Lesson video

Hi, my name's Mr. Hall, and welcome to this Oak National Academy lesson, which is called "The operating system," and it's taken from the unit, "Computer systems and data science." Thank you for joining me for this lesson, and I look forward to learning with you today.

The outcome of this lesson is "I can explain how operating systems control computers and manage resources." So let's get started.

We have three keywords in this lesson.

So the first keyword is control, and control means to manage or direct the behaviour of a system or process.

So that's control.

Then we have operating system or OS for short.

The main software that manages computer resources.

That's operating system or OS.

And finally, hardware.

So hardware is the physical parts of a computer that you can see and touch.

That's hardware.

So there's our three keywords, control operating system or OS, and hardware.

We have two learning cycles in this lesson.

So first, you're going to define an operating system, and then later in the lesson we'll move on to explain how an operating system manages resources.

So let's get started with the first learning cycle, define an operating system.

So Andeep has a question for Jun.

"Do you know how many programmes can be executed at the same time?" And Jun says, "Well, I remember a processor can only execute one instruction at a time.

So I think it's one." Let's see if he's correct.

He is, and we'll look at why now.

At any given time, a single core processor executes one instruction that is part of one programme.

So one processor, one instruction, one programme.

But Laura says, "But I often have lots of programmes open at the same time.

How does that work?" So there's an example.

You can see there's at least four programmes open on that desktop.

There may even be more open that you can't see.

So several programmes open at the same time.

So if a single processor can execute one instruction, one programme, how can we run multiple programmes at once? So let's have a look.

So a single processor can be made to alternate between executing the instructions of different programmes.

This makes it look like multiple programmes are being executed at the same time, but actually, the processor is still only executing one programme at a time.

So it's very quickly switching between those programmes, but only ever executing one instruction per programme at any one time.

A single core processor that switches between executing programmes is similar to how a single builder can only work on one wall at a time, but could quickly switch between building different walls.

So we have four walls being built, but they can only be built one at a time.

Currently the speed, so that's the clock ticks per second, is at 1.

So each wall is being built with one instruction happening per second.

I can increase the speed slightly.

So if I go to 6 ticks, you can see that still, there's four walls being built.

It's still only one instruction per time, but it's happening quicker.

And I can go right up to a really fast speed, say 92, and you can see that it's still four walls, one instruction per time, but much quicker because the clock speed is quicker.

So have a look at that simulation and that gives you an idea of how a processor can manage one instruction for one programme at any one time.

But the faster the processor, the more instructions it will be able to handle.

So Andeep has another question now, "But what happens if a processor has multiple cores?" In that case, each core can execute instructions from a different programme.

In the brick building analogy, this is like having multiple workers building a wall each, so it'd be a quicker process.

So there you see, we have potentially four bricklayers each building their own wall.

So you can see that would be four times as fast as a single processor if they were all working at the same speed.

So Andeep says, "So the processor executes the programme instructions, but what controls the processor, which is a really good question.

And Jun asked, "And what controls were the programmes and data are stored in the RAM?" And the answer to both those questions is the operating system is the main software that controls how a computer works.

So let's have a look at the operating system in a bit more detail.

There are several very well-known operating systems that are installed on different devices like laptops, tablets, and phones.

Can you think of any operating systems that start up when you turn on a computer or a phone? So here's some common ones that you may have come across.

So the first logo is for the Android operating system, which typically you'll see on phones and mobile devices.

Then we have OS, which is Apple's operating system.

So you'll typically see that on Apple devices.

And then finally, Windows on the right-hand side, which you will see on desktop PCs and laptop PCs.

The operating system is the first software that loads when a computer starts and serves as a base for launching and running applications.

The main purpose of an operating system is to allow users and applications to interact with and control computers and its hardware.

The operating system controls the computer's hardware by acting as a bridge between the physical components and the software, allowing them to work together effectively.

It controls key parts of the computer's hardware such as the processor, RAM, storage devices, and input, output, and peripheral devices.

So there's a lot of work for the operating system to do to make sure all these different components can work effectively together.

Sam says, "Without an operating system, you wouldn't be able to launch a programme." Not only that, you wouldn't even be able to type, click, or view files.

So you wouldn't be able to use your keyboard, you wouldn't be able to use your mouse, and you wouldn't be able to open anything.

Nothing would work.

The operating system also provides the graphical user interface, and this is often shortened to GUI, for the G, the U, and the I, so GUI.

A GUI allows users to interact with the computer through visual elements like Windows, icons, buttons, and menus instead of typing commands.

A GUI makes it easier for most users to control and use the computer.

So before GUIs were around, you had to type everything in terms of commands just on a single line without any graphics, icons, Windows, or buttons to help you.

So GUIs are really useful to make computers easier to control.

So let's have a look at an analogy now.

An operating system is a bit like the conductor in an orchestra.

Just as a conductor cues the musicians, the operating system controls programmes and devices so everything runs smoothly.

In an orchestra, a conductor controls the tempo and tells instruments when to play.

This is similar to an operating system that controls when and how different programmes and devices operate.

Another thing a conductor does is to communicate the musical vision to the orchestra.

In a similar way, the operating system acts as a messenger between the user and the computer's hardware.

So if an update is required, the operating system will tell the user that that needs to happen.

Time for a question.

What is the main software that controls how a computer works? Is it A, the random access memory or RAM? Is it B, the graphical user interface or GUI? Or is it C, the operating system or OS? Well done.

The answer is C, it's the operating system that controls how a computer works.

Now, time for a true or false question.

