WHOLE TOPIC

• What is the primary function of an Operating System (OS)?

  Provide an interface between user and computer
• What are the main features of an Operating System?

  • Memory management
  • Resource management
  • File management
  • Input Output Management
  • Interrupt management
  • Utility software
  • Security
  • User interface
• What is an algorithm?

  A set of instructions to solve a problem
• What must be clearly defined in an algorithm?

  Inputs must be clearly defined
• What is a requirement for an algorithm regarding outputs?

  Must always produce a valid output
• How should an algorithm handle invalid inputs?

  Must be able to handle invalid inputs
• What is a stopping condition in an algorithm?

  Must always reach a stopping condition
• Why is documentation important for algorithms?

  Must be well-documented for reference
• What is the purpose of comments in algorithms?

  Must be well-commented
• What is the role of memory management in computers?

  Manage available memory and share it
• What is paging in memory management?

  • Memory is broken into equal-sized parts called pages
  • Pages are swapped between main and virtual memory
• What is segmentation in memory management?

  • Memory is split into segments of varying sizes
  • Segments represent the logical flow and structure of a program
• What is virtual memory?

  • Part of the hard drive used as RAM
  • Access is slower than RAM
  • Paging moves inactive sections to virtual memory
• What is an interrupt?

  A signal needing processor attention
• How are interrupts prioritized?

  Have different priorities
• Where are interrupts stored?

  Stored in an interrupt register
• What happens at the end of the fetch, decode, execute cycle regarding interrupts?

  Interrupt register is checked
• What occurs if an interrupt has a higher priority than the current task?

  Registers are transferred into a stack
• What is loaded into RAM during an interrupt?

  The appropriate Interrupt Service Routine (ISR)
• What is set when an ISR begins?

  A flag is set
• When is the flag reset during an ISR?

  When the ISR has finished
• What is a virtual machine?

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

  Halfway between machine code and object code
• What is a benefit of virtual machines?

  Helps protect from malware
• What is applications software?

  Used by end users for specific tasks
• What is systems software?

  Manages computer resources for performance
• What is utility software?

  Maintains OS performance with specific functions
• What is scheduling in operating systems?

  • OS schedules processor time between programs
  • Jobs are held in a queue
  • Pre-emptive and non-pre-emptive routines manage jobs
• What is the Round Robin scheduling routine?

  Each job gets a time slice to run
• What happens when a job uses its time slice in Round Robin?

  It returns to the start of the queue
• What is the First Come First Served routine?

  Jobs processed in order they entered queue
• What is the Multilevel Feedback Queue routine?

  Uses multiple queues with different priorities
• What is the Shortest Job First routine?

  Queue ordered by amount of processor time needed
• What is the Shortest Time Remaining routine?

  Queue ordered by time left to completion
• What are the advantages and disadvantages of scheduling routines?

  Advantages:

  • All jobs are eventually attended to
  • Easy to implement
  • Considers job priority
  • Works well for batch systems
  • Increased throughput

  
  

  Disadvantages:

  • Longer jobs take much longer
  • Takes no account of priority
  • Requires additional processor time to order the queue
• What are the types of operating systems?

  • Distributed: Runs across several devices
  • Embedded: Specific small tasks, limited functionality
  • Multi-tasking: Simultaneous task completion
  • Multi-user: Several users on a single computer
  • Real-time: Tasks performed within a guaranteed time frame
• What does BIOS stand for?

  Basic Input Output System
• What does BIOS do when a computer turns on?

  Runs tests and loads the main OS
• What is the Power On Self Test (POST)?

  Ensures all hardware is connected and functional
• What are the advantages and disadvantages of open source software?

  Advantages:

  • Provided with source code
  • No license required
  • Free community support
  • High quality due to many contributors
  • Free to use

  
  

  Disadvantages:

  • Variable quality code
  • Not always well supported
  • Less secure