 In this video, we are going to learn about the so-called Markdown language. So Markdown is a formatting language that helps us to format text. It has nothing to do with Python, but it is still worthwhile to learn about it because the JupyterLab environment supports it, and the materials that I provide you with, the book materials, they are totally written in the Markdown language, and you will also use it yourself when working on the assignments, so it makes sense to give you a brief introduction on that. So to do that, let's create a new notebook file, and let's rename it into Mastering Markdown, and so now we have started. And now, by default, I get a new cell, and by default, every new cell in a notebook file is always a code cell. So let's go in there and execute the code 1 plus 2, Ctrl-Enter, and we get back to result 3. Now, how could we have seen that this cell is a code cell? Well, if we go into the cell or if we are on the cell, then if we select from this drop-down menu, then we see that the code option is already pre-selected, and there are a couple of other options, most notably the Markdown option. That is what we are going to use in this video, and these two options, Code and Markdown, are the two ones that you will most likely need in this course a whole lot. The other two are not so important. So let's for now go ahead and create a new cell above the current one just by hitting A for above, and as we see by default, we get a code cell again, but now if we choose Markdown, then what we see is, here to the left-hand side of the cell, we see the empty brackets that should hold the execution count number, but if we hit Markdown, then this goes away. So this is how we see that a cell is not a code cell. And if we go into this, we could write something like this. This is text laid out in bold and in italics. So now the question is, if we look at this, well, this text is of course not yet formatted, but as you can see here, I want to make this word, the word bold, I want to make it a pure bold as well. So how do I do that? Well, by simply wrapping it inside a pair of double stars. So double star, the word bold and then double star, this is what makes this word look bold. Similarly, if I want to make the term in italics and put it into a different format, I could wrap it with single stars and this will make the word look italic. Okay, however, if I now go ahead and press the escape button to leave the cell, we see that nothing really happens. So the stars are still there. So let's go back in and let's think about how can we make the formatted text cell formatted cells? Well, this is conceptually quite similar to a code cell being executed. So in other words, I'm now going to hit the control enter key again and execute, so to say, the markdown cell. And then what we see is the text is now nicely formatted and the word bold is in bold and the word italics is shown in italics. Okay, there are a couple of other options as well. So let's look into some of them. Most notably, if you want to write a short notebook file with some nice storyline that you want to write up, then you want to write titles. So how can we do that? Let's go ahead and use the single hashtag sign and the single hashtag is what indicates to mark down that the line is a title line of highest order. Okay, so let's maybe write simply title here, hit control enter again and we see the word title is now formatted as the title of the document. If you want to format a subtitle, what we could do is we simply go ahead and we use two hashtags and two hashtag will create a title of second order, so to say. So it's a little bit smaller as you can tell and we can go further levels down and I think usually you never need more than three or four levels for titles here but you can see that you can nicely format the text here. A couple of other options that you have is we can create unordered lists. So how do we do that? Well, the way to do that is after the line that introduces the list which is not needed really but we put it there to make it look nicer. You simply write a minus sign which is also called a dash and then we can say a bullet point for example. And then we make a second line and a second dash and we will say another bullet point. And if I now go ahead and hit control enter, we see that the bullet points become non-surprisingly bullet points. So that's an unordered list. We could of course also go ahead and create an ordered list. So an ordered list looks like this. First, do this. Second, do that. It's like a recipe. So now the one and the two they are indented here with a little bit of space and this is how Markdown formats an ordered list. We could even go ahead and say here step one, step two and dot, dot, dot. We can even create a nested unordered list inside an ordered list. And of course we could also have ordered this one by saying one dot, two dot, three dot. This would of course also work and now by default Markdown uses ABC instead of numbers. Okay, but other than that, this is how Markdown just looks like in JupyterLab. So what are other options that we have? So I'm not going over every detail here. So I simply will show you a very good write up of what the Markdown language can do and you can look for it for yourself by simply searching for mastering Markdown on the internet. And this will take you to the first third result here to a GitHub page. Let's click on it. And this is an article. It should take you probably 10 to 15 minutes to read and this will show you all the options that you have and Markdown has nothing to do with GitHub with the company GitHub, but GitHub uses it a lot. So that is why they have an article on it. So I will show you one more option. So maybe you want to create a link inside a document. So let's do that here. We can link words to websites. So for example, if I, for example, to link to, let's say Google, what we would do is the following. We would take the word Google, the word for which you want to create a link and put it inside brackets and then following the closing bracket, we follow that with a pair of parentheses. And in there, we will write a link, htps colon double slash www.google.com and now if you render this with control enter, we now have a link on which we can click and this takes us to Google's main search page. Okay. As I said, you should go over Mastery Markdown quite soon. It's not very hard. And this is what I use to lay out the book chapter. So for example, if I go into chapter 0, 0, the first file here, if I double click on the title here, we see it's formatted with a hashtag here. And also you will see an example of how to include images and other things. So that is a nice thing to know. One last thing in this video, if you want to write or if you want to include a code example inside your text, you can also do that. And I do that also quite often. So for example, if I say in Python, 1 plus 2 is 3 and I format this, then the 1 plus 2 is 3 is simply just black text on white background. But if I want to format this to look like code, what we will do is we will wrap these parts with so-called back ticks on the American keyboard. You will find the back tick next to your escape key. And by wrapping the numbers and the expressions here inside back ticks, what happens is when we format a text, this piece has now a gray background and is also monospaced. So this looks like the code below. And this is also something that I use quite heavily when I prepare these videos, but also of course in the book materials. So this is what Markdown is. And maybe one last thing that I didn't mention yet. Let's say you have a code cell and you want to make this cell a Markdown cell and you don't want to use the mouse. What you could do is you first press escape to leave the cell and then you simply press M, M for Markdown and this transforms the code cell into a Markdown cell. This is the keyboard shortcut. And the other way around is the button Y. So if you press Y, this transforms a Markdown cell into a code cell. And then of course we can rerun the code cell. So that is Markdown. So please learn a little bit about that and then I'll see you in the next video where we start to learn about the Python language.