It is the most hot topic in the IT industry currently.Your program is divided into many parts. The part that you interact with (UI) is stored in your computer but the part that does essential processing is stored in servers somewhere else. UI in turn interacts with part(s) on server. The part(s) stored somewhere else (servers) form(s) a cloud because you don't worry about how the processing is being implemented on the sever. You have to only worry about your essential data being passed and stored in the servers if those servers belong to someone else (Companies).What you are using right now is on cloud.

Imagine you need to share a lot of videos on a website and with limited storing capacity you share some videos on other server in your network. Which may be at geographically different location but is in your network.(Search Google for VPNs).The user when watches the videos is not aware of the fact that the video he is watching the video is present coming from a server which is in a geographically different location than where the website is.

You may be authenticated to use a website but you may not be authorized to change the content which a website admin can do. So security is the headache to some extent how the application has been developed.

Now take a different scenario,
You can see a practical example railways website. You have a server running which is serving millions of transactions per second .If one of the server becomes busy then the transaction should not fail the application should be intelligent enough to communicate on another server which is free i.e. can handle that request and perform same changes to databases which has been requested at booking counter. If you do not have a cloud of servers running you will not be able to do it fastly.

Security is responsibility of system administrators and developers who developed that system.Well very simply put, cloud computing is all about getting a software service over network and more importantly internet.There is nothing new in cloud computing as a concept, because email, web, and many other services have been available over the internet/network for many years now.

What is happening now, is

1. Internet is getting faster.
2. Computing demands of individuals are rising.
3. Consumer software keeps on getting outdated.

The paradigm shift that cloud computing provides is that an ordinary user can have an inexpensive laptop/slate computer and run applications on cloud. Using Google docs vs ms office is a typical example.

The landscape of getting services delivered over internet is huge and possibilities are innumerate. And it is one of the modern buzzword. Also there are all sorts of systems, networking, hardware and security challenges in providing cloud computing. So you find almost every company doing something or else doing with the cloud.

Lastly cloud computing has sort of become a buzz word like "dot com" used to be about 10 years back. People must understand that cloud computing is nothing new from a technology point of view. But it is a shift in how we perceive software services.

Not everything can be done over cloud and even with the advent of cloud computing traditional will still continue. What industry experts claim is that we will see a shrinking desktop market and desktops will be replaced by more mobile computers like notebooks, net books, smart phones , slate computers and smart devices like smart cam coders etc. This will be backed by increasing sizes of data centers all over the world.

Characteristics of cloud computing

Agility – On demand computing infrastructure

Reliability and fault tolerance

Self healing – Hot backups, etc

SLA driven – Policies on how quickly requests are processed

Multi-tenancy

Service-oriented

Virtualized

cost-effective

platform, location and device independency

Basically an Internet-based network is made up of large numbers of servers Contain vast amounts of information. Users only care about the service or information, not about the underlying details.

History of Cloud computing

In 1960 It was found by John McCarthy and  came into commercial use around the turn of the 21st century .By, 2007 saw increased activity, including Google, IBM .It was a hot topic by mid-2008 and numerous cloud computing events had been scheduled.

Computer

Computer have made great in roads in everyday in our life and thinking. They are put to use for all sorts of application ranging from complex calculations in the field or frontline research, engineering simulations down to teaching, printing books and recreational games. The ease with which computers can process data, store and retrieve it painlessly has made them inevitable in office and business environments. The areas of application of computers are confined only by limitations on human creativity and imagination. In fact any task that can be carried out systematically can be performed by a computer. Therefore, it is essential for every educated person today to know about a computer, its strength, its weakness and its internal structure.

Computer- Computer is an electronic device that can perform a variety of operations in accordance with a set of instructions called program. Computer can access and process data millions of time faster than human can. A computer can store data and information in its memory, process them and produce the desired results. Computers can do a lot of different tasks such as playing games, railway reservation, weather forecasting, error detection and controlling the flight of space aircrafts etc.

A computer is used essentially as a data processor. The term data and information are very commonly used. We must understand clearly between the two.

Data: Data in computer terminology means raw facts and figures. For example ‘Mohan’, 1977, ‘A’, -162.19, + 75.2 are data.

Information: It means what e=we get after processing data (meaningful data). Data are aggregated and summarized in various meaningful ways to form information. For example ‘Mohan, whose roll number is 1977, has got grade A’ is an information as it is conveying some meaning.

Functioning of computer- Before we know the functioning of computer, let us understand the way we function. To understand this, let see some examples.

(i)Consider a case when your mother asks you to bring a cake and pastries from market. You go to market, purchase both the things and give it to your mother.

(ii)You want to talk to one of your friends. His phone number is 9042564846. So you dial up the number and speak to your friend.

(iii)Your mom has to make tea. So she takes some things (ingredients) i.e. ¾ cup of water, ½ teaspoon tealeaves, ½ teaspoon sugar and ½ cup of milk. She makes the tea by following certain steps like boiling water, adding tealeaves, sugar and milk. Finally you get prepared tea.

