Process and State Conversion

1. Basic Process status

(1) Execution status (running): Processes occupy the processor, ProcessesProgramExecuting. Only one process in a single-processor system is in the execution state, and multiple processes in a multi-processor system may be in the execution state.

(2) blocked: it is also called a waiting or sleep state. A process is in the paused State because it waits for an event. For example, a process waits for the completion of I/O and the buffer space.

(3) Ready: all necessary resources other than the processor have been allocated to the process and all the conditions for execution have been met. Multiple processes may be in a ready queue.

2. New status and termination status

(1) New State: the state in which the process has just been established and has not been sent to the ready queue.

(2) termination status: A process has ended normally or abnormally. The OS has removed it from the ready queue and has not undone it.

3.Process status
Conversion

A process can be in the ready and running status multiple times during execution, or blocked for multiple times, but only once in the new status.

(1) New state-> ready state: When the ready queue allows accepting new processes, the system will move the processes in the new State to the ready queue.

(2) ready state-> execution state: After the process scheduler assigns a processor to a ready process, the process enters the execution state.

(3) Execution state-> blocking state: the process being executed cannot be executed because it needs to wait for an event.

(4) blocking state-> readiness state: when an event waits for a process, the process enters the readiness state from the blocking state.

(5) Execution state-> readiness state: the process being executed is suspended because the time slice is used up. Or, after a process with a high priority arrives in the preemptible scheduling mode, A low-priority process being executed is forcibly removed from the processor and switched to the ready state.

(6) Execution state-> termination state: if a process is completed or a special event occurs, the process changes to termination state.