By the end of this lesson you will be able to
- Explain the operating system's role between hardware and applications.
- Name the main jobs an operating system performs.
- Compare Windows, Ubuntu (Linux) and macOS at a high level.
- Explain what a desktop environment such as GNOME is.
- Tell an application from a process and find the running processes on your own computer.
You have already met the operating system as the thing that loads when a computer starts. Now we look at what it does all day. It is the quiet manager that lets many programs share one set of hardware without crashing into each other. Understanding this makes updates, drivers, permissions and error messages in later lessons much easier to follow.
The manager in the middle
Imagine a busy restaurant. The customers are your applications, each wanting something. The kitchen equipment is the hardware: processor, memory, storage, screen. If every customer wandered into the kitchen and grabbed what they liked, there would be chaos. A restaurant manager takes orders, decides who gets which cooker and when, and keeps things safe. The operating system (OS) is that manager.
Programs do not talk to hardware directly. An application such as a browser asks the operating system to read a file, draw on the screen or send data over Wi-Fi. The operating system passes the request to the right hardware and brings back the result. That is why the same browser can run on laptops with very different parts.
You are here
Read this figure as text
A stack of layers from you at the top, through applications, the operating system and drivers, down to hardware.
Four layers from top to bottom. At the top, you, using the screen, keyboard and mouse. Second, applications such as a browser, a word processor and a music player. Third, the operating system, made of the kernel, drivers and the desktop. At the bottom, the hardware: processor, memory, storage, display and network card. Requests go down the stack and results come back up. Applications never touch the hardware directly.
The jobs an operating system does
At the centre of the operating system is the kernel. It is the part that has full control of the hardware and does most of the managing. Around it sit drivers, system services and the desktop you see. Together they do six main jobs.
| Job | What it means | Everyday example |
|---|---|---|
| Running programs | Starts, pauses and stops programs, and gives each a fair share of the processor. | Your browser and music player both seem to run at once. |
| Managing memory | Decides which program may use which part of RAM, and keeps them apart. | A crash in one program does not wipe out another. |
| Managing files | Stores, names, finds and protects files on the drive. | Saving a letter into Documents. |
| Talking to hardware | Uses drivers to speak to the screen, printer, Wi-Fi and so on. | Plugging in a printer and printing. |
| Security and accounts | Decides who may log in and who may change what. | Your password and your private files. |
| The interface | Gives you windows, icons, menus and settings to use. | The desktop, the taskbar or the dock. |
Sharing the computer's resources between programs is called resource management. The processor is shared by switching between programs so quickly, many times each second, that it looks as though they all run together. The OS also protects programs from each other, so a badly behaved one cannot overwrite another one's memory.
- Run programsShares the processor
- Manage memoryKeeps programs apart
- Manage filesStores and finds them
- Talk to hardwareThrough drivers
- SecurityAccounts and permissions
- InterfaceWindows and menus
Read this figure as text
Six icon cards naming the jobs of an operating system.
Six cards. Running programs: gives each program a turn on the processor. Managing memory: keeps programs apart in RAM. Managing files: stores and finds your files. Talking to hardware: uses drivers for screen, printer and network. Security and accounts: checks who you are and what you may do. The interface: windows, icons and menus you use.
Windows, Ubuntu and macOS
Three families of operating system are most common on personal computers. Windows, made by Microsoft, runs on a huge range of laptops and desktops and is used in many workplaces and schools. macOS, made by Apple, runs only on Apple's own computers. Linux is not one product but a family built around the Linux kernel, which is open source, meaning anyone may read and share its code. Ubuntu is a popular version of Linux, called a distribution, and is the one on your laptop.
Phones use the same ideas: Android is built on Linux, and iPhones run iOS, which shares roots with macOS. The look differs but all of them do the six jobs.
- Runs on many makers' laptops
- Huge range of programs
- Licence is paid for, usually included with the computer
Most common in workplaces.
- Free and open source
- Runs on ordinary laptops
- Updates are free
Your current system.
- Only on Apple computers
- Hardware and software made together
- Free updates
Polished but tied to Apple.
Read this figure as text
Three columns comparing Windows, Ubuntu Linux and macOS.
Windows: made by Microsoft, found on a very wide range of laptops and desktops, strong software choice for business and games, mostly paid for as part of the computer. Ubuntu Linux: a free, open-source distribution maintained by Canonical and a community, runs on ordinary laptops, uses the GNOME desktop, and gets updates free. macOS: made by Apple, only runs on Apple computers, closely tied to its hardware.
The desktop you see is part of the system
The windows, panels, menus and icons you click are drawn by a desktop environment. On Windows the desktop is built in. On Linux you can choose one. Ubuntu uses GNOME by default, which gives you the Activities button, the dock and the system menu you met in the first module. Other Linux versions use different desktops, so they look different while running on the same kernel. That is also why a tutorial written for another Linux version may show a different screen from yours.
