operating sytems

operating sytems

1. CPU

   • modern ones process 4 billion instructions every second
   • An OS will allocate CPU time to different processes
   • each application can run as if it was the only one

2. multi tasking

   • two tasks aren't happening simultaneously but the processing is so fast it looks like it is
   • it runs commands from each task seperately

3. interrupts

   • some tasks are more important so the OS pauses the fetch execute to execute the high importance task
   • the OS manages interrupt requests, backing up existing processes to resume them later
   • hardware interrupts
     • when the mouse is moved
     • a keyboard key is pressed
     • a games controller stick is moved
   • software interrupts
     • a warning box needs to pop up
     • the screen needs to be blanked for security

4. RAM

   • two programs running can read each other's RAM including private info
   • so the OS stops this by splitting up the RAM so that each program can't read private info from each other
   • the split up RAM is called "pages".

5. backing stores

   • OS can often manage this on its own
   • they are storage devices used to keep important backups of files
   • The OS will make backups regularly

6. peripherals

   • OS handles controllers so game designers have to only make one code

7. drivers

   • They are used to comunicate with other peripherals
   • a device driver maps the commands of a system to the device's

8. security

   • OS verifies usernames and passwords as well as ensure damaging programs don't damage system files

9. interface

   • There are two user interfaces that are commonly used by OSs GUI (graphical user interface) and CLI (command line iterface)
   • graphical user interface
     • used by most PCs
     • GUI represent the functions graphically and they often run on windows and can display multiple at once
   • command line interface
     • A text based interface that uses commands
     • these are provided by nearly every OS
     • harder to use but are lightweight and robust

10. print spooling

    • If a program needs to print a document, I tell the operating system to print it. The operating system will then spool the print job