Lesson video

Hi, my name is Mr. Hall and welcome to this Oak National Academy lesson, which is called Computer Architecture and it's taken from the unit Computer Systems and Data Science.

I'm delighted you've joined me for this lesson today.

So let's get started.

Today's learning outcome is I can describe the parts of a computer system and explain how they work together to execute programmes.

We've got four keywords in this lesson.

The first keyword is processor, and the processor is the part of the computer that carries out instructions and makes decisions.

So that's the processor.

Secondly, we've got random access memory, or RAM.

So random access memory is where the computer temporarily stores data and instructions it's using.

Next we've got storage.

So storage is where the computer keeps data and files permanently, even when it's turned off.

And finally we have execute.

So execute is to carry out a programme or a set of instructions on a computer.

So there's our four keywords or phrases, processor, random access memory or RAM, storage, and execute.

We've got two learning cycles in this lesson.

So the first learning cycle, which we'll start in a minute, is to describe parts of a computer.

And then later in the lesson, you'll move on to explain how a computer executes a programme.

So let's get started with that first learning cycle: describe parts of a computer.

So Laura's got a question for Jun and she's asking, "Do you know what parts all computers have in common?" And Jun says, "Well, there are so many different types of computer, but I think they all must have processor, memory, and storage." So let's see if they're right.

Jun is correct.

All computing systems need a processor, memory, and storage.

So the processor is sometimes called the CPU and the memory is where things are stored when they're being used.

And storage is where things are stored permanently.

Note that computer systems may contain far more components than this depending on their application, but they all do have this in common: processor, memory, and storage.

Sometimes computer parts may be given acronyms or known by different names.

For example, a processor may be called a central processing unit.

This is often shortened to the acronym CPU.

There are also two types of main memory.

So we have one type of memory called random access memory that we've introduced already and that's often shortened to RAM.

The second type of main memory is called read-only memory and is often shortened to ROM.

So two types of memory: RAM and ROM.

And that can get a little bit confusing because they're very similar terms. As a recap, second type of main memory is called read-only memory and is often shortened to ROM.

RAM is the type of temporary memory that stores data and programmes while a computer is in use.

RAM allows the system to work quickly, but its contents are lost when the computer is turned off.

Processes can read from and write to RAM, allowing them to quickly access and store the data needed to run programmes and perform tasks.

ROM is different to RAM because it's permanent memory that stores essential instructions for starting up the computer.

The data in ROM cannot be changed easily and is not lost when the power is turned off.

And Laura says, "I think we forgot to mention the thing that gives all computers the instructions on what to do." Can you think of it? And Jun says, "Oh yes, all computers need a programme that they can execute." All computers need a programme so that they're given the instructions they need to do their work.

And it's a programme that gives those instructions.

And Sam asks, "But a programme isn't a physical part of a computer?" And it's not.

A programme is an important part of a computer system even though it's not a physical part like a processor or RAM.

So a computer system is made up of hardware and software.

Hardware is any component of a computing system that you could physically touch like the processor, RAM, and storage.

Software is the programmes that contain the written instructions to tell the hardware what to do.

Andeep has a question.

"Why do all computers need these parts?" So why do all computers need a processor, RAM, storage, and programmes? Well, each part of a computer system has an important job to do to ensure that the system can work all together.

The processor is the component that executes programme instructions.

An instruction may perform arithmetic or logic operations on data.

It may perform input or output of data.

It might control programme flow.

When you open a game, the processor executes the game's instructions.

When you open a web browser, the processor executes the instructions from the programme.

Whatever programme you open, the processor executes the instructions to make it run.

Time for a question.

Which parts of a computer carries out instructions and makes decisions? Is it A, storage, B, power supply, or C, processor? That's right.

The answer is processor.

So the processor is the part of a computer that carries out instructions and makes decisions.

The RAM is the component that stores the programmes and data currently in use by the processor.

So this is a picture of what a piece of RAM looks like within a computer.

So a computer may contain several of these depending on how much RAM it's running.

So RAM is temporary, fast, and works with the processor.

Remember that RAM is short for random access memory.

When typing a document, the text is stored in RAM while you're working.

RAM is volatile.

This means its contents are lost when the power is off.

So Sam's got a question.

"So what happens when I save my work?" And that's a really good question.

'Cause if RAM is volatile and the contents are lost when the power is off, how do you save your work? When you save your work, the data is moved into storage.

Storage is where a computer saves data and files so they can be used again at another time.

Storage is persistent, which means it retains its content when the power is turned off.

Note that storage devices are generally much slower than RAM.

And on this slide here you've got a picture of a magnetic hard drive, which is a type of storage device.

RAM is built and designed for speed so the processor can work quickly while a programme is running.

Storage is designed to hold large amounts of data but takes longer to access.

There are many types of storage devices.

Can you think of any? Let's look at some examples.

So a USB stick is an example of a storage device.

So is an SD card, which you might find in a camera, a hard disc drive, HDD, a hard disc drive.

That's an example of a storage device.

A solid state drive, which is a different type of hard drive.

That's also an example of a storage device.

And optical discs such as CDs or DVDs are also storage devices.

Time for a question.

Which parts of a computer holds data temporarily? Is it RAM, storage, or processor? Well done.

It's RAM, random access memory that holds data temporarily.

