 Here we are in lesson 2 and we're going to look at types. We in Julia box We in the folder that we created to put our lesson files in You can either download this file which I'll make available or you can just say new and Create a new Julia notebook. So let's go into types, which is our second lesson Once again, remember these are all cells if I double-click in the cell first of all you can see it is a marked down cell and I've marked it as a heading one the largest Type that can be a displayed in HTML code there We'll look at the second cell there my two little hashtags there two little pound signs Indicating this this is a heading to Introduction so types variable types Now I've written a few things yet. Let's just go through them. Remember just as in Mathematics we have numerical values and they are the certain type if I just have the value 3 I could call that an integer If I have a value 3 over 4 this fraction I can call that a rational number 0.75 now the computer variables can also hold different types That's how a computer language is structured now. Remember it's actually the object that's inside of the variable that has the type But we'll get to that in Computer jargon specifically in Julia these things are also called types Now every time we create a variable That variable holds something and that something is of a type say for instance We were to say x equals 3 then the name of the variable is x and it holds an Integer value, which is 3 in this instance Now this value that it holds is called an object in in Julia and all Everything that's held inside of of of variables in Julius are objects Now Julia has a dynamic type system. What does that mean? It means you don't have to explicitly declare a data type when you create a variable Now in languages with what we call a static type system You will have to do something like this this comes from a different programming language I would have to say integer x equals 3 and this semicolon to end that line of code So I would have to declare that this variable is going to hold objects that are of an integer value And here I've assigned the one up one such object, and I called it 3 you don't have to do that in Julia although you can if you wanted to you can declare a type and Sometimes this is quite good to do because it When you declare type it holds that specific area in your computer's memory And it makes for quite a bit of faster code execution now the types that are available in Julia are Formed in a hierarchical structure structure, and that's what we're going to have a look at next