5.1. Operating System

Question 1

Need for OS

Answer 1

• A set of programs designed to run in the background
  on a computer system which
• Controls operation of computer system
• Provides a user interface
• Controls how computer responds to user’s
  requests
• Controls how hardware communicate
• Provides an environment in which application
  software can be executed
• OS hardware is unusable without an OS, as the OS
  acts as an interface since it controls communication
  between user and hardware

Question 2

Key Management Tasks

Answer 2

• (Main) Memory Management
• Memory protection to ensure 2 programs do not
  try to use same memory space
  Paging
• Use of virtual memory

Question 3

File Management

Answer 3

• Provides file naming conventions
• Maintains a directory structure
• Allocates space to particular files

Question 4

Security Management

Answer 4

• Proves usernames & passwords
• Ensures data privacy
• Prevents unauthorized access
• Carries out automatic backup

Question 5

Hardware (input/output/peripherals) Management

Answer 5

• Installation of appropriate driver software
• Controls access to data sent to and from
  peripherals
• Receives & handles interrupts from hardware
  devices

Question 6

Processor Management

Answer 6

• Enables multiprogramming and multitasking
• Resolution of conflicts when 2 or more processes
  requires the same resource
• E.g. via Round-robin method

Question 7

Utility Software

Answer 7

• Disk Formatter
• Virus checker
• Defragmentation Software
• Disk contents analysis/disk repair software
• File Compression
• Back-up Software
• Program Libraries
• Dynamic Link Library (DLL) files

Question 8

Disk Formatter

Answer 8

• Prepares a hard disk to allow data to be stored on
  it
• Deletes any existing data on disk
• Performs formatting, process where computer
  ‘draws lines’ on disk surface to split it into small
  areas

Question 9

Virus checker

Answer 9

• Checks for and then removes any viruses found
• Constantly checks all incoming and outgoing files

Question 10

Defragmentation Software

Answer 10

• Files can be big so have to be stored in multiple
  sectors, which can result in fragmentation
  (contents of file scattered across >2 noncontiguous sectors)
• Fragmentation slows down disk access and thus
  the performance of the entire computer.
• Defragmenting software works by physically
  reorganizing disk contents (files) such that they
  are stored in contiguous sectors.
• This defragmentation reduces number of
  movements of the read/write heads require to
  access the disk contents, hence increasing
  computer performance
• The defragmentation also creates larger
  contiguous free space regions

Question 11

Disk contents analysis/disk repair software

Answer 11

• Software utility for visualization of disk space
  usage
• Gets size for each folder and files, and generates a
  graphical chart showing disk usage distribution
  according to folders or other user defined criteria.
• Allows disk to report errors (e.g. “bad sector”)
• Software will attempt to offer a solution

Question 12

File Compression

Answer 12

• Reduces file size by removing redundant data in
  files
• Causes improvements in the computer’s
  performance by reducing the data that needs to
  be stored

Question 13

Back-up Software

Answer 13

• Makes copy of files on another storage medium in
  the event of a hard drive failure, user error,
  disaster or accident.
• Should be a regular process
• Can provide synchronization between devices

Question 14

Program Libraries

Answer 14

• Pre-written code that can be linked to a software
  under development without any amendments
• Can perform common or complex tasks
  Takes the form of classes
• Benefits:
  Saves time: less code needs to be written
  Smaller testing time: pre-tested and used by
  others
  Library file be a complex algorithm which the user
  need not understand for using it

Question 15

Dynamic Link Library (DLL) files

Answer 15

• Shared library file that contains code and data
• Code saved separately from the main .EXE file,
  reducing the .EXE file’s size
• Code only loaded to main memory when required
• DDL file can be made available to several applications
  simultaneous, thus reducing strain on memory
• DLL files act as modules in more complex programs,
  making it easier to install and run updates