《Operating System Concepts》學習第 44 天，p495-p511 總結，總計 17 頁。

一、技術總結

1.cache

(1)定義

A cache is a region of fast memory that holds copies of data.

(2)cache 和 buffer 的區別

The difference between a buffer and a cache is that a buffer may hold the only existing copy of a data item, whereas a cache, by definition, holds a copy on faster storage of an item that resides elsewhere.

2.spool

(1)定義

A buffer that holds output for a device (such as a printer) that cannot accept interleaved data streams.

二、英語總結(生詞：2)

1.urgency

(1)urge: urgere("press hard, push forward")

vt. try strongly to persuade sb to do sth.

(2)urgent

adj. very important and needing attention immediately(緊急的)。

(3)urgency: urgent + -cy

u. the quality of being very important and needing attention immediately(緊急性，緊迫性)。

(4)示例

We need multilevel interrupts, so that the operating system can distinguish between high- and low-priority interrupts and can respond with the appropriate degree of urgency when there are multiple concurrent interrupts(《Operating System Concepts》第 495 頁)。

2.reserve

(1)reserve: re-("back") + servare("to keep")

vt. to keep back for further use。

(2)示例

Most CPUs have two interrupt request lines. One is the nonmaskable interrupt, which is reserved for events such as unrecoverable memory errors(《Operating System Concepts》第 496 頁)。

(3)reserve vs preserve

reserve: to save sth for later use。

preserve: maintain sth in its original manner/state。

關于英語的注解同步更新匯總到 https://github.com/codists/English-In-CS-Books 倉庫。

三、其它

今天沒有什么想說的。

四、參考資料

1. 編程

(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/

2. 英語

(1) Etymology Dictionary：https://www.etymonline.com

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

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