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Top 10 List of Week 01

1. Virtualization
   Virtualization is a technique of how to separate a service from the underlying physical delivery of that service. It is the process of creating a virtual version of something like computer hardware. With the help of Virtualization, multiple operating systems and applications can run on same machine and its same hardware at the same time, increasing the utilization and flexibility of hardware.
   

2. Types of Virtualization:
   

   Application Virtualization : helps a user to have a remote access of an application from a server.
   Network Virtualization : The ability to run multiple virtual networks with each has a separate control and data plan. Network virtualization provides a facility to create and provision virtual networks—logical switches, routers, firewalls, load balancer, Virtual Private Network (VPN), and workload security within days or even in weeks.
   Desktop Virtualization : It allows the user to access their desktop virtually, from any location by different machine.
   Storage Virtualization : an array of servers that are managed by a virtual storage system. It makes managing storage from multiple sources to be managed and utilized as a single repository.

3. Paging
   Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. This scheme permits the physical address space of a process to be non – contiguous. The mapping from virtual to physical address is done by the memory management unit (MMU) which is a hardware device and this mapping is known as paging technique.
   

4. Segmentation
   Segmentation is another non-contiguous memory allocation scheme like paging. In segmentation, CPU generates logical address that contains segment number and segment offset. If the segment offset is a smaller amount than the limit then the address called valid address, otherwise it throws miscalculation because the address is invalid.

5. Logical Address or Virtual Address
   Logical Address or Virtual Address is an address generated by the CPU. The set of all logical addresses generated by a program called logical address space or virtual address space. The logical address space is also splitted into fixed-size blocks, called pages:
   

   Page Number(p): Number of bits required to represent the pages in logical address space or page number.
   Page Offset(d): Number of bits required to represent particular word in a page or page size of logical address space or word number of a page or page offset.
   

6. Physical Address
   Physical address is an address actually available on memory unit. The set of all physical addresses corresponding to the logical addresses called physical address space. The physical address space is conceptually divided into a number of fixed-size blocks, called frames:
   

   Frame Number(f): Number of bits required to represent the frame of physical address space or frame number.
   Frame Offset(d): Number of bits required to represent particular word in a frame or frame size of physical address space or word number of a frame or frame offset.
   

7. Hypervisor
   A Hypervisor or VMM(virtual machine monitor) is a layer that exits between the operating system and hardware. It provides the necessary services and features for the smooth running of multiple operating systems. It identifies traps, responds to privileged CPU instructions and handles queuing, dispatching and returning the hardware requests.
   

8. Emulation
   Guest programs are executed within an environment that is controlled by the virtualization layer, which ultimately is a program. Also a completely different environment with respect to the host can be emulated, thus allowing the execution of guest programs requiring specific characteristics that are not present in the physical host.
   

9. Isolation
   Virtualization allows providing guests—whether they are operating systems, applications, or other entities—with a completely separate environment, in which they are executed. The guest program performs its activity by interacting with an abstraction layer, which provides access to the underlying resources.The virtual machine can filter the activity of the guest and prevent harmful operations against the host.
   

10. Cloud Computing
    Cloud Computing can be defined as the practice of using a network of remote servers hosted on the Internet to store, manage, and process data, rather than a local server or a personal computer. Types of cloud computing service:
    

    Software as a service (Saas) : a way of delivering services and applications over the Internet.
    Platform as a service (PaaS) : cloud computing that provides a platform and environment to allow developers to build applications and services over the internet.
    Infrastructure as a service (IaaS) : service model that delivers computer infrastructure on an outsourced basis to support various operations.