table of Contents
First, the process of parallel and concurrent
Parallel: Parallel refers both to perform, such as race, two people are kept ahead of him; (enough resources, such as three threads, quad-core CPU)
Concurrency: Concurrent refers to a limited resources, both alternately turns using resources, such as a road (monocytes CPU resources) while only one person had, after a period of A to go, give B, B continue to run A, used interchangeably, it aims to improve the efficiency.
Second, the difference between parallel and concurrent
Parallel is microscopically, i.e. at a precise moment of time, in different program execution, which requires the existence of a plurality of processors.
Concurrency is from the macro, in a period of time can be seen to be performed simultaneously, such as a server process multiple session.