The 'Cloud Computing' technology refers to

Correct — C, (c) A distributed computer architecture that provides software, infrastructure and platforms just as required by applications/users.

THE KEYED OPTION IS A DEFINITION IN DISGUISE, AND IT NAMES ALL THREE SERVICE MODELS. Read it slowly: 'software, infrastructure and platforms' is the standard trio of what a cloud sells, and 'just as required' is the on-demand property that makes it a cloud rather than merely a data centre.

SOFTWARE AS A SERVICE — a finished application delivered over the network, used through a browser. Web mail, an online document editor, an online accounting package. The customer manages nothing but their own data and settings. PLATFORM AS A SERVICE — an environment on which the customer's own programs run: a runtime, a database, deployment tooling. The customer writes the application; the provider looks after everything under it. INFRASTRUCTURE AS A SERVICE — raw computing capacity: virtual machines, storage, networking. The customer installs the operating system and everything above it.

The three form a ladder of how much the customer manages, from nearly nothing to nearly everything.

THE FIVE PROPERTIES THAT MAKE SOMETHING A CLOUD, as the standard definition sets them out:

ON-DEMAND SELF-SERVICE — capacity is taken when needed, without asking a human. BROAD NETWORK ACCESS — reached over a network from ordinary devices. RESOURCE POOLING — one pool of physical machines serves many customers, each isolated from the others. RAPID ELASTICITY — capacity grows and shrinks quickly, and appears unlimited to the user. MEASURED SERVICE — usage is metered and billed for what is consumed.

WHAT MAKES IT WORK IS VIRTUALISATION: software that carves one physical machine into several independent virtual ones, so that capacity can be handed out, moved and reclaimed in minutes instead of weeks.

AND WHY ORGANISATIONS MOVE TO IT. Buying servers means paying in advance for the busiest hour of the year and owning idle metal for the rest of it. A cloud converts that capital expenditure into an operating expense, removes the sizing guess, and shortens the wait for new capacity from months to minutes. The costs are real too — dependence on a provider, questions about where data physically reside and under whose law, and the fact that a network failure is now a service failure. In India the government's own effort in this direction is the GI Cloud initiative, MeghRaj, which offers common cloud infrastructure to departments rather than leaving each to build its own.

The stem prints 'Cloud Computing' in single quotation marks with both words capitalised, and option (c) prints 'applications/users' with a solidus and no spaces, as set.

Why the others are wrong

• (a)A set of algorithms that solves problems using fuzzy logic — A real branch of computing, and entirely unrelated. FUZZY LOGIC is a form of many-valued logic in which a statement need not be simply true or false but can hold to a DEGREE between 0 and 1, so that a temperature can be 'somewhat hot' rather than being forced into hot or not-hot. It was set out by Lotfi Zadeh in 1965 and is used in control systems where a smooth response matters more than a sharp threshold — the load sensing in a washing machine, the compressor control in an air conditioner, anti-lock braking, autofocus in cameras. It belongs to the artificial-intelligence family alongside neural networks and expert systems. Nothing about it concerns how computing capacity is delivered or paid for, which is the entire subject of cloud computing. The option is here as a category error rather than a near miss.
• (b)Many computers that are interconnected through wireless networks and satellites — The closest of the three, and worth separating carefully, because a cloud IS built from many interconnected computers. What is wrong is that this describes a NETWORK, and stops there. A cloud is defined not by its wiring but by what it does with it: pooling the machines so that many customers share them invisibly, provisioning capacity on demand without human intervention, expanding and contracting it in minutes, and metering the usage. The physical links are also mis-described — a cloud data centre is built on high-capacity optical fibre, and satellite links, being slow to traverse and expensive per unit of data, are the last thing such an architecture rests on. Compare the option with the keyed one: option (c) names the same interconnection as a 'distributed computer architecture' and then adds what that architecture DELIVERS, which is precisely the half that is missing here.
• (d)A futuristic technology that will use clouds to perform computing — A literal reading of the name, and the name is a metaphor. The cloud in 'cloud computing' comes from the drawing convention in network diagrams, where the network you do not need to see inside is sketched as a cloud; the term simply means that the machinery is somewhere on the other side of the network and its details are not the user's concern. No meteorological cloud is involved. The word 'futuristic' is the second error: cloud services were ordinary commercial infrastructure well before this paper was set, running public web services, government systems and business applications at scale. It is a useful habit to be suspicious of any option that describes a working technology as something that 'will' exist, since the exam is asking what a term means today, not what a science-fiction reading of its name might suggest.

CLOUD COMPUTING is the delivery of computing resources — processing, storage, networking, software — as an on-demand service over a network, from a shared pool that the provider maintains, with the customer paying for what is used.

