OSI virtual machine model
"Virtual" is implied to somewhere, although an object or device does not exist, people can see it
The word "virtual machine" is easy to make many people have a rich association. Popular media and news broadcasts are often used in the "virtual" word when reporting new development of computer simulation and computer games. In either case, using "virtual" is hintting somewhere, although an object or device does not exist, people can see it. Virtual use is a reasonable hypothesis about expanding the development of virtual machines. The creation of the extension virtual machine is to increase the two logic of computer operating systems on capabilities and flexibility.
To understand how the extension virtual machine model is to understand how modern computers are designed and how the operating system controls it. The modern operating system consists of a series of instruction sets, and the instruction set combines to form a service routine. The service routines and data are combined together to become an application submitted to the computer. Combine the instruction into a service routine, so that the office staff combines simple movements to complete a more complex task (such as office supply directory). For example, a clerk has only one limited instruction set that can be performed in memory. These instructions are limited to calculations, record the results of the previous operation, and archive some information to prepare. Use these instructions alone, there is not much value, but these instructions can be combined into a sequence that makes the clerk completed an office supply directory. This instruction sequence may be: the number of recorded paper, record results, number of pencils, record results, number of paper clamps, recording results, archive save. This sequence can be repeated to complete the directory service request. The instructions such as "Number of Record Paper" are assumed that the office clerk has instincts like identifying recorded paper and precise counting. For humans, identify objects and counts are natural features of clerk brain and eyes. For simulated office clerks or computers, these features need to be designed in the hardware level and reflected in the circuitry. When examining the operation of the office clerk, it is clear that some of the basic functions that are frequently used in the circuitry are required, rather than a combination of simple instructions. The office clerk must personally walk in the office, check the object, use notepad and pencil recording count results, and so on. These features will be implemented as a series of repetitive hardware actions and software instructions. For example, "Record the last result" This instruction will include the following: Access a storage component (such as a disk memory), locating the storage data space, get the data to be recorded in the local register, transfer data, and writing data hard disk. At the circuit layer, there is a basic layer, all instructions are derived from this level.
The bottom of the underlying directive is a zero code submitted to the computer. They generate mobile data, configure the system, or create a condition for the next action. This level can be considered to be a machine command level, and the operating system level instruction is derived from this level. Now, we all clearly know that any instruction set is a simple combination of its next layer instruction set. The task of the office clerk is actually a series of subtasks. These subtasks are combined together to form a more complex operation sequence. When the "Directory" command is issued to the office clerk, the observer can only know the meaning of the word of this word and the overall action of the office clerk. The underlying instruction subset is invisible to the observer. Each consecutive instruction layer, including machine circuitry, machine code, operating system instruction, and application code, all of which hide its underlying instructions. Combine instructions and build more complex operations are the key to understanding the expansion of the virtual machine.
