Introduction to Virtual Machines (ix)--Virtual Machine summary

Virtual Machine Summary



All four virtual machine models are based on a combination of instructions to simulate a device or machine.



The main purpose of a virtual machine project is to introduce the benefits and applications of virtual machines to interested readers. We first focused on defining the four virtual machine conceptual models that are being used today: the IBM model used on IBM s/390, the Java Virtual machine model used in Cross-platform Internet applications, and the extended virtual machine model used in modern operating systems. Finally, we introduce the UNIX virtual machine model, which is presented in the form of a UNIX user shell. All four virtual machine models are based on a combination of instructions to simulate a device or machine. Each type of virtual machine has its main characteristics, and these different characteristics address the completely different problems that computers and software engineers face.



A single computer system can simulate multiple computers with different operating systems through the IBM model. This allows users to create and manage multiple copies of different virtual machines on a single computer. One of the main features of the IBM model is to make programs share the same hardware by splitting computer resources and a complete quarantine program.



Java Virtual machines meet the need for programs to run on multiple operating systems. The Cross-platform portability provided by Java virtual machines allows programmers to rewrite programs without having to migrate programs to other types of operating systems. The main feature of the Java Virtual machine is that the program can be executed on multiple platforms on a Java virtual machine only once written.



The OSI virtual machine model solves the problem of providing services and features that do not exist on the system's hardware at the operating system level. The extended virtual machine provides virtual devices or services to the user layer by combining instructions to create more complex instruction sets. The main advantage of scaling machines is the use of software to build virtual devices and extend the characteristics of computer systems. The basic common denominator of three virtual machine concepts is to map user-level directives to lower-level directives and then back to user levels. These action processes are transparent to the user. But don't confuse the two words "Transparent" and "virtual". A transparent object actually exists, but it is not visible to the user. In contrast, a virtual object can be seen by the user, but it does not actually exist.



The UNIX virtual machine model manages the loading and control of UNIX processes through a modular approach, which solves a series of computer engineering problems. The success of UNIX is largely due to the versatility and scalability of the UNIX process.



The power and success of the concept of virtual machines is that users can access and exploit functions and devices that can be formed only through a combination of instruction sets. The ability to provide a virtual solution to the real limits of modern computer systems is a powerful tool that will continue to expand the capabilities of modern computer systems.