THE THREE SERVICE MODELS, distinguished by how much the customer manages:

IaaS, INFRASTRUCTURE AS A SERVICE — virtual machines, storage and networks. The customer installs the operating system and everything above it. PaaS, PLATFORM AS A SERVICE — a ready environment on which the customer runs their own applications, with the runtime, database and deployment tooling provided. SaaS, SOFTWARE AS A SERVICE — a complete application delivered over the network and used through a browser.

THE FOUR DEPLOYMENT MODELS, distinguished by who may use the cloud:

PUBLIC — offered by a provider to any customer over the internet. PRIVATE — operated for a single organisation, whether on its own premises or hosted. COMMUNITY — shared by organisations with common requirements, such as a group of government departments. HYBRID — a combination, typically keeping sensitive work private while bursting into a public cloud for peaks.

THE FIVE ESSENTIAL CHARACTERISTICS in the standard definition are on-demand self-service, broad network access, resource pooling, rapid elasticity and measured service. A system that lacks these is a hosted data centre rather than a cloud.

THE ENABLING TECHNOLOGY IS VIRTUALISATION. A layer of software, the hypervisor, divides one physical server into several isolated virtual machines that can be created, moved and destroyed in minutes. That is what makes pooling and elasticity possible, and it is why the same physical hardware can serve unrelated customers safely.

NEIGHBOURING TERMS worth keeping distinct. DISTRIBUTED COMPUTING is the general idea of many machines co-operating on a task. GRID COMPUTING harnesses many independently administered machines for a large computation, typically scientific. EDGE COMPUTING pushes processing out to where data are generated, to cut delay and backhaul. VIRTUALISATION is the technique underneath cloud, not a synonym for it.

THE TRADE-OFFS. In favour: no capital outlay, no capacity guess, quick provisioning, professional operation and geographic redundancy. Against: dependence on one provider and the difficulty of leaving, questions of where data physically sit and which country's law applies to them, the need for a reliable network, and a security model in which responsibility is shared between provider and customer rather than resting wholly with either.

IN INDIA, the government's GI Cloud initiative, MeghRaj, provides common cloud infrastructure for departments so that each does not build its own, and public services increasingly run on such shared infrastructure.

Key facts

• Cloud computing delivers computing resources as an on-demand service over a network, from a shared pool, billed by usage.
• The three service models are Infrastructure as a Service, Platform as a Service and Software as a Service — a ladder of how much the customer manages.
• The four deployment models are public, private, community and hybrid.
• The five essential characteristics are on-demand self-service, broad network access, resource pooling, rapid elasticity and measured service.
• Virtualisation is the enabling technology: a hypervisor divides one physical server into several isolated virtual machines that can be created and reclaimed in minutes.
• The economic case is the conversion of capital expenditure into operating expenditure, with no need to buy for the busiest hour of the year.
• The main risks are dependence on a single provider, uncertainty about where data physically reside and under whose law, network dependence, and a shared security responsibility.
• The word 'cloud' comes from the drawing convention of sketching a network as a cloud in diagrams; nothing meteorological is involved.
• MeghRaj is the Government of India's GI Cloud initiative, providing common cloud infrastructure to government departments.
• Fuzzy logic — a many-valued logic in which truth is a degree between 0 and 1, set out by Lotfi Zadeh in 1965 — belongs to artificial intelligence and is unrelated to cloud computing.

Common traps

• Reading the metaphor literally. The cloud is a diagram convention for the network, not anything in the sky.
• Describing cloud computing as merely many interconnected computers. That is the network; the cloud is what is delivered over it.
• Confusing cloud computing with virtualisation, grid computing or distributed computing. Cloud uses the first and overlaps the others without being any of them.
• Mixing up the service models. Infrastructure gives machines, platform gives an environment for your code, software gives a finished application.
• Assuming a private cloud is not a cloud. The deployment model says who may use it, not whether it qualifies.
• Treating a technology that is already in commercial use as futuristic, which is what one option here invites.

• practice — not a real PYQ

  In cloud computing, the service model in which the provider supplies virtual machines, storage and networking while the customer installs the operating system and applications is called

  • (a)Software as a Service
  • (b)Platform as a Service
  • (c)Infrastructure as a Service
  • (d)Data as a Service

  Answer(c) Infrastructure as a Service — the provider supplies raw computing capacity and the customer manages everything above it. Software as a Service delivers a finished application, and Platform as a Service supplies a runtime environment on which the customer's own programs are deployed.

• practice — not a real PYQ

  'MeghRaj' refers to which one of the following ?

  • (a)India's national supercomputing mission
  • (b)The Government of India's cloud computing initiative
  • (c)A series of Indian weather satellites
  • (d)A national public Wi-Fi access programme

  Answer(b) The Government of India's cloud computing initiative — MeghRaj is the GI Cloud initiative, which provides common cloud infrastructure to government departments so that each need not build its own.