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Welcome.

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In this lecture, we're going to explore a fundamental programming concept known as variables.

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A variable is a container or a labeled storage box that can hold different values like numbers, text,

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and more complex data structures.

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Variables are used to store and manipulate data within your game, and this data can be retrieved whenever

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you'd like.

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Variables have an identifier, such as a name and a value associated with that identifier.

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A great analogy for a variable is a mailbox.

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You can think of a mailbox like a variable because it has an address or an identifier, and that mailbox

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can hold different items, which would be your values.

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Just like you can put letters, packages, and other items into a mailbox and retrieve them when needed.

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In programming, you can store various types of data in a variable and access that data later on by

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referring to that variable's name.

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So to create a variable, the first thing we need to do is type out the name or identifier for the variable.

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In this case, we can call our first variable something like my first var.

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This is going to be acting as our identifier or name for the variable, and then to store a value or

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associate a value with this identifier, we need to use one equal sign.

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The equal sign is known as an assignment operator.

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In Lua, we are associating or assigning a value with the identifier.

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And as an example, what I'm going to store in this variable is going to be the number like ten.

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So now here we are.

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We have our variable called my first var and it stores the value of ten somewhere in our computer's

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memory.

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Now we can store a lot more than just numbers inside of our variables.

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By default, Lua has seven basic data types that you can store inside of your variables.

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These data types are numbers, strings, booleans, functions, tables, threads, and nil.

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Now again, numbers can be anything from negative to positive, whole or decimal.

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Any whole numbers.

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We like to call them integers.

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So as an example ten.

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Here would be an integer.

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And any numbers that have decimals are called floating point numbers or float for short.

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So for example, if I put a dot here and then put a zero, this would now be considered a floating point

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number.

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The reason we call them floating point numbers is because the decimal point that describes the fraction

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of the number is able to float around or change to represent a different number.

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For example, if we had a number like 3.14, this could be changed into something like 31.4, or we

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could do 0.31 for the decimal point can shift or float around.

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Now strings like we talked about previously are any text between quotation marks.

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We can use strings to do things like share messages to players, make announcements in our game, run

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a countdown timer, and much more.

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So whenever you want to work with text in your scripts, you need to place that text between quotation

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marks to denote it as a string.

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Data type.

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So if I wanted to say something like hello, I would put my quotation marks here and type in hello.

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And now my variable is storing a string data type.

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Next is a boolean.

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And a boolean is a very simple data type that represents two possible values, either true or false.

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Boolean values.

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Let our computers make decisions based on a condition.

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For example, we can check if a player has VIP and if they do have VIP, we can give them some extra

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goodies associated with that VIP.

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So in my first var, I can store a value like false by just typing out false or typing out something

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like true.

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That is our boolean data type.

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Now functions which we will go over later are stored in variables as well.

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They have an identifier and you can refer to this identifier and basically call the function to have

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it execute.

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Code functions are simply blocks of code that perform a specific task.

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And as I said, we will take a look at them more closely later.

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Now a table is another data type and they are created by using curly brackets.

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So up here if I put two curly brackets I have now created a table data type and this table is currently

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empty.

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Tables can be used to store many different values and they can even represent different data structures.

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We will be going over tables later in the course, so I wouldn't worry too much about them for now.

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The next data type is known as a thread, and a thread is created by something in Lua called a coroutine.

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Once more.

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We do not need to worry about this data type for now either.

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The last, but definitely not the least data type is nil.

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This is a special value that represents the absence of a value or the concept of nothing in programming,

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so we use Nil to indicate that a variable does not currently have any assigned value.

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So up here, if I set my first var equal to nil, I'm basically saying that my first var has no.

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Value at all.

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It hasn't been initialized with anything, so nil represents the absence of a value.

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Now the next thing I'm going to quickly note is that you may be wondering why all of this text inside

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of my scripts is grayed out.

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And this is because these are comments, which is for me and other people to read and not the computer.

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If you want to make a comment, you can do so very easily by just putting two dashes before any text.

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So right here, when I type out something like hello there, the interpreter is trying to read this

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as code.

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And because this is not code, we're getting an error here.

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But if I put two dashes before it now I have created a comment and this is just there to help you make

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notes inside of your code.

