OS Overview

Key Characteristics of Operating System §

• Driven by interrupts
  • Event driven system
  • Software interrupt
    • Interrupts caused by the applications running on the system. Anytime the application wants to do something with the OS it will inevitably cause a software interrupt. Think how malloc gets to a point to use sbrk which causes an interrupt and gets the OS to do something.
  • Hardware interrupt
    • Hardware components will interrupt the Operating System to let it know that it has finished it’s task, for example a disk causing an interrupt to let the OS know it finished transferring data
    • Within the processor, some components can raise interrupts
• Virtualizing resources
  • The OS creates illusions to allow easy access to all the hardware resources
  • CPU
    • Processor threads
  • Memory
    • Virtual Memory
  • I/O device
• Enabling concurrency
  • XINU only has 1 physical CPU, but it can still support concurrency via OS
  • Processes
  • Threads
• Persistency

Lack of OS Security §

• A lack of OS security leads to all kinds of malware
  • botnets
  • virus
    • why do they spread so quickly?
  • spyware, keylogger, identity theft
  • ransomware