Operating Systems

Operating Systems

1. CPU

   • Multi-tasking
     • An OS manages
   • Modern processors can execute 4 billion instructions every second. This is more than memory and secondary storage can keep up with. A processor doesn't do anything while these other components catch up with it. An OS will make use of this time by allocating CPU time to different processes.

2. Interrupts

   • Some tasks and processes are of higher importance than others and can't wait for time to be allocated to them by the OS, so the OS triggers an interrupt, stopping all other processes allowing for the important one to run.
   • Hardware interrupts
     • A hardware interrupt is triggered by hardware
   • software interrupts
     • A software interrupt can be triggered by any application

3. Interfaces

   • GUI
     • Graphical user interfaces allow the functions of a computer to be displayed in graphical form, operating systems use GUI to allow the user to operate the computer in an easy and understandable manner.
   • CLI
     • Command Line interfaces are text based interfaces. They allow the user to type commands, giving the results in the form of text. These are harder to use and understand, but are simpler for the computer to run and are less likely to experience errors than GUI.

4. RAM

   • OS control the allocation of RAM. In order to ensure there is enough memory for each program that is running, Ram is split into “pages”. Each page is presented to its program as if it is the only memory the system has. This prevents programs from viewing data from other programs, protecting personal details stored in one program being stolen.

5. Backing Stores

   • Backing stores are storage devices used to keep backups of important files. Operating systems can often manage this for the user. The OS will make regular backups in the right format an appropriate device (Cloud, Tape or Disk).

6. Peripherals

   • a peripheral is a device connected to the computer. Operating systems can handle different types of devices allowing them to be used.