The operating system is the most important system software in a computer. It is the first program that loads when the computer is switched on, and it remains active as long as the computer is running. The operating system acts as a manager of the computer, controlling the hardware, running other programs and providing a friendly way for the user to interact with the machine. Without an operating system, a computer is just a collection of useless electronic parts.
Common examples of operating systems are Microsoft Windows, macOS, Linux, Android and iOS. Each one is designed for a different kind of device: Windows and Linux run on desktops and laptops, macOS runs on Apple computers, and Android and iOS run on smartphones and tablets. This chapter explains what an operating system does, the types of operating systems, how a computer boots, the user interfaces and the important concepts of files and folders.
The operating system performs several essential functions that keep the computer working smoothly. First, it manages the processor and memory. It decides which program uses the CPU at any given time and allocates memory to the running programs so that they do not interfere with one another. This is called process management and memory management. Second, it manages all input and output devices. When we press a key or click the mouse, the operating system receives the input and sends it to the correct program.
Third, the operating system manages files. It organises data into files and folders, helps the user save, copy, move and delete files, and keeps track of where every file is stored on the disk. Fourth, it provides security by allowing users to create passwords and user accounts, and it controls who can access which files. Finally, the operating system provides the user interface, the screen through which we interact with the computer. In this way, the operating system manages every resource of the computer.
Operating systems can be classified according to how many users and tasks they support. A single-user operating system allows only one user to work on the computer at a time, such as a personal computer at home. A multi-user operating system allows several users to use the computer at the same time, each through their own terminal, as in mainframe systems. Similarly, a single-tasking operating system can run only one program at a time, while a multi-tasking operating system can run many programs at once, which is what modern operating systems do.
Operating systems are also classified by their response to time. Real-time operating systems are used in machines that must respond instantly to events, such as in spacecraft, robots and medical equipment. Network operating systems manage the resources of a network and allow sharing of files, printers and internet among connected computers. Some examples are special server operating systems. Each type of operating system is designed to meet the needs of a particular environment, from a simple home PC to a powerful bank server.
Booting is the process of starting the computer. When the power is switched on, the BIOS, which is firmware stored in ROM, runs the Power On Self Test (POST) to check the hardware, and then loads the operating system from the hard disk into the main memory. After booting, the operating system takes control of the computer. There are two types of booting: cold booting, which happens when the computer is started from a completely switched-off state, and warm booting, which happens when the computer is restarted without switching off the power.
The user interface is the part of the operating system that allows the user to communicate with the computer. There are two main types of user interfaces. The Command Line Interface (CLI) requires the user to type commands in text, such as "copy file.txt". It is fast but difficult for beginners. The Graphical User Interface (GUI) uses icons, menus, windows and a mouse, so the user can click on pictures instead of typing commands. Windows, Linux and macOS all provide a GUI, which makes the computer easy to use for everyone.
Data in a computer is stored in files. A file can contain a document, an image, a song or a program, and every file has a name and an extension, such as report.txt, photo.jpg or song.mp3. The extension tells us what type of file it is. A folder, also called a directory, is a container used to organise files. Folders can be placed inside other folders to create a tree-like structure, which helps us keep our work arranged neatly. The main window of Windows shows icons, a taskbar and the desktop.
The Windows operating system provides several useful tools. The desktop is the main screen, and icons are small pictures that represent programs or files. The taskbar at the bottom shows the running programs and the Start button. The Recycle Bin stores deleted files temporarily, so they can be restored if needed. The Control Panel and Settings allow the user to change the appearance and settings of the computer. Understanding these features helps us use the computer efficiently in school and at home.
| Function | What it Does |
|---|---|
| Process management | Decides which program uses the CPU |
| Memory management | Allocates memory to running programs |
| Device management | Controls input and output devices |
| File management | Organises and controls files and folders |
| Security | Manages user accounts and passwords |
| User interface | Provides the screen to interact with the computer |
| Type | Number of Users / Task | Example |
|---|---|---|
| Single-user | One user at a time | Home PC operating system |
| Multi-user | Many users at a time | Mainframe operating system |
| Single-tasking | One program at a time | Old MS-DOS |
| Multi-tasking | Many programs at once | Windows, Linux |
| Real-time | Instant response | Spacecraft and robot systems |
| Network | Manages network resources | Server operating systems |
The operating system is the manager of the entire computer. It controls the processor, memory, devices and files, provides security, and offers a user interface through which we work. Operating systems come in many types, from single-user systems for home computers to multi-user and real-time systems for powerful machines. Understanding booting, user interfaces and file management helps us use the computer confidently. In the next chapters, we will apply this knowledge while learning about applications such as word processing, spreadsheets and presentations.