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Introduction

overall 期末

  • 40 x 1.5 选择
  • 5 x 2 填空
  • 3-4 大题 memory(hard), synchronization, scheduling
  1. multi-programming, time-sharing
  2. OS events: interrupts and exceptions
  3. Timer: modifying the timer is done via privileged instructions
  4. Released the first Linux prototypes in late 1991

Main OS Services

  1. Process Management - a process is a program in execution
  2. Memory Management - keep track of memory use
  3. Storage Management - operate file-system management
  4. I/O Management - device-driver interface
  5. Protection and Security - 控制进程对由操作系统定义的资源的访问的机制 - 防御系统的内部和外部攻击

Processs

  1. Linkder Load

  2. OS is a resource abstractor and a resource allocator - define a set of logical resources and a set of well-defined operations - decides who gets what resource and when

  3. bootloader
  4. OS waits until an event occurs
  5. modern OSes allows multi-programming - Time-Sharing: Multi-programming with rapid context-switching
  6. Furthermore, there is no memory protection within the kernel - segmentation fault
  7. For instance, only the OS can:
  • Directly access I/O devices (printer, disk, etc.)
  • Manipulate memory management state 操作内存管理状态
  • Manipulate protected control registers
  • Execute the halt instruction that shuts down the processor

  1. MS-DOS had only one mode, because it was written for the Intel 8088(1979), which had no mode bit

  2. OS Events - The kernel defines a handler for each event type - Once the system is booted, all entries to the kernel occur as the result of an event - The OS can be seen as a huge event handler

  3. A system call is a special kind of trap

  4. To make sure that an interrupt will occur reasonably soon, we can use a timer

    • The timer interrupts the computer regularly

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