All computer system contain hardware components for data input , processing and out put . Computer mainly contain electronic components , namely transistors and ICs ( Integrated Circuits ) etc , and these components are connected with each other to form computer circuits . Software are stored programs which run on computer hardware to achieve desired result .  Computer can be classified according to thair .

A>> Application

B>> purpose

C>> size

A>>  Application :  

  Computers can be used to count number or to measure physical quantities . There can be three broad categories of computers as :

@  Digital computer

@  Analog computer

@  Hybrid computer  

~~>>  Digital computer : It operates on data which is in the form of bits ( binary digits ) . Input to digital computer is supplied in group of bits , called word . Group of bits represents numerals , latters or other special symbols as per the ASC|| ( American Standard Code For Information Interchange ) table . the input is discrete and a digital signal . Most of the present day computer are Digital Computer .

~~>>  Analog Computers :  These computers measures physical values such as temperature , pressure , flow of oil etc. These are Widely used in manufacturing units where temperatur , pressure , current , voltage etc are to be measured continuously . Example : An analog computer at a petrol pump can be used to measure the flow of petrol . Analog computers have many limitations such as :  

>>  These are not able to store large data .  

>>  Logical facilities available are quite limited .  

>>  Arithmetic operations have little accuracy .

~~>>  Hybrid Computers : Features of analog computers and digital computers are combined in Hybrid Computers . A hybrid computer used Analog - to - digital converter and Digital - to - analog converter . It accepts input in the form of continuously varying input , which is then converted into digital data ( discrete data ) and then process it to produce results . Conversion from analog data to digital data is done because digital signal processing is fast and more accurate . A hybrid computer is suitable in Real Time Applications . but they have very limited applications.

B>> Purpose :

According to thair purpose computer can be of two types :

1 >>  General Purpose Computer .

2 >>  Special Purpose Digital Computer .

1>> General Purpose Computer : It is a multi - purpose or all - purpose type of a computer . It can be used in larg variety of applications such as graphical , analytical , mathematical , commercial , web based etc. A personal computer ( P.C. ) is a general purpose digital computer .

2>> Special Perpose Digital Computer : It is designed to solve some specific problem . Example : A computer designed to count and check quality of fountain pens in a pen menuacturing industry

C>>  Size :

  Large system have greater processing speed , more storage capacity , high cost and they can handle large number of input and output devices . They can provide services to many user at the same time . Whereas the smaller system are used by single user ( one person at a time ) . According to thair size , computers can be broadly classified as :

@ >>  Micro Computers :

  These are low - end small size computers . Personal computer ( PCs ) and Laptop computer ( Notebook computer ) are in the category of micro - computers . These are low cost machines suitable for small business & scientific applications . A PC has less storage capacity , less processing power and less speed than mini - computer . A PC now - a - days has RAM of 512 MB , Hardisk of 80 GB capacity and CPU speed approximately 3.0 GHz .

@ >>  Mini computers :

  These are small general purpose computer system on which many user can work at the same time . These are more powerful and expensive than micro - computer system . About 4 to 32 user can work simultaneously on a mini - computer . Large number of peripheral devices , such as printers , plotters etc . can be connected to a mini computer . They are generally used in payroll preparation , scientific computations , graphical applications such as Geographical Information Systems ( GIS ) .

@ >>  Mainframe computers :

  These system have faster processing speed and greater capacity than mini - computers . These are expensive machnes and mainly used to solve complex problems . They are generally used in research organizations , large industrial houses , airline and railway booking network , insurance companies etc . They have the capability to execute computer programs written various computer language .

@ >>  Super computers :

  These are fastest and most expensive computer systems . They are multiprocessor systems and can handle large number complex problems at the same time . Theseare generally used in research organization , missile  development programs , aircraft designs, weather forecasting , remote sensing , space applications etc .CRAY - 1 , CRAY - 2 are the initial super computers developed in USA . India has also started manufacturing super computers and PARAM was the first Indian super computer developed by CDAC , pune .

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.