Operating System 简明教程
Operating System - Needs
操作系统是一种软件，可帮助应用程序软件、系统软件与计算机硬件交互。操作系统管理系统的硬件和其他资源，并执行文件管理、内存管理、进程管理、输入/输出处理、磁盘驱动器、打印机、扬声器等外围设备管理等基本任务。
An Operating System is a software which helps applications softwards, system softwares to intertact with computer’s hardware. Operating System manages a system’s hardware and other resources and performs basic tasks like file management, memory management, process management, input/output handling, peripheral device management like disk drives, printers, speakers etc.
计算机中最流行的操作系统包括 Windows、Linux、Unix，以及手机中的 Android 和 iOS。
Most popular Operating Systems in Computers include Windows, Linux, Unix and in Mobiles, Android and iOS.
Need for an Operation System
操作系统是任何计算机软件的必要组成部分。没有操作系统，我们甚至无法操作计算机。操作系统的首要目的是使应用程序（软件）能够与计算机硬件交互，并管理系统的硬件和软件资源。以下是操作系统的部分显着特点，它们可以帮助我们理解操作系统的必要性。
An Operating System is an essential part of any computer software. Without Operating System, we cannot even operate a computer. The primary purpose of an Operating System is to enable applications (softwares) to interact with a computer’s hardware and to manage a system’s hardware and software resources. Following are some of the salient features of an Operating System which can help us to understand the need of an operating system.
Interface between User and Computer
操作系统提供了用户与计算机之间的接口。例如，Windows 操作系统提供 GUI（图形用户界面），用户可以通过单击图标、使用键盘键入单词、使用鼠标在计算机上执行许多操作，从而直观地与计算机交互。同样，Unix 提供命令行界面，用户可以在其中键入命令执行特定操作。
An Operating System provides an interface between user and a computer. For example, Windows Operating System provides a GUI, Graphical User Interface where a user can visually interact with computers by clicking icons, typing words using keyboard, using mouse to perform many actions on a computer. Similarly Unix provides a command line interface, where a user can type command to perform a particular operation.
Booting Process
当计算机打开时，主内存中没有应用程序。操作系统会首先被加载到主内存中，然后辅助用户登录到机器。这种计算机或移动设备的初始启动称为启动过程。没有操作系统，启动将无法完成。
When a computer is switched on, there is no application in main memory. First Operating System is loaded in main memory which then assist user to log on to the machine. This initial startup of a computer or mobile device is known as booting process. Without Operating System, booting cannot happen.
Managing Input/Output Devices
计算机具有鼠标、键盘、扬声器、扫描仪、打印机等多个外围设备。操作系统管理所有这些连接到计算机的设备。它帮助安装设备驱动程序。例如，Windows 操作系统提供了控制面板来管理所有硬件设备，以检查它们的运行状况。如果任何设备无法正常运行，它还提供了故障排除选项。
A computer has multiple peripheral devices like mouse, keyboard, speakers, scanner, printers. Operating System manages all of these devices connected to the computer. It assists in installing the device drivers. For example, windows operating system provides a control panel to manage all hardware devices, to check their health. It also provides options to troubleshoot if any device is not functioning properly.
Multitasking Support
操作系统在多任务处理环境中确保每个任务或准确地说每个进程在需要执行一些计算时获得其 CPU 共享，而其他进程则可以忙于 I/O 操作，例如写入主存储器或辅助存储器或等待用户输入或写入打印机等。通过这种方式，借助操作系统，用户可以在计算机上同时执行多项任务，例如在编写 Word 文档时一边欣赏音乐、一边浏览网页，并在系统中保持多个应用程序处于打开状态，以便可以在其当前状态下打开任何应用程序。
An operating system, in a multitasking environment, ensures that each task or precisely a process gets its CPU share when it needs to do some computation while other process can be busy in I/O operation, like writing to primary or secondary memory or waiting for user input or writing to printer and so on. This way, with the help of Operating System, a user can perform multiple tasks simultaneously on a computer like listening music while working on word document, browse web and keep multiple application open in system so that any application can be opened in its current state.
Platform for Application Softwares
操作系统为应用程序软件提供一个环境来执行。应用程序软件不需要了解底层机器语言。它们用于特定的操作系统。例如，适用于 Windows 的 Word 文档软件在 Linux 机器上无法运行。操作系统提供许多服务，例如 I/O 操作、文件系统操作、资源分配和保护。
Operating System provides an environment to Application Softwares to execute. Application softwares need not to know about underlying machine language. They are intended for a particular Operating System. For example, a Word document software for Windows will not work on Linux machine. Operating System provides many services like I/O operations, file system manipulation, resource allocation and protection.
Memory Management
操作系统管理主内存和磁盘。操作系统可以通过虚拟内存管理增加可用物理内存。它在程序执行期间在主内存和磁盘之间来回移动进程。通过内存管理，操作系统跟踪分配给某个进程或处于空闲状态的每个内存位置，并根据需要分配内存。
Operating system manages primary memory and disk. Operating System can increase available physical memory via virtual memory management. It moves processes back and forth between main memory and disk during a program execution. Via memory management, operating system keeps track of each and every memory location, being allocated to some process or being free and allocates memory accordingly.
System Files Management
操作系统提供控制和界面在磁盘上的文件系统中创建/删除文件、目录。它提供权限管理，例如授予对文件或目录的只读或读写权限或显示/隐藏它们。操作系统还提供创建文件备份并在需要时还原它们的选项。
Operating System provides control and interface to create/delete files, directories in underlying file system on disk. It provides permission management like to give readonly or read-write permission to files or directories or to show/hide them. An operating sytstem also provides options to create backup of files and to restore them when needed.
Security Management
操作系统提供许多安全功能，以保护系统及其资源。它确保控制对系统资源的所有访问。外部 I/O 设备受到保护，使其免受无效访问尝试的侵害，操作系统通过密码或其他用户身份验证方式为每个用户提供身份验证功能。
Operating System provides many security features to safeguard system and its resources. It ensures that all access to system resources is controlled. External I/O devices are protected from invalid access attempts and an Operating System provides authentication features for each user by means of passwords or other ways of authenticating a user.
Error Management
随时随地都可能发生错误。例如，错误可能发生在 CPU 操作期间、在设备上执行 I/O 操作期间或在内存硬件中。操作系统通过持续检查可能出现的错误并采取适当措施来确保计算正确和一致，从而处理此类问题。
Errors can occur anytime and anywhere. For example, an error may occur during a CPU operation, performing I/O operations on devices or in the memory hardware. Operating System takes care of such issues by constantly checking for possible errors and by taking an appropriate action to ensure correct and consistent computing.