1.What is the life cycle of a process？

A process is a dynamic entity, the entire life cycle of a process from creation to extinction.Processes can go through a variety of states, generally three.

（1）Ready state: the process has acquired all resources except the CPU and is waiting in the ready queue for the CPU to dispatch it；

（2）Execution status: the CPU has been obtained and all required resources are running；

（3）Blocking state (wait state) : the process abandons the processor because it is waiting for the required resource, or the process does not own the processor in the first place and other resources are not satisfied.

2.Why does the process have to have a PCB？

PCB is a part of process entities and are the most important recorded data structures in the operating system.It can make a program that cannot run independently in a multi-program environment become a basic unit that can run independently and become a process that can execute concurrently with other processes.