Why we invent the concept of Process? Why   Process is divided into 5  not 6 or 4 states ? ( 引入进程概念的好处是什么？进程为什么划为5个状态？)

From a theoretical point of view it is an abstraction of the running program process; from an implementation point of view it is a data structure designed to clearly depict the inherent laws of the dynamic system and effectively manage and schedule access to the main memory of the computer system. It’s a program in execution and is the unit of work in a modern time-sharing system.

To require firmer control and more compartmentalization of the various programs because early computer systems allowed only one program to be executed at a time and this program had complete control of the system and had access to all the system’s resources.

Create (New): when the process is created you need to apply for a blank PCB to fill in the information for the control and management process and complete the allocation of resources.

Ready: the process is ready and has been allocated to the required resource. It can be run immediately as long as it is allocated to CPU

Running: the process is in order and the process enters the execution state after being scheduled

Waiting: the executing process is temporarily unable to run due to certain events the process is blocked and when a request is received a ready state is waiting for a system call.

Termination: the end of the process or an error or termination of the system into the termination state and unable to perform again.