Applications and processes
An application is a program installed on the computer, sitting in storage. When you open it, the operating system creates a process: a running copy that has its own memory and a share of the processor. Close the app and the process ends. You can open the same application twice and get two processes. A big app such as a browser may even start many processes at once, one per tab, to keep the tabs from affecting each other.
- Step 1: Stored applicationA file on the drive
- Step 2: OpenedOS creates a process in RAM
- Step 3: Opened againA second, separate process
- Step 4: ClosedThat process ends; the file stays
Read this figure as text
A flow from an application file on disk to two running processes in memory.
Step 1: an application sits on the drive as a file and does nothing. Step 2: you open it, and the operating system loads it and creates a process in memory. Step 3: you open it again and a second process starts, from the same stored application. Step 4: you close one window and only that process ends; the application is still stored on the drive.
See the running processes
Ubuntu: System Monitor
Step 1: Open System Monitor
Open Activities, type
System Monitorand press Enter.You should see: A window opens with tabs named Processes, Resources and File Systems.
Step 2: Look at the Processes tab
Click the Processes tab and look at the list. Click the heading of the memory column.
You should see: The list reorders so the processes using the most memory come first or last.
Step 3: Look, do not end anything
Just read the names and sizes. Do not end any process you do not recognise.
You should see: You can name one process that is your browser or file manager.
Windows: Task Manager
Step 1: Open Task Manager
Press Ctrl + Shift + Esc, or right-click Start and choose Task Manager.
You should see: A window opens, normally showing the Processes page.
Step 2: Look at the list
Find the group called Apps, then Background processes below it. Click the Memory heading.
You should see: The list reorders by memory use.
Step 3: Look, do not end anything
Read the names. Do not click End task on anything you did not open yourself.
You should see: You can name one entry that is your browser or File Explorer.
- Marker 1: Apps you opened yourself
- Marker 2: Background services the system started: leave alone
Read this figure as text
A simulated monitor window listing a browser, a file manager and background system services with memory sizes.
A simulated window titled Process monitor with a list. Row 1: Web browser, using 640 MB of memory, marked as an app you opened. Row 2: Files, using 90 MB, also an app you opened. Row 3: Network service, using 25 MB, a background process the system started. Row 4: Sound service, using 18 MB, a background process. Markers: 1 points to the app rows, which you started yourself; 2 points to the background service rows, which the system started and which you should leave alone.
Common mistakes
✖ Instead of: Thinking that Linux and Ubuntu are two competing systems.
✔ Do this: Linux is the kernel and the family built on it. Ubuntu is one version, or distribution, of that family.
✖ Instead of: Ending unfamiliar processes in Task Manager or System Monitor to make the computer faster.
✔ Do this: Many are background services the system needs. Close only apps you opened. Restart if the computer is slow.
✖ Instead of: Believing the desktop and the operating system are the same thing.
✔ Do this: The desktop environment is the part you see and click. It sits on top of the kernel and drivers.
If something goes wrong
- System Monitor is not in my Activities search.
- Type
monitorinstead and look for System Monitor. If it is missing, open App Center and search for it. Do not worry, it is not essential for daily use. - Task Manager opens as a tiny window with only app names.
- Click More details at the bottom-left. Then the full list with tabs appears.
- I see hundreds of processes and feel overwhelmed.
- Look only at the Apps group, or sort by memory and read the top few. Ignore the rest. They are mostly system services.
Key terms
- Operating system
- The main software that runs the computer and lets you and your apps use its parts.
- Kernel
- The core part of an operating system that manages the hardware and runs everything else.
- GNOME
- The desktop environment Ubuntu uses by default: the panels, dock, menus and windows you see and click.
- Resource management
- The operating system's job of sharing the processor, memory, storage and devices fairly between all running programs.
- Process
- A program that is currently running, together with the memory and resources it is using.
- Desktop environment
- The part of an operating system that gives you the screen, windows, menus and icons you click.
Practise it for real
Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.
Name the layers and find your processes
Open System Monitor (Ubuntu) or Task Manager (Windows). Open your browser and a file manager. In the list, find both programs and note how much memory each is using. Then, from memory and without looking at the lesson, draw the four-layer stack of you, applications, operating system and hardware and write one example in each layer from your own laptop.
Challenge: explain the manager
Without notes, explain to someone what an operating system does using your own comparison instead of the restaurant. Include at least four of the six jobs and say which operating system and desktop your laptop uses. Then ask them to tell you the difference between an application and a process.
Knowledge check
6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.
Summary
- The operating system manages hardware and lets applications share it safely.
- Its six jobs: run programs, manage memory, manage files, talk to hardware, handle security, provide the interface.
- Windows, Ubuntu (Linux) and macOS are three families that all do these jobs.
- A desktop environment such as GNOME is the part you see; the kernel is the core underneath.
- An application is stored; a process is a running copy of it.
Checklist: can you do these?
Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).
Related lessons
References and further reading
Official sources for details that can change between versions.
- Ubuntu Desktop help (Ubuntu)
- What is Ubuntu? (Canonical)
- Windows help and learning (Microsoft)