《Operating System Concepts》学习第 46 天，p512-p527 总结，总计 16 页。

一、技术总结

1.front-end processor

(1)定义

Small computers that perform certain tasks in an overall system; used by some systems to manage I/O and offload the general-purpose CPU.

(2)示例

terminal concentrator。

二、英语总结(生词：3)

1.malfunction

(1)malfunction: mal-("bad") + function

c/u. a situation in which a system stops working normally(故障)。

(2)示例

An operating system that uses protected memory can guard against many kinds of hardware and application errors, so that a complete system failure is not the usual result of each minor mechanical malfunction(《Operating System Concepts》第 511 页)。

2.transient

(1)transitent: trans-("across, beyond") + ire("to go")

adj. lasting for only a short time; temporary(短暂的，暂时性的)。Transient means literally "go across", which implies "pass through sth rather than staying"。

(2)示例

Devices and I/O transfers can fail in many ways, either for transient reasons, as when a network becomes overloaded, or for “permanent” reasons, as when a disk controller becomes defective(《Operating System Concepts》第 512 页)。

3.compensate

(1)compensate: com-("together, with") + pensare("weight, pay")

vt. give (sb) sth, like money, in recognition of loss, suffering or injure(补偿)。vi. to offset an error, defect, or undesired effect(弥补(错误，缺陷，不希望的结果))。

(2)示例

示例 1：His enthusiasm compensates for his lack of skil(他的热情弥补了他技术上的不足)。

在这个例子中，使用 “enthusiasm” 来弥补 “lack of skill”。

示例 2：Operating systems can often compensate effectively for transient failures. For instance, a disk read() failure results in a read() retry, and a network send() error results in a resend(), if the protocol so specifies(《Operating System Concepts》第 512 页)。

在这个例子中，如果只看第一句“通常，操作系统能有效弥补(应对)暂时性故障”，其实不大好理解，因为没有直接体现“使用什么来弥补什么”？翻译为“弥补”也不大通畅。需要结合后面一句来理解。operating system 是怎么弥补 transient failures 的呢？使用 “ read() retry” 来弥补 “read() failure”, 使用 “resend()” 来弥补 “send() error”。

从技术上来说不难理解，其实就是“重试机制”，但是如果不理解词的意思，有时候就不能很好的理解作者想表达的意思。

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 12 章(I/O Systems)简评：介绍 bus, controller, power management, STREAMS 等，也很抽象。

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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