Original subtitles

Welcome back.

Ladies and gentlemen, to one of your most important and influencing topics in all of your programming

careers.

And in these section, as well as if you decide to study more advanced topics, pointers is something

that will definitely accompany you because it's actually the bases and the core for so many things in

programming as well as that's something that you're probably going to be asked on your C programming

interview questions.

So make sure you watch this topic from start till the end and practice that in the best possible way

you can.

So let's go.

I want us to make a quick reminder of the swab code we've used in one of our previous sections.

We simply wanted to take two variables into swap between their values and the main function.

Right.

So that was something like this.

We created our main function.

We initialized two variables into A equals two five, B equals two, seven and Vand.

To implement this swap operation, we just created another variable called temp.

We assign to temp A equals two, maybe equals 10.

Basically all the swap functionality we implemented in the main function.

It just looked like this.

And now since we already know how functions can be used in what for they are being used, we would like

to take this piece of code from the main function and put it inside some unique function and call these

function.

Just a swap.

OK.

Just to extract it out from the main function because we are already know how functions work.

We know that these swap functionality between two variables may be used more than just once.

Right.

It's usage may be required in many places in our program.

So that's why we would like to take these lines of code responsible for swapping and put them inside

a separate function.

So that now we will have all the responsibilities and all the code for the swap between two numbers

in just one place and not scatter it in many places in the main function.

And also, it will give us the ability to call this function whenever we would like to make some swap

operation.

Okay, so let's see how the code looks like in our C programming example.

And basically we see that we have a function of a volume type, the name of the function, a swap.

It has two values that it gets in one in two.

So we whenever we will call this function, we will give it two values.

One value will be assigned to number one and one value.

The second value will be assigned to number two.

Then what we are going to do is to create a temp variable that will assist us with on the swapping operation.

And we will print out now one before this WAP and NUM, two before the swap made the swap operation

the swap functionality and then print the values of number one and number two once again, just to make

sure that the swap works as expected.

So if we are to run this code right now, we will see on the console application that no one before

swap equals to five and num two equals to seven.

Right.

As expected, because we initialize it in the main function.

And also we will see that after the swap are we have number one equals to seven and number two equals

two five.

Everything works as expected.

So we have this while function, this WAP room that whenever we call this function, it will receive

two values and print them before the actual swap and after.

And this function will print this information on.

That's kind of a downside.

It will bring these information every time, every time we're going to call this function.

Are these two lines two four lines of this?

What are the values before and after will be printed?

And that's basically maybe something that we don't want.

Maybe you will want this one function just to swap between the values without printing them and to leave

maybe the printing onto another function and so on.

So we can say that sometimes we may want it and sometimes we may not want these two lines.

So let's just stick around with this one functionality for now.

Okay.

And let's see what will happen if we use these print lines in the function before and after.

Calling this what function?

Okay.

We will see it right away.

But basically, we we expect that the same result will will be seen on the screen that once on that,

once the swap function is over.

Then the variables in the main function will also be swapped and the messages will be seen on the screen.

Miskelly, what we want to do is not to put the print line.

The swap function, but rather to keep the printing, for example, in the main function, okay.

And swap function will be responsible for just swapping.

So let's try to do this and it will look like this.

Here is our void's swap.

It's responsible for swapping between number one and two.

And there you go.

You have the void main function.

So basically, it brings out the numbers before and after the swap.

And here we can see the function call a swap for A and B, and we just pass the values of A and B and

the are getting inside of number one and number two.

And if we wrong this program right now.

OK.

And you may just copy and run it on your own to see what happens.

You will see that nothing really happened.

It seems that the variables A and B and B were not swapped.

And that's a very important note that you must understand.

So y y basically it's happening, guys, y, A and B remain the same even after the call to this swap

function.

If it's done correctly here.

Right.

It's done basically correctly y of the result.

The printed A and B values seems to be the same, meaning A equals two five before and after the swap.

And it shouldn't be like that.

It should contain the value of B, which in this case is just seven after the swap.

But but it's not what happens.

OK.

Try to run it on your own just to make sure that you see the problem here.

So basically, although off for number one and number two, it seems that they were swapped inside the

swap function.

OK, so now one and two were swapped because they are local to the swap function.

But the actual A and B values, which are in the main function, which are values that we want to swap,

were Nance swap.

That's very interesting and that's the basis.

And one of the first and most important nodes explaining the reason of why you should consider using

pointers as well as what is passing by value and passing by reference that we are going to talk right

now.

So I hope that you are ready.

And in the next video, what we are going to do is that we are going to try and to visualize all of

these situation of this swapping and thoroughly understand what happened here and why it seems that

things were not working as expected.

And also, we are going then to describe and to to learn why we should consider using loops.

And when we should use it and how we should use it.

So don't worry.

This topic is not the easiest one.

But we will cover it.

I think pretty good.

So I'll see in the next video.