《Operating System Concepts》学习第 33 天，p389-p407 总结，总计 19 页。

一、技术总结

1.virtual memeory

(1)定义

A technique that allows the execution of a process that is not completely in memory. Also, separation of computer memory address space from physical into logical, allowing easier programming and larger name space.

(2)实现方式

1）demand paging

demand--(on demand: when needed)。

2.page-replacement algorithm

In memory management, the algorithm that chooses which victim frame of physical memory will be replaced by a needed new (1)FIFO pagte replacement

(2)optimal page replacement

(3)LRU page replacement

二、英语总结(生词：3)

1.precaution

(1)caution: *keu-("to see, observe")

u. great care and attention(小心, 谨慎)。

(2)precaution: pre-("before") + caution

c. an action taken in advance to prevent sth unpleasant, dangerous or inconvinient from happening(预防措施)。

(3)示例

Dynamic linking can help to ease this restriction, but it generally requires special precautions and extra work by the programmer(《Operating System Concepts》第 390 页)。

2.confer

(1)confer: con-("together") + fere("to bear, carry")

vi/vt. to give sth(a title, degree, benefit or right)(给予)。

(2)示例

The ability to execute a program that is only partially in memory would confer many benefits(《Operating System Concepts》第 390 页)。

3.perceive

(1)perceive: per-("thoroughly, completely, entirely") + capere("to take, to grasp")

Perceive literally means "to take entirely", figuratively, means "to grasp with the mind(to view(看待)， to understand(理解)，to comprehend)"；

vt. be come aware of sth。

(2)示例

1.Virtual memory involves the separation of logical memory as perceived by developers from physical memory(《Operating System Concepts》第 390 页)。

在上面这个例子中，整句话的意思是“虚拟内存涉及将开发者所感知的逻辑内存与物理内存分离”。

2.His mouth fell open as he perceived the truth(当他意识到真相时，他的嘴张得大大的)。

之前一直不能很好的理解 perceive 的意思，大概是因为对 aware/awareness 的理解一直局限于“意识”，其实也可以扩展为为“对......的认识，感知，理解，明白”。

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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