《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 https://github.com/codists/English-In-CS-Books 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：https://www.etymonline.com

(2) Cambridge Dictionary：https://dictionary.cambridge.org

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