When you switch your computer on, ther operating system (OS) is located and loaded into RAM so the computer can start up. The OS allows you to interact with the programs and data using it's USER INTERFACE. An OS on it's own doesn't allow you to create documents, emails, photos etc... it is a PLATFORM for application software to run.
Operating Systems or 'system software' manages and controls all of the computer's hardware. It runs the entire time your computer is on and provides the user interface so that you can manage the programs and data.
Task and Memory management - Most users run several pieces of software at once, but are not interacting with each piece of software at the same time. Even when the software is running but not being used, it needs to be kept in the computers memory so that when it is needed, it can become active quickly. The OS should also be able to shut down/kill/close the apps without it affecting the other ones running. If programs need to use system devices such as the printer, it is the OS' job to manage this too.
Security management - Users can login to an operating system with a username and password to access their documents and applications individual to them. Users can also be assigned permissions to whatever level of permissions they require.
Providing a user interface - This allows a user to interact with and operate the computer. This will either be through a Command Line Interface (CLI) such as MS-DOS or Terminal where the user uses a keyboard to type in commands, or a Graphical User Interface (GUI - 'goo eee') which is operated typically with a point and click device such as a mouse or track pad. The interface allows users to start and stop programs, switch between running applications and create, copy, move, or delete files.
Communicating with all hardware - The OS controls all hardware such as disk drives, screens, printers, pointing devices... basically anything attached to the computer. Operating Systems use software called device drviers to understand how to communicate with the various hardware devices, meaning even hardware released years after an operating system can still function correctly with the correct drivers provided on CD or through a website online.
Common Operating Systems
Windows - Most common operating system with over 80% market share globally. Windows 10 is the latest version available via a subscription model.
Mac OS - Apple's OS for their Mac computers. Based on UNIX to ensure high level security. Mac OS will only run on Apple hardware.
Unix - Developed in the 1970s, this is a popular choice for high end hardware like super computers and mainframes due to its high levels of security.
Linux - Free software with the kernel available as open source so that new distros can be made by anybody. The most popular distributions currently are Ubuntu and Fedora. RedHat started as a free OS, but became a commercial business.
iOS - Mobile operating system that runs on iPhones and iPads. Currently version 11. Shares several features with Mac OS to allow easy data exchange and UI familiarity, such as iCloud.
Android - based on Linux and developed by Google, this is another mobile operating system aimed at smartphones and tablets. Versions have also been made available for smart televisions.
Defragmentation - Optimises hard disk performance by arranging data from files into contiguous sectors (ie. putting them in order together)
Backup - Used to compress and back up (make copies of) important files
Encryption - Scrambles files, folders and disks so thay they cannot be viewed or manipulated if the computer is stolen.
System monitoring - Keeps track of hardware efficiency as processor and memory usage, and optimises them to improve performance.
Disk clean up - Detects and deletes unnecessary files for example, temporary Internet files from the browser.
Accessibility - Sets options for disabled users such as screen contrast, or larger font sizes for on screen menus.
Anti-virus - Used to detect and remove malicious viruses, trojan horses and spyware.
System updates - Keeps the system up to date with the latest security and performances 'patches' (small improvements to the code)
Compression software - Compresses files to save disk space or network bandwidth. Decompresses them again when needed.
Application software allows a user to perform tasks, such as word processing, financial calculations, and image editing.
Office apps contain applications for word processing, creating spreadsheets, presentations and databases. Microsoft Office is a popular Office Suite available on a subscription basis called Office 365, or LibreOffice which is free. Mobile apps as the name suggests are for mobile devices and are usually distributed via an online store such as Apple's App Store, or Google's Play Store. gaming apps, video editing, image editing,audio editing, Note taking,
Computer software is a form of intellectual property so is protected by copyright laws. Depending on the software, they have different restrictions; whether the software can be modified and if the source code is available.
Commercial software is licensed or sold for profit by the company that created it. The licenses are very strict in order to prevent the software being copied or modified at all. Microsoft, Apple, Adobe and Autodesk are companies with lots of commercial software.
Shareware is distributed for no cost and is free to use for a limited period of time (anywhere from 7 to 30 days usually). The user is expected to pay for the software or stop using it after the trial runs out.
Freeware is free to distribute but the creator still owns the copyright so usually one would not be allowed to modify or sell the software.
Public domain software is where the creator has relinquished all rights to the software so anyone can sell, change, give it away as they please. If a software license has expired or a creator wave their copyright privileges then the software becomes available for all.
Open Source or Free and Open Source Software (FOSS) is for users to do however they please with the source code or modifications. Users are encouraged to distribute it for free and with the communities around the world using it, it can be improved by those experts and re-distributed. There are no official help desks or places to turn when the software fails like with commercial software but thats the cost of using free software.
Cloud computing is storing files and applications on a server somewhere on the Internet ('in the cloud'). Content is accessed usually via a browser or by a native app on mobile and tablet. All of the processing and storage is handled by the server online and allows for excellent features such as collaboration on a document by users in different locations at the same time. However, a downside is that the user must have a reliable Internet connection in order to stay connected. Another issue is security as files and data can be accessed via a username and password, it's easier to be hacked.
Command Line Interface (CLI) such as MS-DOS or Terminal where the user uses a keyboard to type in commands, or a Graphical User Interface (GUI - 'goo eee') such as Windows, which is operated typically with a point and click device such as a mouse or track pad. The interface allows users to start and stop programs, switch between running applications and create, copy, move, or delete files.
All software contains bugs which are errors and mistakes made by developers as they write the software. As software becomes more complex, the amount of bugs increases. Bugs can be fixed by developers and then released to users as 'patches'. One particularly famous bug was the 'Millenium Bug'. Read more about it here.