《Operating System Concepts》學(xué)習(xí)第 3 天，p9-p12 總結(jié)，總計(jì) 4 頁。

一、技術(shù)總結(jié)

1.interrupt

interrupt具有優(yōu)先級(priority)。

2.storage

指令只能在 memory 上執(zhí)行，所以要執(zhí)行程序，那么就要加載到內(nèi)存上。

(1)RAM

General-purpose computers run most of their programs from rewritable memory, called main memory (also called random-access memory, or RAM). Main memory commonly is implemented in a semiconductor technology called dynamic random-access memory (DRAM)。

main memory也稱為 RAM， primary memory， 關(guān)于 memory 的術(shù)語非常多，每次看到就頭疼，需要根據(jù)上下文去理解具體指的是什么，這里記一下。

(2)ROM

Instead, for this and some other purposes, the computer uses electrically erasable programmable read-only memory (EEPROM) and other forms of firmware—storage that is infrequently written to and is nonvolatile.

二、英語總結(jié)(生詞：3)

1.maskable

(1)mask: masque("a covering for hidding or guarding the face")

(2)maskable: mask + -able("capable of being")

adj. capable of being masked(hidden or blocked)，可屏蔽的。

(3) nonmaskable: non- + maskable

示例：Most CPUs have two interrupt request lines. One is the nonmaskable interrupt, which is reserved for events such as unrecoverable memory errors. The second interrupt line is maskable: it can be turned off by the CPU before the execution of critical instruction sequences that must not be interrupted(《Operating System Concepts》第 10 頁)。

2.preempt

(1)preemption: pre-("before") + emption(*em-, "to take, to buy")

也寫作 pre-emption。c/u. Preemption originally means "a purchase by one before an opportunity is offered to others(有限購買權(quán))"， which later evolved to mean "the act of preventing sth from happening by taking action first(優(yōu)先采取行動預(yù)防某事發(fā)生，即先發(fā)制人) "

(2)preempt: back-formation of pre-emption.

也寫作pre-empt。vt. to prevent sth from happening by taking action first, to take action before others（搶占，先占）。

示例：The interrupt mechanism also implements a system of interrupt priority levels. These levels enable the CPU to defer the handling of low-priority interrupts without masking all interrupts and makes it possible for a high-priority interrupt to preempt the execution of a low-priority interrupt(《Operating System Concepts》第 11 頁)。

3.volatile

(1)volatile: volare("to fly")

adj. fly away or disappeare quickly. likely to change suddenly and unexpectedly, especially by getting worse(不穩(wěn)定的)。否定形式是 nonvolatile。

示例：Since RAM is volatile—it loses its content when power is turned off or otherwise lost—we cannot trust it to hold the bootstrap program(《Operating System Concepts》第 11 頁)。

這里用 volatile 形容 RAM，是想表示當(dāng)電腦斷電的時候，RAM上的數(shù)據(jù)會丟失。

關(guān)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

1.英語句子中的省略

在技術(shù)書籍中，偶爾會遇到為了簡潔性省略句子結(jié)構(gòu)(如：賓語(object))的情況，此時要搞懂被省略的內(nèi)容是什么，才能更好的理解整個句子。

示例：We need an efficient way to dispatch to the proper interrupt handler for a device(《Operating System Concepts》第 9 頁)。

在這句話中，dispatch 是及物動詞 ，但是后面卻沒有賓語(object)，被省略的詞是 interrupts，實(shí)際應(yīng)該是We need an efficient way to dispatch interrupts to the proper interrupt handler for a device。

2.名詞(noun) vs 動名詞(gerund)

在閱讀過程中，經(jīng)常會遇到有時候使用的時候單詞的名詞形式，但是有時候表示的名詞意思，但是用的動名詞(gerund)形式。

示例：A common way to solve this problem is to use interrupt chaining, in which each element in the interrupt vector points to the head of a list of interrupt handlers(《Operating System Concepts》第 10 頁)。

在這里，chain 本身也可以做名詞，c. a series of things of the same type. 但這里使用的是動名詞形式 chaning, chaning 強(qiáng)調(diào)了這是一個 process 或者一種 machenism——interrupt chaning refers to the method of linking multiple interrupt handlers, and emphasizes how interrupts are handled dynamically.

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

歡迎搜索及關(guān)注：編程人(a_codists)