Types of Operating Systems

• Single-User Single-Tasking OS: Allows one user to perform one task at a time (e.g., MS-DOS)
• Single-User Multi-Tasking OS: Allows one user to perform multiple tasks simultaneously (e.g., Windows, macOS)
• Multi-User Multi-Tasking OS: Allows multiple users to perform multiple tasks simultaneously (e.g., Linux, Unix)

Operating System Components

• Kernel: The core of the OS, responsible for managing hardware resources and providing services to applications
• Device Drivers: Software components that allow the OS to interact with hardware devices
• System Libraries: Pre-built code libraries that provide common functionality to applications
• System Utilities: Programs that perform specific maintenance or management tasks (e.g., disk formatting, backup)

Process Management

• Process: A program in execution, including its current state and resources
• Process Scheduling: The OS decides which process to run next, and for how long
• Process States:
  • Newborn: A new process is created
  • Running: The process is currently executing
  • Waiting: The process is waiting for a resource or event
  • Ready: The process is waiting for the CPU to become available
  • Zombie: A process that has finished executing but still has resources allocated

Memory Management

• Memory Hierarchy: The organization of memory into levels of increasing size and decreasing speed (e.g., registers, cache, RAM, disk)
• Virtual Memory: A combination of physical RAM and secondary storage (e.g., hard disk) to provide a larger address space
• Memory Allocation: The OS manages memory allocation and deallocation for applications

File Systems

• File System: A hierarchical organization of files and directories on storage devices
• File System Types:
  • Local File System: A file system stored on a local device (e.g., hard disk)
  • Network File System: A file system stored on a remote device (e.g., server)
• File System Operations: Create, delete, read, write, and manage files and directories

Security

• Access Control: The OS restricts access to resources based on user identity and permissions
• Authentication: The process of verifying user identity
• Authorization: The process of determining what actions a user can perform on a resource
• Encryption: The process of protecting data from unauthorized access

操作系统类型

• 单用户单任务操作系统：允许一个用户在一个时间点执行一个任务（例如 MS-DOS）
• 单用户多任务操作系统：允许一个用户在同一时间执行多个任务（例如 Windows、macOS）
• 多用户多任务操作系统：允许多个用户在同一时间执行多个任务（例如 Linux、Unix）

操作系统组件

• 核心：操作系统的核心，负责管理硬件资源和提供服务给应用程序
• 设备驱动程序：允许操作系统与硬件设备交互的软件组件
• 系统库：提供常见功能给应用程序的预编译代码库
• 系统实用程序：执行特定维护或管理任务的程序（例如磁盘格式化、备份）

进程管理

• 进程：一个程序在执行时，包括其当前状态和资源
• 进程调度：操作系统决定哪个进程下一个运行，并运行多长时间
• 进程状态：
  • 新生：一个新进程被创建
  • 运行：进程当前正在执行
  • 等待：进程正在等待资源或事件
  • 就绪：进程正在等待 CPU becomes available
  • 僵尸：一个已经执行完毕但仍然有资源分配的进程

内存管理

• 内存层次：内存的组织结构，按大小和速度递减（例如寄存器、缓存、RAM、磁盘）
• 虚拟内存：物理 RAM 和辅助存储（例如硬盘）的结合，提供更大的地址空间
• 内存分配：操作系统管理应用程序的内存分配和释放

文件系统

• 文件系统：存储设备上的文件和目录的层次组织
• 文件系统类型：
  • 本地文件系统：存储在本地设备上的文件系统（例如硬盘）
  • 网络文件系统：存储在远程设备上的文件系统（例如服务器）
• 文件系统操作：创建、删除、读取、写入和管理文件和目录

安全

• 访问控制：操作系统根据用户身份和权限限制资源访问
• 身份验证：验证用户身份的过程
• 权限授权：确定用户可以对资源执行的操作
• 加密：保护数据免受未经授权访问的过程