출처
https://velog.io/@ssh1997/CS-Process-%ED%94%84%EB%A1%9C%EC%84%B8%EC%8A%A4
https://velog.io/@raejoonee/%ED%94%84%EB%A1%9C%EC%84%B8%EC%8A%A4%EC%99%80-%EC%8A%A4%EB%A0%88%EB%93%9C%EC%9D%98-%EC%B0%A8%EC%9D%B4
https://jogendras.wordpress.com/2014/09/26/program-vs-process-vs-thread-vs-task/