Operating-System-Concepts阅读笔记p272-p285
《Operating System Concepts》阅读笔记：p272-p285
《Operating System Concepts》学习第 27 天，p272-p285 总结，总计 14 页。
一、技术总结
1.semaphore
A semaphore S is an integer variable that, apart from initialization, is accessed only through two standard atomic operations: wait() and signal().
2.monitor
A high-level language synchronization construct that protects variables from race conditions.
3.liveness
A set of properties that a system must satisfy to ensure that processes make progress during their execution life cycle.
二、英语总结(生词：)
1.semophore
(1)semaphore: sema(“sign, signal”，参考 semantic) + phoros(“bearer”)
u. Semaphore literally means “mechanical apparatus for signaling to distant points(向远距离点发送信号的机械装置)”，refer to “a system of sending signals using visual cues(视觉线索)， such as flags(旗子) or lights(灯光)”。
(2)示例
A semaphore S is an integer variable that, apart from initialization, is accessed only through two standard atomic operations: wait() and signal()(《Operating System Concepts》第 272 页)。
2.indefinitely
(1)indefinite: in-(“not”) + definitus(“defined, set limite”，参考 definite)。
adj. not exact(不确定的), without clear limit(无限期的)。
(2)indefinitely: indefinite + -ly
adv. for a period of time with no fixed end(不确定地，无限期地)。
示例：A process waiting indefinitely under the circumstances just described is an example of a “liveness failure.”(《Operating System Concepts》第 283 页)。
3.inversion
(1)invert: in-(“in”) + vertere(“to turn”)
vt. to turn sth upside down(使颠倒)。
(2)inversion： act of inverting
(3) invert vs reverse
这两个词不好区分在于都包含 “opposite” 之意，目前我也没找到什么比较好的区分特征，先记录。
invert: turn upside down，turn inside out；flip。
示例1： the number 9 looks like an inverted 6
reverse: change in order, side, direction；reorder。
示例1：
Consider a list of two fractions: 1/2, 3/4.
If you invert the fractions: 2/1, 4/3.
If you reverse the fractions: 3/4, 1/2.
4.daunting
(1)daunt: dom-(“control”)
vt. to make sb feel sightly frightened or worried about their ability to achieve sth(使吓到，使气馁)。
(2)daunting:
adj. making sb feel slightly frightened or worried about their ability to achieve sth(令人发怵的，使人气馁的)。
(3)示例
Trying to identify when to use which tool, however, can be a daunting challenge (《Operating System Concepts》第 283 页)。
5.pessimistic
(1)pessimism: pessimus(“worst, very bad”)
u. the tendency to see the bad side of things(悲观主义，悲观情绪)。
(2)pessimist
c. a person who thinks that bad things are more likely to happen(悲观主义者)。
(3)pessimistic: pessimist + -ic。
adj. tending to think the worst aspect of things or believe that the worst will happen(悲观的).
(4)optimistically
optimistic(乐观的) 构词法同 pessimistic, 词根是 optimus，这里不再赘述。
关于英语的注解同步更新汇总到 仓库。
三、其它
今天没有什么想说的。
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：
(2) Cambridge Dictionary：
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