The Purpose & Functionality of Operating Systems (AQA GCSE Computer Science)

• System software can be further broken down in to two categories, operating system and utility software

What is an operating system?

• An operating system (OS) is software that provides an interface between the user and the hardware in a computer system
• An operating system hides the complexities of the hardware from the user, for example:
  • A user does not need to know 'where' on secondary storage data is kept, just that it is saved for when they want it again
• An operating systems main functions can be divided in to four key areas:
  • Provide a user interface
  • Memory & processor management
  • I/O management & device drivers
  • Application & security management
  • File management

What is a user interface?

• A user interface is how the user interacts with the operating system
• Examples of user interfaces include:
  • Command Line Interface (CLI)
  • Graphical User Interface (GUI)
  • Menu
  • Natural language (NLI)

What is a command line interface?

• A Command Line Interface (CLI) requires users to interact with the operating system using text based commands
• CLIs are more commonly used by advanced users
• Examples of CLIs are MSDOS (Microsoft Disk Operating System) and Raspbian (for Raspberry Pi)

What is a graphical user interface?

• A Graphical User Interface (GUI) requires users to interact with the operating system using visual elements such as windows, icons, menus & pointers (WIMP)
• GUIs are optimised for mouse and touch gesture input
• Examples of GUIs are Windows, Android and MAC OS

What is a menu interface?

• A menu interface is successive menus presented to a user with a single option at each stage
• Often performed with buttons or a keypad
• Examples include
  • Chip and pin machines
  • Vending machines
  • Entertainment streaming services

What is a natural language interface?

• A natural language interface (NLI) uses the spoken word to respond to spoken or textual inputs from a user
• Examples include
  • Virtual assistants - Amazon Alexa, Google Assistant, Siri
  • Search engines
  • Smart home devices

Advantages and disadvantages of user interfaces

Interface	Advantages	Disadvantages
Command line (CLI)	Uses less system resources Useful for automation of tasks Commands are often faster to type than navigating menus	Requires users to remember commands Typing errors are common Less intuitive than GUI
Graphical (GUI)	Intuitive and user-friendly Requires no previous knowledge to use Information is visual, making it easier to understand	Uses more system resources Can be slower to find and execute commands Can be frustrating when doing repetitive tasks
Menu	Simplicity Efficiency	Limited flexibility Accessibility issues
Natural language (NLI)	Can be used by people with disabilities Intuitive	Not always reliable Privacy concerns

What is memory management?

• Memory management is a process carried out by the operating system allocating main memory (RAM) between different programs that are open at the same time
• The OS is responsible for copying programs and data from secondary to primary storage as it is needed
• Programs and data require different amounts of RAM to operate efficiently and the OS manages this process
• RAM is allocated based on priority and fairness, for example, system applications (essential) may have a higher priority than user applications
• The OS dynamically manages the memory, adjusting allocation as needed to maintain optimal system performance
• Memory management makes multitasking possible

What is processor management?

• Processor management is a process carried out by the operating system dividing time (time slicing) in to small chunks and allocating them to different programs
• The CPU can only execute one instruction at a time, it can can execute billions of them in one second.
• The OS decides what programs get access to the CPU to give a user the perception of being able to use multiple programs at the same time (multitasking)

What is I/O management?

• Input/output (I/O) management is a process carried out by the operating system managing the way input and output devices interact with software
• The OS allocates system resources to inputs/outputs to ensure efficient operation
• I/O management makes plug-and-play (PnP) functionality possible, automatically detecting and configuring new inputs/outputs without the need for manually installing device drivers or power cycling the system

What is a device driver?

• A device driver is a piece of software used to control a piece of hardware
• Inputs/outputs require device drivers in order to be used by the operating system
• The OS has generic device drivers built in which makes basic compatibility possible and enables plug-and-play (PnP)
• In order for hardware to be used to its maximum capacity, often a separate device driver must be downloaded from the manufacturer
• Device drivers are OS specific and are regularly updated

What is application management?

• Application management is a process carried out by the operating that enables applications to talk directly to hardware and software through the use of application programming interfaces (APIs)
• The APIs provide a standardised way for applications to access system resources

What is security management?

• Security management is a process carried out by the operating system enabling different users to log onto a computer
• A system administrator is able to allocate different access rights for different users on a network
• The OS is able to maintain settings for individual users, such as desktop backgrounds, icons and colour schemes
• The OS audits (keeps a log of) files created by users, accesses, edits and deletes  

What is file management?

• File management is a process carried out by the operating system creating, organising, manipulating and accessing files and folders on a computer system
• The OS manages where data is stored in both primary and secondary storage
• File management gives the user the ability to:
  • Create files/folders
  • Name files/folders
  • Rename files/folders
  • Copy files/folders
  • Move files/folders
  • Delete files/folders
• The OS allows users to control who can access, modify and delete files/folders (permissions)
• The OS provides a search facility to find specific files based on various criteria