A-level Computing 2009/CIE/Operating Systems

Basic process flow:

   __________________________________________________________________________________________________________
  |                                      | Yes                          | Yes                                | Yes
  V                                      |                              |                                    |

Start - Fetch - Decode - Execute - Check for interrupt - No - Check for more instructions - No - Return to previous instruction? - No - End

Operating system is made out of 4 components:

     User interface  -  provides an interface for the user to communicate with the hardware

     Kernel          -  translates the inputs from the U.I. in Machine Code for the hardware ( device drivers and utilities ) to understand

     Device drivers  -  The set of instructions that the hardware can understand ( a user manual of the device for the kernel , basically )

     Utilities       - Power management, Managing Fragmentation, System Security etc.

The Scheduler

  The Scheduler is a part of the OS that manages how much time each process spends using the processor.