Original subtitles

So functions are.

If you've ever heard the term functions, chances are you probably had some bad dreams about it.

Usually students find this term hard to grasp at first or second or ever.

They usually do not thoroughly understand this topic, but somehow managed to move on.

And since in programming, we have a lot of things related to one another.

Students who act the understanding of the functions topic tend to fill these gaps in their knowledge,

and they will feel difficulties with most of the topics that will follow afterward.

That's why I recommend and I think it's better to learn it once and learn it well and only then.

Once you've done it, you are allowed to proceed to more advanced sections and sections that you are

going to use functions in your programming language.

So in this section, the goal is to do our best to understand what are these functions?

Where do they come from?

Why do we need them for?

And why shouldn't we be so afraid of them?

I will try to give you an overview of real life situations that resemble in somewhat to how functions

are being used in programming.

And only once you get a hold of why we may be interested in using functions in general only then you

may consider moving on to use functions as part of your code in your programming language.

So here we go.

Grab a cup of your favorite drink, take a comfortable posture and let's go.

So I want you guys to think about a situation where we have Bob trying to develop his own newest and

coolest application that should address students needs and show them important information regarding

their grades.

So we can see here, Bob and Bob is there all alone in this story.

And he's trying trying his best to build this application.

But there are so many aspects that Bob needs to take care of, like getting grades from the users,

calculating every student's grade, printing every user's information to the screen.

And there is a lot of other students and there is a lot of students.

There is a lot of things that Bob has to do.

So why am I saying that?

What?

Why do I even say that?

Bob has a lot of things to do and there is a lot of students and so on and so forth.

Basically, what I want you to do in this example is that I want you to think of Bob as the main function,

the main block we've used in the course all along.

So on one hand, it seems like Bob could take care of all these aspects by on his own and all the code

of getting grades, calculating the average grade and so on.

All of that is going to be under the main block.

Just write down a bunch.

A very large bunch of code in the main section and help that this program will work.

So that's pretty much what we are.

We're used to doing all the exercises so far.

Right.

We simply gave Bob to take care of everything because we said, like in this analogy, that Bob is just

like our main function.

Okay.

But the main question that should be asked here is whether this approach is correct or wrong.

Writing all the code under the main section is probably going to be very tedious.

And not only that, but we will also be able to see that there are many repetitive operations that we

do.

For example, calculating every student's grade or printing every user's information should be pretty

much the same for all users.

Right.

And I mean, it's it's kind of obvious that there is a lot of commands that are going on over and over

again, and they are pretty much the same.

So why should we inflate our program with a lot of repetitive lines of code?

It simply doesn't make any sense.

And also, if sometimes in the future, once you release your program, if you will have some bug and

that may happen, how will you track the bug?

There is only Bob.

And you should go over all of his commands, probably line by line and try to track down where is the

problem.

So that's also another reason why you shouldn't leave all the code in just Bob's hands.

That's why it shouldn't be only in one main section.

So for these reasons we've just mentioned so far and for many reasons, we are going to mention also

later on, for these reasons, we decided that we are going to use functions if we know that the process

of calculating the average grade for every student is pretty much the same.

Then we would like to create some guy, let's call him Mike for this example, that his goal is, for

example, to be in charge of getting some grades from Bob and calculating the average grade between

them.

So all these guy, all this Mike knows to do is simply to receive a.

Full of grades and then calculate the average grade and finally return the result to Bob in this example,

meaning that if we have to calculate the average grade for 10 people, then the calculation process

is going to be the same for all of them.

Right.

Mike will just sum up all the grades he has been given and then divide the sum by the total number of

grades.

That's how you'd calculate an average grade.

So we can say that Mike will be in charge just of this task.

Only he will not read inputs from the user and he will not print anything to the screen.

He's here just to help Bob to accomplish everything he needs to get started, to get calculate, to

get his program on track.

Bob will give Mike the grades of some user user one, for example, and then Mike will only calculate

the average grade and return the results to Bob.

That's all Mike will do.

Bob calls Mike and gives him a couple of grades.

Mike finds out the average and returns to Bob.

That's it.

So once again, if there is some repetitive process of doing almost the same task over and over again,

we would like to use some skilled person for doing these kind of tasks.

So for the overall task that we specified previously, there will be a couple of specialists.

The first one knows how to print a greeting message to the to the screen and on the second one knows

how to calculate the average grade.

That's our mike.

And the third one will know we'll be capable of printing the average grade nudge, calculating the average

grade, but printing the average grade through the screen and so on.

So there may be a lot of people with a lot of specialties that will help Bob to organize his application

correctly and for every part of the task.

Bob may ask for the help of any of them.

Ask from their first guy.

For example, to print a nice, good looking girl reading message through the screen to every user.

And Mike will calculate the average grade.

And Steve will print this rate.

But Bob will not be in charge of all of the code inside of some main block.

It will be divided to specialists, to some functions.