be able to recover your emails if something happens to your computer.

Cloud computing means storing and accessing data and programs over the Internet instead of your computer’s hard drive. It is the delivery of computing services—servers, storage, databases, networking, software, analytics and more—over the Internet (“the cloud”). 

Uses of cloud computing
If you use an online service to send email, edit documents, watch movies or TV, listen to music, play games or store pictures and other files, it is likely that cloud computing is making it all possible behind the scenes. Here are a few of the things you can do with the cloud:

• Create new apps and services
• Store, back up and recover data
• Host websites and blogs
• Stream audio and video
• Deliver software on demand
• Analyse data for patterns and make predictions

Types of cloud services: IaaS, PaaS, SaaS

Most cloud computing services fall into three broad categories: infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (Saas). These are sometimes called the cloud computing stack, because they build on top of one another.

1. Infrastructure-as-a-service (IaaS)
   The most basic category of cloud computing services. With IaaS, you rent IT infrastructure—servers and virtual machines (VMs), storage, networks, operating systems—from a cloud provider on a pay-as-you-go basis.
2. Platform as a service (PaaS)
   Platform-as-a-service (PaaS) refers to cloud computing services that supply an on-demand environment for developing, testing, delivering and managing software applications. PaaS is designed to make it easier for developers to quickly create web or mobile apps, without worrying about setting up or managing the underlying infrastructure of servers, storage, network and databases needed for development.
3. Software as a service (SaaS)
   Software-as-a-service (SaaS) is a method for delivering software applications over the Internet, on demand and typically on a subscription basis. With SaaS, cloud providers host and manage the software application and underlying infrastructure and handle any maintenance, like software upgrades and security patching. Users connect to the application over the Internet, usually with a web browser on their phone, tablet or PC.