WHAT IS AN OPERATING SYSTEM?
Operating systems turn ugly hardware into beautiful abstractions.
Operating System:
1.A clean abstract set of resources instead of the messy hardware ones and managing these
hardware resources ( … instruction set, memory organization, I/O, and bus structure ).
2.No sane programmer would want to deal with this disk at the hardware level. Instead, a piece of software, called a disk driver, deals with the hardware and provides an interface to read and write disk blocks, without getting into
the details. Operating systems contain many drivers for controlling I/O devices.
But even this level is much too low for most applications. For this reason, all operating systems provide yet another layer of abstraction for using disks: files. Using this abstraction, programs can create, write, and read files, without having to deal with the messy details of how the hardware actually works.
3.This abstraction is the key to managing all this complexity. Good abstractions turn a nearly impossible task into two manageable ones. The first is defining and implementing the abstractions. The second is using these abstractions to solve the problem at hand. One abstraction that almost every computer user understands is the file, as mentioned above.
什麼是操作系統？
操作系統把醜陋的硬件變成美麗的抽象。
操作系統:
1.一個乾淨的抽象資源集，而不是混亂的硬件資源集，並管理這些資源
硬件資源（...指令集、內存組織、I/O和總線結構）。
2.沒有一個理智的程序員會想在硬件層面處理這個磁盤。相反，一個叫做磁盤驅動程序的軟件處理硬件，並提供一個讀寫磁盤塊的接口，而不需要進入操作系統包含許多用於控制I/O設備的驅動程序。但是對於大多數應用程序來說，即使是這個級別也太低了。
出於這個原因，所有的操作系統都爲使用磁盤提供了另一個抽象層：文件。使用這個抽象，程序可以創建、寫入和讀取文件，而不必處理硬件實際工作方式的混亂細節。
3.這個抽象是管理所有這些複雜性的關鍵。好的抽象將一個幾乎不可能的任務變成兩個可管理的任務。第一個是定義和實現抽象。第二個是使用這些抽象來解決手頭的問題。幾乎每個計算機用戶都理解的一個抽象是文件，如上所述。