The Purpose & Functionality of Operating Systems (AQA GCSE Computer Science)
Revision Note
The Purpose & Functionality of Operating Systems
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 five key areas:
Provide a user interface
Memory & processor management
I/O management & device drivers
Application & security management
File management
User Interface
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) |
|
|
Graphical (GUI) |
|
|
Menu |
|
|
Natural language (NLI) |
|
|
Memory & Processor Management
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)
Peripheral Management & Device Drivers
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
Application & Security Management
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
File Management
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
Worked Example
State four functions of an operating system [4]
How to answer this question
What does an operating system MANAGE?
Answer
Memory management
I/O device management
File management
Application management
Security management
Network management
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