The concept and characteristics of process

Concept of Process

In the case of multi-channel programs, multiple programs are allowed to execute concurrently, and they will be blocked and have the characteristics of continuity and non-reproducibility. For this reason, the concept of Process is introduced to better describe and master the concurrent execution of programs, and to complete the concurrency and sharing of fragmented operations.

In order for a program involved in concurrent execution (including data) to function autonomously, it must be equipped with a special data structure called a Process Control Block (PCB). PCB is applied piecemeal to depict the fundamental state of the process and the operating form, and then to master and manage the process. Responsively, the process image (process entity) is composed of program segment, coherent data segment and PCB. The so-called creation process is essentially the PCB in the creation process image; and the revocation process is essentially the PCB of the revocation process. It is worth noting that process images are static and processes are static.

Note: PCB is the only sign of process existence!

From a different perspective, the process can have different definitions, more typical definitions are:

A process is an implementation of a procedure.

A process is the movement that occurs when a program and its data are executed sequentially on a processor.

A process is a process in which a self-contained program runs on a collection of data. It is a self-contained unit that implements capital allocation and adjustment.

After introducing the concept of process entity, we can define the process in the traditional operation system as: "Process is the operation process of process entity, and it is an independent unit that stops capital allocation and adjustment." "

process characteristics

Process is derived from the concurrent execution of multiple programs, and it and program are two identical concepts. The fundamental characteristic of the process is that it is presented against the order of performance of individual procedures and is also a fundamental request for process governance.

Static: Process is a procedure to perform, it has the creation, movement, pause, termination and other processes, has a certain life cycle, is static occurrence, change and death. Staticness is the most fundamental characteristic of a process.

Concurrency: refers to multiple process entities, stored in memory, can run at the same time in a period of time, concurrency is the main feature of the process, but also the main feature of the operation fragmentation. The goal of introducing a process is to enable it to perform concurrently with other processes to improve capital utilization.

Independence: refers to the process entity is a self-functioning, self-access to capital and self-adjustment of the basic unit. Any program that does not have a PCB cannot operate as an independent unit.

Asynchronous: Because of the mutual restriction of the process, the process has the continuity of performance, that is, the process is pushed forward at an independent and unpredictable speed. Asynchronous will lead to non-reproducibility of performance results, for this reason, in the operation of the system must be equipped with a response to the process synchronization mechanism.

Constructivity: Each process is equipped with a PCB to describe its stop. Structurally, the process entity consists of program segment, data segment and process control segment.