Every computer runs the same operating system.

Is that true or false? Well done.

It's false.

Can you explain why? And it's false because there are many different operating systems that can be installed on different devices like laptops, tablets, and phones.

And we saw examples of three, so Android, OS, and Windows.

Some of those are some of the most commonly used operating systems. Now, time for your task.

First, in your own words, write one or two sentences to describe what an operating system is, and then state two reasons why an operating system is important for using a computer.

Okay, so the answer to the first question in your own words, write one or two sentences to describe what an operating system is, you could have written something like this.

"The operating system is the main software that controls how a computer works.

It is the first software that loads when a computer starts and serves as a base for launching, and running applications, and controlling hardware." And for the second part of the task, state two reasons why an operating system is important for using a computer, and you could have written something like this.

"An operating system is important because it controls programmes, hardware, and devices so that everything runs smoothly as a system." Another reason is that the operating system provides a graphical user interface or GUI, which makes it easier for users to control and use the computer through visual elements like icons, buttons, and menus.

Now, it is time to move on to the second learning cycle, which is to explain how an operating system manages resources.

Sam asks, "How is an operating system like traffic lights?" Let's have a look.

An operating system is like traffic lights because it controls the flow of data and instructions.

This is similar to how traffic lights control which cars move to prevent crashes and confusion.

So at a junction, if one light is red and the other is green, then only one line of traffic can move.

And by stopping the other line of traffic, you stop crashes and confusion where two lines of traffic might cross.

So that's how traffic lights help to control traffic in a similar way to the way an operating system controls the flow of data and instructions on a computer.

The operating system directly manages a number of computer resources such as the random access memory, the processor time, input/output devices, and ensures all running programmes get the resources they need without crashing or interfering with each other.

So it has a crucial role in the running of the computer.

The operating system manages memory by keeping track of where each program's data is stored in RAM.

And Sam says, "This ensures that programmes do not interfere with each other's allocation of RAM space." Without memory management, programmes could override each other's data leading to crashes, errors, or lost information.

The operating system manages processor time by deciding which programmes or tasks get to use the CPU and for how long.

And Jun is helpfully reminding us that a single core processor can only execute a single instruction at a time for a single programme.

So the operating system manages which programme the CPU will be handling at any one time.

By allocating individual processor time to programmes, the computer can appear to run multiple applications smoothly without freezing or crashing.

If the operating system didn't control CPU time, programmes could try and use the processor at the same time and that would cause conflicts.

The computer might freeze or become very slow because the CPU wouldn't know which tasks to focus on or when.

And sometimes you may have seen computers crashing or blue screening, as you can see on the picture there, and this could be because there's some kind of conflict within the CPU, so it doesn't always work perfectly.

The operating system manages input and output devices by controlling how data is sent to and received from devices such as keyboards, mice, printers, and monitors.

It coordinates communication between the hardware devices and the software.

If an operating system didn't manage input and output devices, programmes wouldn't know how to send or receive data from hardware.

And this could lead to all sorts of problems. It could mean input going to the wrong programme.

It could mean output not showing up correctly.

And it could lead to conflicts between programmes trying to use the same device at once.

Operating systems are similar to traffic lights because they control the flow of tasks in a computer, just like how traffic lights control the flow of traffic.

They both give clear signals to decide who goes prevent collisions by organising movement and aim to keep everything running smoothly and safely.

And just like traffic in the real world, it can only manage so much traffic.

If there's too much traffic for the operating system to handle, it will slow down.

Just as at a junction, if there's too much traffic for the capacity of the road, then the traffic will slow down as well.

Here's a true or false question.

The operating system only controls the internal computer hardware such as the processor and RAM.

Is that true or false? It's false.

Well done.

Can you explain your answer? The operating system also manages input and output devices by controlling how data is sent to and received from devices like keyboards, mice, printers, and screens.

Another true or false question.

The operating system enables a processor to execute multiple instructions at the same time.

Is that true or false? That's right.

It's false.

Again, can you explain your answer? So if you remember right back to the beginning of this lesson, by allocating individual processor time to programmes, the operating system allows computers to appear as if they are running multiple programmes at once without freezing or crashing.

In reality, the processor still executes only one instruction at a time, but it switches between tasks very quickly.

And now time for your task.

In your own words, explain how the operating system manages the following computer resources.

A, the memory or RAM, B, the processor time, that's the CPU time, or C, input/output devices like a keyboard, monitor, and printer.

Okay, so in your own words, explain how the operating system manages the following computer resources, so the RAM memory.

You could have written something like this.

"The operating system manages memory by keeping track of where each program's data is stored in RAM.

It makes sure that programmes don't use each other's memory space and that each one gets the memory it needs.

And now for the processor, so the CPU processor time.

The operating system controls which programmes use the processor and for how long.

It quickly switches between the tasks so that multiple programmes can run smoothly, even though the processor can only handle one instruction at a time.

And finally, input/output devices such as keyboard, monitor, and printer.

The operating system manages input and output devices by making sure the right programme gets the right data.

For example, when you type, the operating system sends your keystrokes to the correct window, and it also controls how things are shown on the monitor or sent to the printer.

So let's have a look at a summary of this lesson, which was called, "The operating system." The operating system is the main software that controls how a computer works.

The operating system is the first software that loads when a computer starts, and serves as a base for launching and running applications.

The operating system directly manages and controls computer hardware, such as the processor, RAM, and input/output devices.

Thank you for joining me for this Oak National Academy lesson.

I hope you've enjoyed learning along with me, and I look forward to seeing you again very soon.