The Purpose & Functionality of Operating Systems (Cambridge (CIE) IGCSE Computer Science)
Revision Note
Written by: Robert Hampton
Reviewed by: James Woodhouse
What is an operating system?
An operating system (OS) is software that manages computer hardware and provides a platform for running applications
It provides an interface between the user and the hardware in a computer system
It 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 eight key areas
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
Handling Interrupts
What is interrupt handling?
Interrupt events require the immediate attention of the central processing unit
In order to maintain the smooth running of the system, interrupts need to be handled and processed in a timely manner
For example, if a user clicks cancel on a file conversion process, a signal is sent from the mouse, interrupts the processor, and the operating system will trigger the cancellation routine
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) |
|
|
Peripheral Management & Device Drivers
What is peripheral management?
Peripheral management is a process carried out by the operating system managing the way peripherals (hardware) interact with software
The OS allocates system resources to peripherals to ensure efficient operation
Peripheral management makes plug-and-play (PnP) functionality possible, automatically detecting and configuring new peripherals 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
Peripherals 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
Memory Management & Multitasking
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 multitasking?
Multitasking is a process made possible by the OS simultaneously managing system resources (memory, CPU etc) to give a user the perception of being able to use multiple programs at the same time
The OS splits tasks and allocates system resources based on a priority
The CPU can only execute one instruction at a time, it can can execute billions of them in one second.
This makes it appear that multiple programs are running at the same time
Providing a Platform for Running Applications
Operating systems provide a platform on which application software can run, this is mainly by allowing software access to system resources
For example, if a computer game has intensive graphics and online play, the operating system will grant it access to the GPU and the network card
Organisation of application layer, operating system components, and input/output
Providing System Security
What is system security?
Operating systems provide various security features such as password-protected system accounts, a firewall, virus scanning and file encryption
Password-protected system accounts are a very common feature in operating systems
System accounts can also be restricted from performing certain actions, e.g. editing network settings, installing unapproved software, changing the account settings of other users
User Management
What is user management?
User management is a process carried out by the operating system enabling different users to log onto a computer
The OS is able to maintain settings for individual users, such as desktop backgrounds, icons and colour schemes
A system administrator is able to allocate different access rights for different users on a network
Worked Example
Ella uses her computer to create artwork for a magazine
Ella makes use of system software.
One type of system software is the operating system.
Identify and describe two functions of an operating system [6]
How to answer this question
Break down the 6 marks, 1 mark each for identifying a function of the operating system. For each function you need to make 2 points about how they work
Answer
Memory management
Allocates memory to programs currently in use
Gets data from RAM
Stores data in RAM
File management
Creating/editing/renaming files
Creating/editing/renaming folders
Movement of files/folders
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