And now a true or false question: storage is where data and files are saved so they can be used again at another time.

Is that true or false? Well done.

That's true.

Storage is where data and files are saved so they can be used again at another time.

Now time for your task.

So match up the parts with the correct description.

So the four parts we've got are processor, storage, programme, and RAM.

And the four descriptions we have is one that temporarily stores important data and instructions when in use, something that executes instructions and processes data.

We've got web data and files are permanently kept even when it's turned off.

And then the set of instructions that tells the computer what tasks to perform.

So match the parts with the descriptions.

Okay, well done.

So first of all, processor executes the instructions and processes data.

Storage is where data and files are permanently kept even when it's turned off.

Programme is the set of instructions that tells the computer what tasks to perform.

And then finally, RAM temporarily stores important data and instructions when in use.

And the second part of your task, in your own words, describe the two differences between storage and RAM.

So this is what you could have written.

One difference is that RAM and storage are designed and used for different purposes.

RAM is used to temporarily hold data that the computer is currently using while storage is used to save data permanently, even when the computer is turned off.

Another difference between RAM and storage is how fast they are.

RAM is designed to work much faster than storage because it needs to quickly supply the processor with the data and instructions it needs to work efficiently.

Let's move on to the second learning cycle, which is to explain how a computer executes a programme.

So Laura says, "I know that the processor executes instructions, but I wonder how it works with other components." A computer follows a cycle of fetching, decoding, and executing instructions stored in RAM to run a programme step by step.

So let's delve into that a bit further.

The fetch-decode-execute cycle describes the basic operation of modern computer systems. To run any programme, the instructions must be fetched, decoded, and executed.

First, instructions are fetched one by one from RAM into the processor along with any data that's needed.

So there's the memory feeding the processor with instructions and data.

The processor decodes and executes each instruction.

When decoding, the processor works out what the instruction means.

Once decoded, the processor executes the instruction.

When all instructions have been executed, any resulting data is moved into memory.

So the process has executed the instructions and the resulting data goes back into the memory.

The fetch-decode-execute cycle is repeated for as long as the computer is running.

So whenever you've got a computer running, this is happening all the time and it's happening really, really quickly all the time.

Note that this is also sometimes referred to as the FDE cycle.

So fetch, decode, execute, FDE.

An analogy can help you remember how the parts of a computer work together as a system to execute a programme.

So let's have a look at one.

Consider how a knitter may knit a jumper.

Knitting patterns, yarn supplies, half finished and finished projects are kept on the shelves, there's the shelves there on the right-hand side of the image, and we could think of those as storage shelves.

This is like the storage for programmes and data.

When the knitter works on a project, the knitting pattern and materials are transferred to the work area where they can be kept handy for quick access.

So there's the work area.

And this is like the RAM where the programme under execution is stored temporarily along with the required data and the processing.

The knitter reads from the knitting pattern one instruction at a time and carries out the instruction operating on the material at hand.

So what do you think that might be representing? So there's the knitter.

And the knitter is like the processor executing the instructions.

Laura says, "Oh, that makes sense.

So the processor fetches instructions from RAM, decodes them to work out what the instruction means, and then executes the instructions and then cycle is repeated." So let's have a look at a question.

What does the F stand for in the FDE cycle? Is it A, format, B, forward, or C, fetch? That's right, it's fetch.

So F stands for fetch in the fetch, decode, execute cycle.

Another question, during the decode phase, the processor, does it A, work out what the instruction means, B, send the resultant data to memory, or C, copies the programme to storage? Well done.

During the decode phase, the processor works out what the instructions mean.

Now part one of your task: match up the stages of the FDE cycle with the correct description.

So the three stages we've got are fetch, decode, and execute.

And the descriptions we have are work out what the instruction means, do what the instruction says, gets the next instruction from RAM.

So match up the terms to the descriptions.

Okay, well done.

So the fetch stage is get the next instructions from RAM, the decode stage is to work out what the instruction means, and then the execute stage is to do what the instruction says.

And the second part of your task, in your own words, explain how a computer executes a programme.

And there's a tip here.

If it helps, you could use an analogy to help explain, for example, how the FDE cycle is similar to a chef cooking a meal.

In your own words, explain how a computer executes a programme.

So just like a recipe tells a chef what steps to follow to make a dish, a programme is a set of instructions that tells a computer what to do.

The processor is like the chef because it reads and follows the instructions step by step to complete a task.

The RAM is like the kitchen counter where ingredients are placed and prepared in a temporary workspace that holds everything a chef needs while following the recipe instructions.

Storage in a computer is like a fridge in a kitchen because it holds data and programmes long term just like a fridge stores food until you're ready to use it.

The chef takes each recipe instruction, understands it, and performs it.

This is similar to how a processor fetches each instruction from RAM, decodes it into something it understands, and then executes the instruction.

After following all the steps, the chef produces a finished meal.

And this is like how a computer produces output after executing a programme.

So here's a summary of this lesson Computer Architecture.

So every computer has the same basic parts such as processor, RAM, and storage.

The central processing unit, or CPU, executes instructions and controls other parts of a computer system.

All computers use the fetch-decode-execute cycle as the basic way they execute programmes.

Thank you very much for joining me for today's Oak Academy lesson.

I hope you enjoyed learning along with me and I look forward to seeing you again in the future.