出处：操作系统概述
文章参考：
《现代操作系统》第四版
https://baike.baidu.com/item/ 操作系统 / 192?fr=aladdin
《Modern Operating System》forth edition
http://faculty.cs.niu.edu/~hutchins/csci360/hchnotes/psw.htm
https://www.computerhope.com/jargon/c/clockcyc.htm
《B 站 - 操作系统》
https://www.bilibili.com/video/av9555596?from=search&seid=8107077283516919308
https://en.wikipedia.org/wiki/System_call
http://c.biancheng.net/cpp/html/238.html
http://www.dossier-andreas.net/software_architecture/layers.html
原文：https://www.cnblogs.com/myseries/p/12452412.html