Virtual machine is a collection of software like JVM (java virtual m/c) that provides run time environment (e.g. data structure support) to user applications. Such software is now referred with the terms virtualization that is running two or more copies of the same operating system or two or more different operating systems and virtual servers. The host software, which provides this capability, is often referred to as a virtual machine monitor or hypervisor. It resides between the hardware and the "guest" operating systems.
There are four major conceptual models of Virtual Machines used today and cater for different problem The IBM Model as demonstrated in the IBM S/390 solved the need for a single computer system that could simulate multiple computers with different operating systems.
instruction set and maps JVM calls to operating system calls. It simulates a fake CPU that interprets the fake CPU instructions (what is usually referred to as byte code). The most significant feature of the Java Virtual Machine the ability write a program once and execute it with Java Virtual Machines on multiple platforms. The OSI Virtual Machine and the Unix Virtual Machine, represented by the Unix user shell are used to create operating systems and providing services and functions at the operating system level that did not exist in the system hardware.
The OSI Virtual Machine model solved the problem of providing services and functions at ...
The OSI Virtual Machine model solved the problem of providing services and functions at the operating system level that did not exist in the system hardware. The Unix Virtual Machine model solved series of computer engineering problems by addressing the need for a modular approach to managing the launching and control of Unix processes. The success of the Unix operating systems is to a largely to the versatility and scalability of the Unix process.
The History of Virtual Machines
Around 1965 the researchers at IBM Yorktown Research center, developed first virtual machine environment, for the IBM System/360 mainframe called VM, which was entirely based in software. Later, IBM developed an implementation of its notion of a virtual machine and added hardware circuits to provide more robust and speedy partitioning between system images. This real world operating system, allows the user to share the resources available on their mainframe computers with many people, thus creating a multiple user environments. . This machine is now known as the IBM System 370 (S/370) and the IBM System 390 (S/390). These machines make use of the IBM VM/ESA operating system and are collectively referred to as IBM's VM lineage.
Virtual Machine Research Paper 4
Benefits of running a virtual machine
Virtual machine allow user to write applications on one OS and it can be executed on a machine which runs a different OS.One use is to provide multiple users the illusion of having an entire computer. Another advantage is that booting and restarting a virtual machine can be much faster than with a physical machine, since it may be possible to skip tasks such as hardware initialization.
Virtual machine allows for testing OS's and requires less