Operating Systems

Operating Systems

1. Managing resources

   • CPU
     • modern processors execute 4billion instructions every second
       • this is more than memory and secondary storage can keep up with
     • while the processors are waiting for other components to catch up they are doing nothing
       • OS allocate this dead time for the CPU to perform other instructions and task enabling MULTITASKING
   • multitasking
     • processors cannot do tasks simulataneously
       • instead they use time they are doing nothin gto do other instructions making it seem like they are doing two tasks at once
         • the OS has to keep tasks separate and manage the use of the accumulator and storage
   • interrupts
     • some tasks and processors are of very high importance and need priority over other instructions taking up the CPU's time
       • therefore interrupts are a thing, and stop all other executions by the CPU and makes it execute one specific instruction
     • interrupts can be triggered both by software or hardware
       • Hardware interrupts: mouse being moved, key being pressed, controller stick being moved
       • Software interrupts: warning screen needs to pop up if a task has failed, or a screen blanking for security
   • RAM
     • since processors allow multiple programs to run each program also needs RAM
       • OS then split the RAM into "pages" this gives each program allocated storage and RAM without letting them snoop on other programs RAM, due to only letting certain programs into certain "pages"
   • peripherals
     • these are devices that connect to a computer, like printers or controllers
   • drivers
     • OS use device drivers to communicate to different peripherals, these map the OS's commands to the device's commands
       • for example printing a charater on different branded printers, or using a controller from either Xbox or playsation

2. Interfaces

   • CLI
     • Command Line Interface
     • a text based interface where the user types commands and the result is shown as text. nearly every operating system provides this but are harder to use but are lightweight on the computer
       • ADVANTAGES
         • few system resources required
         • easy to automate (command can be stored in files)
       • DISADVANTAGE
         • Hard to learn
         • difficult to compare outputs of different programs
   • GUI
     • Graphical User Interface
     • the computer's function is represented graphically and controlled by touchscreen or mouse and keyboard
       • ADVANTAGES
         • easy to learn
         • lots of information shown at once
       • DISADVANTAGES
         • uses a lot of system resources
         • the complexity of code means there is more to go wrong