Virtual machine summary
All the four virtual machine models are combined instructions to go to analog devices or machines.
The main purpose of the virtual machine project is to introduce the advantages and applications of the virtual machine to be interested in readers. We first concentrate on the four virtual machine concept models that are currently use, they are: IBM models used on IBM S / 390; Java virtual machine models used in cross-platform Internet applications; and in modern operations Extended virtual machine model used in the system. Finally, we introduced the UNIX virtual machine model, which is manifested in the form of a UNIX user's shell. All the four virtual machine models are combined instructions to go to analog devices or machines. Each type of virtual machine has its main feature, which solves completely different problems faced by computer and software engineers.
A single computer system can simulate multiple computers with different operating systems via the IBM model. This allows users to create and manage multiple different virtual machine copies on a computer. One of the main features of the IBM model is to share the same hardware by splitting computer resources and complete isolation programs.
The Java virtual machine meets the needs of the program running on multiple operating systems. The cross-platform portability provided by the Java virtual machine allows the programmer to override the program without rewriting the program to other types of operating systems. The most important feature of the Java virtual machine is that the program can only be written once to execute the Java virtual machine on multiple platforms.
The problem with the OSI virtual machine model is: Providing system hardware does not exist in service and functionality at the operating system level. Extended virtual machines create a more complex instruction set by combining instructions to provide virtual devices or services to the user layer. The main advantage of expansion machines is to use software to establish virtual equipment and extend computer system characteristics. The basic common common common common work of the three virtual machines is that the user-level directive is mapped to the lower layer instruction, and then returns to the user level. These action processes are transparent to the user. But don't confuse both words "transparency" and "virtual". A transparent object is actually existing, but the user can't see it. 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 modular methods, which solves a series of computer engineering issues. The success of UNIX is largely derived from the versatility and measurableness of the UNIX process.
The powerful and successful virtual machine concept is that the user can access and utilize the functions and devices that can be formed only by the combination of instruction sets. The ability to provide a virtual solution for the real restriction of modern computer systems is a powerful tool that will continue to extend the capacity of modern computer systems.
