• context
    The operating system keeps track of all the state information that the process needs in order to run. This state, which is known as the context, includes information such as the current values of the PC, the register file, and the contents of main memory.

  • context switching
    In either case, a single CPU can appear to execute multiple processes concurrently by having the processor switch among them. The operating system performs this interleaving with a mechanism known as context switching.
    When the operating system decides to transfer control from the current process to some new process, it performs a context switch by saving the context of the current process, restoring the context of the new process, and then passing control to the new process.

  • Kernel
    The kernel is the portion of the operating system code that is always resident in memory
    Note that the kernel is not a separate process. Instead, it is a collection of code and data structures that the system uses to manage all the processes.

  • Trampoline page

Goal of OS

  • run multiple applications
  • isolate them
  • multiplex them
  • share