Above examples illustrate the way human being function. Consider all the three examples. There are certain things common in them. In all the examples certain things were needed to work upon, the actual work was then carried accordingly and finally the result was obtained.

Following table explains it

INPUT, PROCESS AND OUTPUT

All the above examples undergo three stages. The first stage (things to work upon) is called input stage. The second stage (the actual work being performed) is called process stage and third stage (the result) is called output stage. Certain input is necessary to accomplish a task; a process is carried out on the input to obtain the output.

Every task follows this input-process-output (IPO cycle in short). A computer is not exception to this rule. A computer also follows the I-P-O cycle i.e. it needs certain inputs, carries out a process and produces the output.

FUNCTIONAL COMPONENTS OF A COMPUTER

Since a computer follows input-output-process cycle the first stage is performed in computer in computer by input unit, second stage is performed by output unit. Thus the basic unit of a computer is as shown in below figure.

INPUT UNIT------------------------------CENTRAL PROCESSIG UNIT (CPU) ---------------------------OUTPUT UNIT

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MAIN MEMORY

(BASIC STRUCTURE OF COMPUTER)

The main memory holds the input and intermediate output during the processing.

INPUT UNIT- The input unit is formed by the input devices attached to the computer. Examples of input devices and media are: keyboard, mouse, magnetic ink character reader (MICR), optical mark reader (OMR), optical character reader (OCR), joystick etc.

The input unit is responsible for taking input and converting it in to computer understandable form (the binary code). Since a computer operates on electricity, it can understand only the language of electricity i.e. either ON or OFF or high voltage or low voltage. That means a computer can understand two stages ON/OFF or HIGH/LOW voltage or the binary language that uses just two symbols: 1 for ON and 0 for OFF.

An input unit takes the input and converts it in to binary form so that it can understand by the computer.

Consider the input of three earlier examples. All the inputs consisted of data (on which the action is to performed) as well as the instruction (the action to be taken)

INPUT COMPRISED OF DATA AND INSTRUCTION

On the same line, the computer input also consists of data and instruction. For example, if the given input to the computer is Add 2 and 3 and instruction is Add. Similarly, if the given input ‘Manisha’ then the data consists of ‘Manisha’ and instruction is print.

CENTRAL-PROCESSING UNIT -The CPU is the control centre for a computer. It guides, directs and governs its performance. It is the brain of the computer. The CPU has two components which are responsible for different functions. These two components are its control unit (CU) and arithmetic logic unit (ALU).

Arithmetic logic unit (ALU) - The ALU performs all the four arithmetical (+, -, *, /) and some logical (, +, =, ) operations. When two numbers are required to be added, these numbers are sent from memory to ALU where addition takes place and the result is put back in the memory. The same way other arithmetic operations are performed.

For logical operations also, the numbers to be compared are sent from memory to ALU where the comparison takes place and the result is returned to the memory. The result of a logical operation is either FALSE or TRUE. These operations provide the capability of decision –making to the computer.

Control unit (CU) – The CU controls and guides the interpretation, flow and manipulation of all data and information. The CU sends control signal until the required operations are done properly by the ALU and memory. Another important function of CU is the program execution i.e. carrying out all the instruction stored in the computer. The CU gets program instructions from memory and executes them one after the other. After getting the instructions from memory in CU, the instruction is decoded and interpreted i.e. which operation is to be performed. Then they asked operation is carried out. After the work of this instruction is completed, control unit sends signal to memory to send the next instruction sequence to CU.

The control unit even controls the flow of data from input devices to memory and from memory to output devices.

OUTPUT UNIT

The output unit is performed by the out devices attached to the computer. The output coming from the CPU is in the form of electronic binary signals which needs conversion in some form of electronic binary signals which needs conversion in some form which can be easily understand by human beings i.e. characters, graphical or audio visual. This function of conversion is performed by output signal is performed by output units. Some popular output devices are VDU (Visual display unit), printer, plotter, speech synthesizer and coder etc.

THE MEMORY

Well, if a computer has a brain (CPU), it must have a faculty which we call memory. Indeed, it does posses a memory, however, the memory of a computer is most unlike human memory. A human being can remember stored information for a long period whereas a computer cannot. Its memory is temporary (volatile), it cannot remember anything after it gets switched off.

The memory of a computer is more like a predefined working place, where it’s temporarily keeps information and data facilitate its performance. When the task is performed, it clears its memory and memory space is then available for the next task to be performed. When the power is switched off, everything stored in the memory gets erased and cannot be recalled.

The memory of a computer is often called as main memory or primary memory. It is generally the third component of CPU. The memory of a computer can be thought of as cells. The memory cell may also be defined as a device which can store a symbol selected from the set of symbols.

Each of these cells is further broken down in to smaller parts known as bits. A bit means a binary digit i.e., either 0 or 1. A number of bits are used to store data instructions by their combination.

