Introduction to virtual machines (ix) -- Summary of virtual machines

Virtual Machine Summary

The basis of all four virtual machine models is to combine commands to simulate devices or machines.

The Virtual Machine project aims to introduce the advantages and Applications of virtual machines to interested readers. First, we define the four Virtual Machine Conceptual models currently in use. They are the IBM models used on ibm s/390; java Virtual Machine Models Used in cross-platform Internet applications and extended virtual machine models used in modern operating systems. Finally, we introduced the UNIX Virtual Machine Model, which is presented in the form of a UNIX User Shell. The basis of all four virtual machine models is to combine commands to simulate devices or machines. Each type of virtual machine has its main characteristics, which solve completely different problems faced by computer and software engineers.

A single computer system can use an IBM model to simulate multiple computers with different operating systems. This allows you to create and manage multiple virtual machine copies on a computer. A major feature of the IBM model is that programs share the same hardware by dividing computer resources and fully isolated programs.

The Java Virtual Machine meets the needs of applications running on multiple operating systems. The cross-platform portability provided by Java Virtual Machine eliminates the need for programmers to rewrite programs to port programs to other types of operating systems. The main feature of a Java virtual machine is that a program can be executed on multiple platforms by relying on the Java Virtual Machine once it is written.

The OSI virtual machine model solves the problem of providing services and functions that do not exist in the system hardware at the operating system level. The extended virtual machine creates more complex instruction sets by combining commands to provide virtual devices or services to the user layer. The main advantage of extended machines is to use software to establish virtual devices and expand computer system features. The basic commonality of the three virtual machine concepts is that user-level commands are mapped to lower-level commands and then returned to the user level. These action flows are transparent to users. But do not confuse the words "Transparent" and "virtual. A transparent object actually exists, but the user cannot see it. In comparison, a virtual object can be seen by users, but it does not actually exist.

The UNIX Virtual Machine Model manages the loading and control of UNIX processes through modular methods, which solves a series of computer engineering problems. The success of UNIX is largely due to the versatility and testability of UNIX processes.

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