 Hi, again, in this lesson, we're going to write our first program in TypeScript. We will write Hello World program first. What we're going to do is to open a new file and let's define a variable. Let's call it Hello and let's put some text. For example, Hello World. So our variable will have string content Hello World. In TypeScript, you must define your variables. So we need to put keyword bar. You don't need to do that in JavaScript. So our variable Hello has string type. So if you want, you could also put after your variable Hello colon and put string to show that your variable has string type. Okay, next, what we want to do is, for example, to set a new content of our body tag into our HTML file, so we could say, for example, document.body.inner.html and set the value of our body's content to have this text from our variable Hello. So our string variable Hello will have this text Hello World and with that text Hello World, we're going to set and update our body content of our HTML file. Next, let's save our file as Hello World.TypeScript, so Hello World.ts. Now what we want to do is to compile our TypeScript file into our JavaScript file, okay. Let's open our comment prompt and let's find the destination of our Hello World TypeScript file. I will navigate through directories to find our file. Here we have it, Hello World.ts and let's compile it to JavaScript. We're going to use command TSC, which stands for TypeScript Compiler and as an argument we're going to put the name of our file, HelloWorld.ts. I will press enter and now we have new created JavaScript file from our TypeScript file. Let's make, for example, an empty HTML file. Let's save it as index.html. Let's put some basic stuffs, basic tags inside it and inside our body tag, let's use our script tag and let's call our Hello World JavaScript, let's save it. So we've made our TypeScript file, we compile it to JavaScript and then we are using that JavaScript file in our HTML document. Now I will find it and open it, let's show it in Explorer and let's open our index.html. Let's open it and here we have text, Hello World. That's all in this lesson, thanks for watching, bye-bye.