Concurrency and parallelism

• Concurrency:    when there are multiple threads in action, if the system has only one CPU, it is impossible to actually make more than one thread at the same time, he can only divide the CPU run time into several time periods, and then assign the time period to each thread execution, when the thread code of a time period runs, Other threads are in a suspended state, which is called concurrency. • Parallel:    When one CPU executes a thread, another CPU can execute another thread, and two threads do not preempt CPU resources, which can be done concurrently, which is called parallelism.    concurrent execution of a program is a state in which two or more two programs are processed in the computer system and are not finished.

Concurrency and parallelism