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Maybe there's an area that might be a little confusing and you want to clarify.

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You put comments in there to make it easier to understand.

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We are also able to make multi-line comments as shown right here.

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And the way to make a multi-line comment is you first go, you put two dashes and then you go ahead

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and put two of these brackets.

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And this creates a multi-line comment.

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We can also do the same thing with strings.

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So if you don't want to use quotations you can use those two brackets.

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And now we can create a string that expands over multiple different lines.

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So this is a multi-line string.

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So if we try to do this with quotation marks it's obviously not going to work.

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As you can see we're getting a bunch of red underlines here because we have to do it with two brackets

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for multi-line strings.

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Now another thing I want to mention with variables are the names that we have given them.

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You want to make sure that the names you give to your variables are descriptive, so you can understand

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what the value inside of them is supposed to represent.

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Traditionally, we name variables using the camel case naming convention.

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This means that the first letter in the first word of your variable is lowercase, while every other

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word after your first word starts with an uppercase letter.

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This is the camel case naming convention.

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Now, you can also not name your variables starting with numbers.

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So if I try to put a one here, we're going to get an error because we cannot name our variables starting

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with numbers.

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We also cannot name our variables with the keywords that are reserved in Lua.

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So for example, one keyword that is reserved in Lua would be something like if and.

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As you can see, we're getting a big red error here because we cannot override this default keyword

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in Lua as a variable.

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If we made it into something like if like or something like that, then it works just fine.

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But we cannot override the defaults.

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Uh, but we cannot override the default keywords that are in the Lua language.

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Now, you might be wondering why do we name our variables with this weird camel case?

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Well, the reason we do this is to differentiate things from being a variable, a class, or whatever

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else camel case is a commonly used naming convention in Lua programming, and some other commonly used

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naming conventions is something known as snake case.

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So if I go down here, we have different other naming conventions that are commonly used.

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So here is our camel case my first var.

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There's also something known as snake case which is popularly used in the Python programming languages.

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And then we also have something known as Pascal case.

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So you can see the differences between these three different naming conventions.

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Pascal case has the first letter capitalized.

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Snake case has them all lowercase with an underscore separating them, and then camel case starts with

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a lowercase and continues on with capitalized letters.

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We typically use Pascal case when we give variable names for classes or something called enums.

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Snake case basically has the same principle as camel case.

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We use them for variables and stuff like that, but most commonly you'll be using camel case in Lua.

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We can also use snake case in another way by capitalizing all of the letters in snake case.

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So if we do something like this, my first var, then this variable name right here is actually representing

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a constant or a value that should never change during the runtime of your game.

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So if you want to define some particular constants in your game or values you never want to change,

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then you would want to do it by using capitals and then underscores to separate the different words

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from each other.

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I'm also going to scroll up here and give you another look at some valid and invalid variable names.

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So again, we cannot name our variables starting with numbers.

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We cannot use any of the reserved keywords in Lua.

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And we can also not use special characters that are reserved in Lua as well.

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We can't use exclamation marks, we can't use multiplication symbols or the and symbol, stuff like

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that.

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These are invalid variable names that are not going to work, but you can go ahead and use these variable

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names.

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These work just fine.

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Now one last thing I want to mention is that variable names are case sensitive in Lua, meaning that

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I could have two variables with the exact same words like these ones here below.

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But I can have different capitalization between these two names.

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And because there's different capitalization, that actually means these two variable names are completely

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different.

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These two variables would reference different places in memory, and they're not the same.

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So you need to keep in mind that Lua is case sensitive.

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So you got to make sure that when you are typing out or referencing different variables or properties,

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that the case matches perfectly.

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Otherwise you're going to run into some problems.

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The most important thing to understand from this lecture is to be consistent with your code.

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Ensure that you are following a naming convention consistently and you don't want to do something like

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type out variable names with multiple different naming conventions.

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So as an example, if you were typing out a bunch of variable names for things in your scripts, don't

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use multiple different types of naming conventions and stuff like that, because that's extremely ugly

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and it makes your code difficult to read.

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So as you can see here, if we did something like this and we try to read all the different variable

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names, it's very inconsistent.

