Virtual-Globe

Yes before Going to see more about cloud computing , let us understand, how does it came into existence.....

Here are some clue, Cloud is nothing but clustering of clustering which contains many servers, each cluster is controlled by a controller may be software or hardware, and these Clusters are controlled and managed by an another Controller, like wise a system will be formed in an hierarchy.  So each Clusters have Servers, it can be Physical or Virtual...

you may ask what is this virtual...?

Answers for this question is not that simple to explain, you should take a look at what does it mean......

Virtualization: is virtualizing something that is physically existing. In computer science, Virtualization can do on Memory, Desktop, Hardware etc.
Using virtualization concept, people planned to build cloud computing in-terms of  SAAS, PASS and IAAS.
Virtualization enables to running multiple operating systems on the same computer, eliminating the need for extra computer, a saving in cost , reducing the footprint(i.e. disk space).

Running multiple Operating Systems is not a new concept. Early days Boot Manager, MAC OS  X Boot Camp which allows windows operating system to be installed on an Apple Machine. But more interesting and difference is that that today we are using soft-ware to install the operating system, it is simple and straightforward process.

Many advantages are there using Virtualization software, consider you want to run two operating systems and two server, in such case you can install everything in a single physical machine without requiring 4 different system for each operating systems and servers.  The physical machine OS is called as "HoSt", the Operating systems installed are called as "GuesTs".