《Operating System Concepts》学习第 2 天，p2-p8 总结，总计 7 页。
一、技术总结
1.operating system
An operating system is software that manages a computer’s hardware。
2.system bus
data bus, address bus, control bus 统称为 system bus。
二、英语总结(生词：5)
1.myriad
(1)myriad: myrias("ten thousand")
Originally, myriad refered to the number ten thousand(10,000), but over time, it came to mean a very larege or countless number of sth.
示例：By now, you can probably see that the term operating system covers many roles and functions. That is the case, at least in part, because of the myriad designs and uses of computers(《Operating System Concepts》第5页)。
2.spacecraft
(1)space
c/u. an empty area(空间), an empty area outside Earth's atmosphere(宇宙，太空).
(2)craft
The sense expanded in Old English to include "skill, dexterity; art, science, talent" .
The meaning "small boat" is recorded by 1670s, probably from a phrase similar to vessels of small craft and referring either to the trade they did or the seamanship they required, or perhaps it preserves the word in its original sense of "power."
(3)pacecraft: space + craft.
c. a vehicle used for travel in space(太空飞船，宇宙飞船).
3.diversity
(1)diversify
assimilated form of dis-("aside") + vertere("to turn"). vi/vt. diversify literally means "to make different or varied.", to make more varied or different(使.....多样化)。
(2)diverse
adj. including many different types(多种多样的).
(3)diversity
s/u.the fact of many different types(多样性).
示例：To explain this diversity, we can turn to the history of computers(《Operating System Concepts》第5页)。
4.trajectory
(1)trajectory: trans-("across") + ject(from jacere"to throw")
c.Originally, trajectory referred to the path of a thrown object, and it later expanded to mean the course(过程) of anything moving or developing over time(轨迹).
示例：Computing started as an experiment to determine what could be done and quickly moved to fixed-purpose systems for military uses, such as code breaking and trajectory plotting, and governmental uses, such as census calculation(《Operating System Concepts》第5页)。
5.adequate
(1)adequate: ad-("to") + aequre("to make equal")
adj. equal to what is needed or desired, sufficient.It means matching a requirement or being sufficient for a purpose(足够的，合乎需求的).
示例：How, then, can we define what an operating system is? In general, we have no completely adequate definition of an operating system(《Operating System Concepts》第5页)。
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
本来计划是每天阅读 30 页的，但实际读下来却差距甚大——今天只阅读了 6 页，主要原因在于：一、英文单词。今天遇到很多生词，也有很多单词之前遇到过，但是学得不够细，又忘记了。二、对名称的不理解。例如：cable TV tuners(有限电视调谐器)，从字母上来说，英文、中文都能看懂，受限于没有见过实物，仅仅只是在头脑中形成一个概念，没有具象的理解。
本来想凑够了 30 页再发，算了，接受现实，慢慢来，不管每天的进度快慢，读一点是一点，不断记录，不断总结-日拱一卒，功不唐捐。
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
欢迎搜索及关注：编程人(a_codists)