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None of them are using the same naming convention.

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Your eyes have to switch around between how the words are placed together.

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It's just it's awful.

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It's ugly.

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Don't ever do this.

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Another thing that I've commonly seen done when people are creating their variables is they omit or

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remove the spaces between the assignment operator and the value they are assigning to their variable.

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So I've seen people do something like this again, don't do this.

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This is very ugly.

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It's like you were writing an essay, but you decided to leave out all the spaces between the words.

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It's ugly, it's hard to read and it just looks dumb.

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So don't ever do that.

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Okay, so let's go ahead and start practicing using some variables.

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So I'm going to create a few variables here.

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And you can go ahead and follow along with me I'm going to call this variable something like quote of

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the day.

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Again we're using the camel case naming convention.

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We're going to use our assignment operator.

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And we're going to assign a string value to this.

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And the quote of the day can be something like, don't be a lazy coder.

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There we go.

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So now we have a variable.

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And this variable is storing a string data type.

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We can go ahead and create another variable.

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I'm just going to call this one a Boolean example.

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And inside of here we're just going to store a true value.

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So there we go.

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We have a variable storing a boolean data type.

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We're going to go ahead and create another variable.

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I'm going to call this one number example.

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And inside of here we can store a floating point number like 1.923.

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And then we can go ahead and create another variable.

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I'm going to call this one nil example.

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And we're just going to set this equal to nil.

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So there we go.

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Now the very cool thing is we can reference these different variables by referring to their names or

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their identifiers.

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So what we're going to do is we're going to use our print function and we're going to pass the name

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of these different variables.

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So for example here I can type out quote of the day.

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And then I can hit tab to autofill that right there.

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And then we can use the print function again.

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And we can print out our Boolean example.

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We can print out our number example and we can print out our nil example.

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Now what this is going to do is it's not going to print out the name of the variable, but instead it's

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going to look at this variable.

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It's going to find whatever is stored in memory, which in this case would be our string or this one

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would be the boolean, whatever.

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It would take that value and it's going to print it out into our output or console.

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If you do not have your output or console open, make sure you head up to the view tab and enable the

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output button, which is right here.

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So now we can go ahead and see these values get printed out in our console by going to our test tab,

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hitting this little drop down arrow here and pressing run.

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And now, as you can see, we get the different values printed inside of our console.

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So we get our message.

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Don't be a lazy coder.

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We get true printed out, we get our number printed out, and then we get nil printed out so we can

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go ahead and end the test.

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And one more thing I would like to show you is that we can also update the values inside of our variables.

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So when we instantiate or create this variable, it's not going to be stuck with a string forever.

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We can easily change the value stored inside of this variable to whatever we'd like.

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So for example, I can refer to quote of the day.

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And then to override the value inside of here, I'm just going to use the assignment operator once more.

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And inside of here I can change it to be something like a number.

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So we can put in something like 100.

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And now when our game is going to execute, it should print out 100 here and not our string because

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we first create the string and then later it gets overridden with the value of 100.

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So if we go back to the test tab and hit run.

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As you can see, our message is gone and now we have 100 printed into the console.

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This perfectly demonstrates how Lua is a serially executed programming language.

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What does that mean?

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Well, it means that Lua code is executed line by line, starting at the top and going down each line

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until it reaches the bottom of your script.

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So when our game is run, the interpreter goes into our script and it starts executing code.

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It goes to the first line of code, which would be here.

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It would be like, okay, I need to create a variable with this value inside of it.

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So it stores that information in memory.

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It goes to the next line oh, I got to do the same thing.

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Creates another variable, stores that value in memory and it keeps going down.

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And then eventually it's going to hit this line right here.

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And it's going to see, oh we're referring to a variable that we've already created previously.

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And we want to override the value stored inside of that variable with this new value.

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So it does that.

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It removes our string and replaces it with this number.

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And then finally when we get down to the different print functions it prints out those values inside

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of our console.

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In this case that would be 100 true 1.923 and then nil.

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So congratulations, you've reached the end of the first Lua basics lecture.

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This was a lot of information to digest, but you're going to be using variables all of the time, so

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it's very important you understand and get comfortable using them.

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See you in the next lecture.