SAN in an acronym for Storage Area Network. It is can be linked the server of a remote storage device in such a way that the device appears to be attached to the user’s system locally. SANs often use the Fiber Channel fabric topology, which is an infrastructure designed to manage storage communications. It also provides quick and reliable access than other higher-level protocols. A Fiber Channel SAN fabric is made up of a various Fiber Channel switches. Almost every major SAN equipment vendor offers a Fiber Channel routing solution that brings satisfying and quantifiable benefits to the SAN architecture. This sends data across different fabrics without merging them. Despite the fall in prices, SANs are still mostly uncommon outside larger enterprises.

Computer Evolution 
The concept of computer did not materialize overnight. Just as the growth and development of mature biological species normally took place in fits and started over the ages, the computer also took thousands of years to mature.
Ancient’s people used stones for counting or made scratches on a wall or tied knots in a rope to record information. But all these were manual computing techniques. Attempts had been going on for developing faster computing device used by man. Let us take a look at the development of the computer through various stages.
ABACUS
About 3000 years before the birth of Jesus Christ, the Mesopotamians quite unknowingly laid the foundation of the computer era. They discovered the earliest form of a bead-and-wire counting machine, which subsequently came to be known as abacus. The Chinese improved upon the abacus so that they could and calculate fast.
An abacus consists of beads divided in to two parts which are movable on the rods of the two parts. Addition and multiplication etc. of numbers is done by using the place value of the digits of the numbers and position of beads in the abacus.
NAPIER’S ‘LODS’ AND ‘BONES’
John Napier (1550-1617) developed the idea of logarithm. He used ‘logs’ to transform multiplication problem to addition problem. Napier’s logs later became the basis for a well known invention-the computing machine known as ‘slide rule’ (invented in 1662). Napier also devised set of numbering rodes known as ‘Napier Bones’. He could perform both multiplication and division with these bones.
The idea of logarithm, developed in 1614, notably reduced the tedium of repetitive calculations.
PASCAL’S ADDING MACHINE
Blaise Pascal, a French mathematician, invented a machine in 1642 made up of gears which was used for adding numbers quickly. This machine was named as Adding machine and was capable of addition and subtraction. It worked on clockwork mechanism principle. The adding machine consisted of numbered toothed wheels having unique position values. The rotation of wheels controlled the addition and subtraction operations. This machine was capable of carry-transfer automatically.
LEIBNITZ’S CALCULATOR
Gottfried Leibnitz, a mathematician, improved an adding machine and constructed a new machine in 1671 that was able to perform multiplication and division as well. This machine performed multiplication through repeated addition of numbers. Leibnitz’s machine used stepped cylinder each with nine teeth of varying lengths instead of wheels as was used by Pascal.
JACQUARD LOOM
Joseph Jacquard manufactured punched cards at the end of American Revolution and used to them to control looms in 1801. Thus the entire control weaving process was automatic. The entire operation was under a program’s control. With the historic invention of punched cards, the era of storing and retrieving information started that generally influenced the later inventions and advancements.
BABBAGE’S DIFFERENCE ENGINE
Charles Babbage, a professor of mathematics, developed a machine called Difference Engine in the year 1822. This machine was expected to calculate logarithmic tables to a high degree of precision. The difference engine was made to calculate various mathematical functions. The machine was capable of polynomial evaluation by finite difference and its operation was automatic multistep operation.
BABBAGE’S ANALYTICAL ENGINE
In 1833, Charles Babbage started designing an Analytical Engine which was to become a real ancestor of the modern day computer. With the methodical design of his Analytical Engine, Babbage meticulously established the basic principles on which today’s computer work. The Analytical engine was capable of performing all the four arithmetic operations as well as comparison. It had a number of features startlingly similar to those in today’s electronic computers. He included the concept of central processor, storage area, memory and input-output devices in his design. The two revolutionary innovations incorporated in Analytical Engine were comparisons and modification of stored information. The first innovation enabled the machine to compare quantities and then decide which of the instruction sequences to follow. The second permitted the results of a calculation to change numbers and instruction already stored in the machine. Owing to the lack technology of the time, the Analytical Engine was never built. Its design remained conceptual.
His great inventions of difference engine and analytical engine earned Charles Babbage the title ‘Father of modern computers’ – a fitting tribute to him.
HOLLERITH’S MACHINE
In 1887, an American named Herman Hollerith (1869-1926) fabricated what was dreamt of by Charles Babbage. He fabricated the first electromechanical punched-card tabulator that used punched cards for input, output and instructions. This machine was used by American Department of census to compile their 1880 census data and was able to complete compilation in 3 years which earlier used to take around 10 years.
MARK-I
Prof. Howard Aiken (1900-1973) in U.S.A. constructed in 1943 an electromechanical computer named Mark-I which could multiply two 10 – digit number in 5 seconds – a record at that time. Mark – I was the first machine which could perform according to pre programmed instructions automatically without any manual interference. This was the first operational general purpose computer.