Comprehensive theory, key formulas, diagrams, and memory aids for Cloud Computing.
Cloud computing is the delivery of computing services such as servers, storage, databases, networking, software, and analytics over the Internet, commonly referred to as "the cloud". Instead of owning and maintaining physical computers and servers, individuals and organisations rent computing power and storage from cloud providers and pay only for what they use. This model has completely transformed the way businesses operate, making powerful computing available to everyone, from a small startup to a multinational corporation.
The National Institute of Standards and Technology (NIST) defines cloud computing as a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released with minimal management effort. The cloud is built on the concept of virtualisation, where physical servers are divided into multiple virtual machines that can run independently. Users access these resources through a browser or an application, without worrying about the underlying hardware.
In this chapter we will study the characteristics and benefits of cloud computing, its service models such as IaaS, PaaS, and SaaS, its deployment models such as public, private, hybrid, and community clouds, and its advantages and disadvantages. We will also look at real-world examples of cloud services like Google Drive, Microsoft Azure, and Amazon Web Services. This chapter connects networking, web services, and databases into a complete picture of modern IT infrastructure.
Cloud computing has several essential characteristics that distinguish it from traditional computing.
These five characteristics, defined by NIST, are the essence of the cloud model and are frequently tested in examinations.
Cloud services are offered in three main service models, depending on the level of control the user needs.
IaaS provides the fundamental computing resources such as virtual machines, storage, and networking over the Internet. The user has control over the operating system, storage, and deployed applications, but not over the underlying physical infrastructure. Examples include Amazon EC2, Microsoft Azure Virtual Machines, and Google Compute Engine. IaaS gives the maximum control to the user.
PaaS provides a platform where developers can build, test, and deploy applications without worrying about the underlying infrastructure. It includes the operating system, programming language execution environment, database, and web server, all managed by the provider. Examples include Google App Engine, Microsoft Azure App Services, and Heroku. PaaS is ideal for developers who want to focus only on writing code.
SaaS delivers complete software applications over the Internet on a subscription basis. The user does not manage the application, operating system, or hardware; they simply use the software through a browser. Examples include Google Drive, Google Docs, Microsoft Office 365, and Gmail. SaaS is the most common cloud model used by everyday users.
Based on who owns and controls the cloud, deployment models are classified as follows.
The choice of deployment model depends on cost, security, and regulatory requirements.
Virtualisation is the technology that makes cloud computing possible. It is the process of creating a virtual version of physical resources such as servers, storage, or networks. A physical server can be divided into several virtual machines (VMs), each with its own operating system, running independently on the same hardware. The software that manages this division is called a hypervisor.
Virtualisation offers many benefits: better utilisation of hardware, lower costs, easier management, faster provisioning, and isolation between tenants. Because of virtualisation, cloud providers can pool their physical resources and serve thousands of customers from a single data centre. Virtualisation and cloud computing together form the backbone of modern data centres.
Some well-known cloud service providers and products include:
Cloud computing powers streaming services like Netflix, online gaming, mobile apps, and AI services, proving its importance in every field.
| Service Model | Full Form | What is Provided | Example |
|---|---|---|---|
| IaaS | Infrastructure as a Service | Virtual machines, storage, network | Amazon EC2 |
| PaaS | Platform as a Service | Platform for building apps | Google App Engine |
| SaaS | Software as a Service | Ready-to-use software | Google Drive |
| Deployment Model | Ownership | Best For |
|---|---|---|
| Public Cloud | Third-party provider | Cost-effective general use |
| Private Cloud | Single organisation | High security and control |
| Hybrid Cloud | Public + Private | Balance of cost and security |
| Community Cloud | Several organisations | Shared common interests |
graph TD
A["Cloud Computing"] --> B["Characteristics"]
A --> C["Service Models"]
A --> D["Deployment Models"]
A --> E["Virtualisation"]
A --> F["Advantages"]
A --> G["Disadvantages"]
B --> B1["On-demand, Broad access"]
B --> B2["Pooling, Elasticity, Measured"]
C --> C1["IaaS - Infrastructure"]
C --> C2["PaaS - Platform"]
C --> C3["SaaS - Software"]
D --> D1["Public, Private"]
D --> D2["Hybrid, Community"]
E --> E1["Virtual machines, hypervisor"]
F --> F1["Cost, scalability, accessibility"]
G --> G1["Internet needed, security, lock-in"]
Cloud computing has revolutionised how computing resources are delivered and consumed. In this chapter we learned that the cloud provides on-demand, scalable, and measured access to computing resources over the Internet. We studied the three service models, IaaS, PaaS, and SaaS, and the four deployment models, public, private, hybrid, and community clouds. Virtualisation, the enabling technology behind the cloud, allows physical resources to be shared efficiently. While cloud computing offers cost savings, scalability, and accessibility, it also brings challenges of security, vendor lock-in, and Internet dependence. Understanding the cloud prepares students for the modern world of AI services, web development, and data science.