Shulou(Shulou.com)06/01 Report--

Process is the fundamental unit for the operation of piecemeal capital allocation and independent operation. It is generally composed of the following three parts.

Process control block

When the process is created, a new PCB construct is created in bits and pieces, which then resides in memory, can be accessed at any time, and deleted at the end of the process. PCB is a part of the process entity and the only mark of the process existence.

When creating a process, bits and pieces set up a PCB; for the process. When the process is performed, it PCB the current morphological information of the process, so as to stop mastering and managing it; when the process is finished, it sends out its PCB, and the process dies. Operation piecemeal through the PCB table to govern and master the process.

Table 2-1 what PCB includes on weekdays

Process description Information process Mastering and Governance Information Capital allocation list disposal Machine related Information process Identifier (PID) process Morphology Code Segment pointer Universal Storage value user Identifier (UID) process priority data Segment pointer address Store value

The code runs, the import address, the inn section pointer controls the value of the memory.

The program's out-of-memory address file descriptor marks the memory value

Enter the memory time keyboard shape word

Disposing machine occupies time mouse

Application of signal quantity

Table 2-1 is an example of PCB. PCB mainly contains process description information, process mastery and governance information, capital allocation list and disposal machine related information. The secondary clarifications of each part are as follows:

1) process description information

Process identifier: marks each process, each with a unique identification number.

User identifier: the user to which the process belongs, and the user identifier should serve for sharing and maintenance.

2) process mastery and governance information

Shape after the process: describe the morphological information of the process as the basis for the dispatch of the disposal machine.

Process priority: describe the priority of the process to preempt the processor, and the high-priority process can give priority to the processor.

3) Capital allocation list, which is used to clarify the situation about memory address space or virtual address space; the list of files opened and the output / input equipment information used.

4) the relevant information of the processor mainly refers to the values of each memory in the processor. When the process is switched, the morphological information of the processor must be kept in the response PCB, so that it can be performed continuously from the breakpoint when the process is re-performed.

In a piecemeal, there are many processes on weekdays, some in the proper form, some in the form of congestion, and the causes of congestion are different. In order to facilitate the adjustment and governance of the process, the PCB of each process needs to be organized in an appropriate way. At present, there are two commonly used organization methods: link method and index method. The linking method links the uniform PCB into a queue, and the divergent shape corresponds to the divergent queue, and the PCB in the process of congestion can also be arranged into multiple congestion queues according to the differences of the causes of congestion. The indexing method is to organize the unified process into an index table, the items of the index table point to the PCB of the response, and the bifurcation forms correspond to the divergent index tables, such as stop index table and choked index table.

Program segment

A program segment is a program code segment that can be transferred to CPU performance by the process adjustment program. Note that programs can be shared by multiple processes, which means that multiple processes can run a single program.

Data segment

The data segment of a process, so the original data processed and disposed of by the program corresponding to the process, or the final consequences that occur when the program is performed.

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