1.2.1 System software:

• What does the term 'operating system' refer to?

  A collection of programs providing user interface
• Why are operating systems essential for devices?

  They manage memory and resources for users
• Name two popular desktop operating systems.

  Windows and macOS
• Name two popular mobile operating systems.

  iOS and Android
• What features do operating systems provide?

  • Memory management (paging, segmentation, virtual memory)
  • Resource management (scheduling)
  • File management (moving, editing, deleting files)
  • Input/Output management (device drivers)
  • Interrupt management
  • Utility software (disk defragmenter, backup)
  • Security (firewall)
  • User interface
• What is the role of memory management in operating systems?

  To share memory fairly among programs
• How does segmentation differ from paging?

  Segmentation uses logical divisions of varying sizes
• What is virtual memory used for?

  To use hard drive space as additional RAM
• What is disk thrashing?

  When pages are swapped too frequently between memory
• What are interrupts in operating systems?

  Signals indicating a process needs attention
• How are interrupts prioritized?

  Stored in order of priority in a queue
• What is paging in memory management?

  Memory split into equal-sized sections called pages
• What is the purpose of the Interrupt Service Routine (ISR)?

  To service interrupts fairly by the processor
• When does the processor check the interrupt register?

  At the end of each Fetch-Decode-Execute cycle
• What happens if a higher priority interrupt is detected?

  Current registers are saved, ISR is loaded
• What are the types of scheduling algorithms?

  1. Pre-emptive

  • Jobs actively started and stopped
  • Examples: Multilevel Feedback Queues, Round Robin

  1. Non pre-emptive

  • Jobs run to completion once started
  • Examples: First Come First Served, Shortest Job First
• What is the Round Robin scheduling algorithm?

  Each job gets a time slice to execute
• What is the First Come First Served (FCFS) scheduling algorithm?

  Jobs processed in order of arrival
• What are Multilevel Feedback Queues?

  Multiple queues ordered by different priorities
• What is the Shortest Job First scheduling algorithm?

  Jobs ordered by time required for completion
• What is the Shortest Remaining Time scheduling algorithm?

  Jobs ordered by time left for completion
• What is a distributed operating system?

  Runs across multiple devices for load sharing
• What are the types of operating systems?

  • Distributed
  • Embedded
  • Multi-tasking
  • Multi-user
  • Real Time
• What is an embedded operating system?

  Designed for specific tasks on specific devices
• What does a multi-tasking operating system do?

  Allows tasks to run seemingly simultaneously
• What is a multi-user operating system?

  Supports multiple users on one computer
• What is a real-time operating system?

  Performs tasks within a guaranteed time frame
• What does BIOS stand for?

  Basic Input Output System
• What is the role of BIOS during startup?

  Runs key tests before loading the OS
• What does POST stand for?

  Power-on self test
• What do device drivers do?

  Allow OS to interact with hardware
• Why are device drivers specific to architecture?

  Different drivers are needed for different devices
• What is a virtual machine?

  A software implementation of a computer system
• What is intermediate code?

  Code between machine code and object code
• What is one advantage of using virtual machines?

  Saves time and money for testing
• What is a disadvantage of running intermediate code in a virtual machine?

  It can be considerably slower than low-level code
• What are other uses of virtual machines?

  • Protection from malware
  • Running incompatible software
• How do virtual machines protect from malware?

  Malware affects the VM, not the device
• How do virtual machines run incompatible software?

  By simulating different operating systems