operating systems

operating systems

1. CPU

   • Modern processors can execute 4 billion instructions every second.
   • An OS will make use of this dead time by allocating CPU time to different processes
   • A process is a running application

2. multi-tasking

   • multi tasking is where a processor appears to be doing two tasks simultaneously
   • In reality the processor runs commands from each task separately, filling in the time when it is waiting for other components.
   • simply alternating the instructions will result in memory being overwritten

3. GUI

   • Advantages
     • easy to learn
     • lots of information shown at once
   • Disadvantages
     • Complexity means there is more to go wrong
     • Uses a lot of system resources

4. Interrupts

   • Some tasks and processes are of high importance and can’t wait until the OS is able to allocate CPU time
   • An interrupt is a method to immediately pause execution of all processes and execute a new one
   • The OS will manage interrupt requests, backing up existing processes so they can be resumed when the interrupt is finished
   • Interrupts can be triggered by hardware or software

5. CLI

   • Advantages
     • Few system resources required
     • Easy to automate (commands can be stored in file)
   • Disadvantages
     • Difficult to compare outputs of different programs
     • Hard to learn