《Operating System Concepts》学习第 71 天，p808-p820 总结，总计 13 页。
一、技术总结
1.design principles of windows
(1)security
满足 C2 级别，基于 Discretionary Access Control(DAC)，attribute-based access control (ABAC)， claim-based access control (CABC)等。
二、英语总结(生词：2)
1.bounty
(1)bounty: bonus("good") + -ty
c. money paid as a reward(奖金，赏金)。
(2)示例
Additionally, bug bounty participation programs allow external researchers and security professionals to identify, and submit, previously unknown security issues in Windows(《Operating System Concepts》第 826 页)。
2.discretionary
(1)discern: dis-("apart, away") + cernere("distinguish, separate, sift",参考 *krei-"to seive(过滤，筛)", hence "distinguish")
vt. discern literally means to separate by distinguishing. to recognize sth that is not clear(辨别出)。
(2)discrete: dis-("apart, away") + cernere("distinguish, separate, sift",参考 *krei-"to seive(过滤，筛)", hence "distinguish")
adj. individually separate and distinct(独立的，各自的).
(3)discretion
u. the quality of behaving in such a way as to avoid causing offence(慎重)。
(4)discretionary: discretion + -ary
adj. available for use at the discretion of the user(可自行决定的，自主的)。
(5)示例
Windows traditionally based security on discretionary access controls. System objects, including files, registry keys, and kernel synchronization objects, are protected by access-control lists (ACLs) (see Section 13.4.2).(《Operating System Concepts》第 826 页)。
上面这句话的意思是：Windows 传统上将安全性建立在自主访问控制（Discretionary Access Control, DAC）基础上。系统对象（包括文件、注册表键和内核同步对象）都通过访问控制列表（ACLs）进行保护（参见第13.4.2节）。
关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。
三、其它
第 21 章(Windows 10)简评：分别从 History, Design Principles, System Components 等方面介绍 windows 系统，总体而言介绍很详细，介于实际开发中与 Windows 相关的内容并不多，所以选择快速过一遍即可。
完结，撒花，明天出读后感。
四、参考资料
1. 编程
(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/
2. 英语
(1) Etymology Dictionary：https://www.etymonline.com
(2) Cambridge Dictionary：https://dictionary.cambridge.org
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