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Basic Operating System Concepts

  • Every computer has a basic set of programs called the the operating system
    • The most important program in the set is called the kernel
      • It is loaded into ram when the system boots
    • 1. OS must interact with hardware, 2. provide environment for program
  • In Unix, if a program wants to use hardware it needs to issue request to OS
    • Kernel will interact on behalf of user program if correct access levels
    • Enforced by forbidding user programs to directly interact with low level hardware and arbitrary memory
    • Unix has 2 privilege levels
      • User mode: Needs to request kernel to schedule task
      • Kernel mode: Direct access to hardware

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