--- title: Intro to values and types in ruby slug: intro-to-values-and-types-in-ruby published_at: 2020-09-07 01:14:59 +0000 updated_at: 2026-03-04 20:14:48 +0000 summary: description: tags: [] views: 1947 author: CJ Avilla url: https://www.cjav.dev/videos/intro-to-values-and-types-in-ruby youtube_url: https://www.youtube.com/watch?v=_h45Ty1mPJ4 youtube_id: _h45Ty1mPJ4 embed_url: https://www.youtube.com/embed/_h45Ty1mPJ4 thumbnail_url: https://i.ytimg.com/vi/_h45Ty1mPJ4/hqdefault.jpg type: video --- # Intro to values and types in ruby *Published: September 07, 2020* *Views: 1947* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=_h45Ty1mPJ4) [![Intro to values and types in ruby](https://i.ytimg.com/vi/_h45Ty1mPJ4/hqdefault.jpg)](https://www.youtube.com/watch?v=_h45Ty1mPJ4) ## Description ## Transcript a computer program is a list of instructions that can be followed by a computer to perform a specific task most programs work by taking some input data processing that and creating some output data understanding the values and types will form a foundation on top of which we can build up concepts that will allow us to write our own programs so values are the actual underlying raw numbers and text our program manipulates tony stark the number 43 and false are all examples of values sometimes we'll say that when we literally write the number four and then the number three next to each other to form the number 43 that we're writing the literal 43 same with tony stark if we write the quotes then the letters t o n y etc into our code we'd say that we're using the string literal tony stark sometimes we might say that this is hard coded meaning that when the program runs the literal value isn't going to change literal values are used a lot when you're first starting out but eventually data will likely come from a database or some user input every value belongs to exactly one data type the kinds of values that can be represented and manipulated in a programming language are known as types all of these literals that we've written so far can be categorized as a specific type we see string number and boolean those are the types for tony stark 43 and false most languages use a very similar list of super simple types like a collection of characters as a string of text a list of digits with or without a decimal point as a number and then some type for representing true and false some programming languages will have more types that they have built in other programming languages will have a very small set of these primitive built-in types that you are to use to build up to more complex types when a program needs to use a value again in the future it assigns that value or sort of like stores that value in a variable variables have names and they allow us to use those names in our programs to refer back to the values we'll talk more about variables later here we're assigning the value 7 a name age we're also assigning the string grayson to the variable name first name if we wanted to print out the value 7 using the variable age we might call some print function and pass in the variable name or the literal number 7 and we'll take a look at how to print out the number or the string or whatever value it is in different programming languages there's really two different kinds of types there are built-in types and then there are user defined types built-in types are the types that come with the language this is the batteries included stuff like numbers and strings and dates and arrays and object types user defined data types are defined in terms of built-in data types and other user-defined data types here we're defining a student type or we have defined a user-defined type called a student type which is composed of or made up of other built-in types the number for the the age and the string for the first name we might also create a car type which takes in a make and a model both of which might also be user defined types typically a programming language does not let the programmer extend or redefine those built-in types next a type can either be mutable or immutable these primitive types like 7 and true are immutable meaning they cannot change you can change the value of the variable meaning you can change what the name of that variable is referencing by pointing the variable at a different value however there's no way to change what the number seven means when we talk about the number seven there's no way we can like modify the number seven to be the number eight or the number six we wouldn't want to change what the number seven means similarly with true we wouldn't want to change what it means for something to be true a mutable object can change here we have an array or a list and this list has four values it has 9 10 9 and 11. these might be ages or these might be other values but the the underlying type for this collection of values is called a list a list or an array in some languages can change all right let's learn how to work with values in ruby today i'm working with reppl.it it is a tool that lets you execute ruby programs on the right side we have a pane which represents our terminal output in the middle we have a pane that represents our editor main.rb is the file that we're going to be editing and when we click run it will execute our ruby code and show the output on the right hand side if we click run right now we have no code written so there is no output it shows us that it ran the command ruby and the input file name was main.rb the very first thing i want to do is print something to the console so i want to i'm going to use the puts method or the put s method here and pass it a number literal so we're just going to pass it the number 1 and click run and this will evaluate the expression one find out what the string value should be for that and print it out to the terminal so we see one show up in our terminal here the next thing i want to show you is how you can add comments so by adding the octothorpe we are commenting out this bit of code so we can add this um the pound sign or the hashtag sign the octothorpe whatever you want to call it at the beginning of the line to start the beginning of a single line comment so we are commenting out this code comments are generally used to describe what's happening in your code and make it easier for a human to read through your code and for you to remember what certain what certain code is doing so here we're commenting outputs1 so that i can keep track of and share with you the different commands that we have run so far so i'm commenting outputs1 i'm going to make a new line by hitting enter and on this next line i'll show you just another simple example we're going to say put s the number 43 from our earlier example and you'll see that 43 prints out to our terminal so that's great the next thing i want to do is print out the name tony stark so we'll say put s tony stark and then execute and you'll see what happens here is we get an error and it says uninitialized constant stark and that is a name error so it's it's uh one really important thing about programming in general is being able to read an error message and try to understand what the computer is telling you about what it tried to do and what it was unable to do and like how it failed so in this context we're calling the puts method this built-in method and we're passing in a value and the value that we want to give it is a string of characters for the name tony stark but when the ruby interpreter is running this program it doesn't actually know where the string is starting and where it's ending so here we need to use some quotes to wrap the string and when we define the string literal and pass it into puts we want it to know where the string starts and where the string ends so in ruby we can use uh single quotes to define a string literal we can also use double quotes we can there's also a couple other really fancy ways to add to create strings in ruby but today we're going to work with just single quotes in double quotes the primary difference being with double quotes you can do this this fancy thing called string interpolation which we'll talk about much later so we have a our single quote at the beginning that tells us where the string starts in our single quote at the end telling us where the string stops and we're saying to print that string to the console so if we run this now we'll see that tony stark is indeed printed to the console so that's great all right so what what else can we do here though so one thing that we might want to do is uh show that we can if we use a a double quote in the beginning and a single quote at the end if we try to run this code it will fail again because the the ending quote the style of the ending quote needs to match the style of the beginning quote if the beginning quote is a double quote the ending quote also needs to be a double quote if the beginning quote is a single quote the ending quote also needs to be a single quote so here we have a double quote to begin and a double quote to end and we are able to print out tony stark great let's keep going so we have another thing we can show is that we can print out an expression so if we say 43 plus 10 we're going to print out the result of the expression 43 plus 10. so here what's happening is the very first thing we're going to do is evaluate the expression on the right hand side that you can sort of think of this expression being the the literal number 43 this operator the plus operator and then the value 10 these three things combined gives us an expression that expression will be what we call evaluated so the computer kind of just figures out what is 43 plus 10 and then it replaces this expression with that new value so it will replace it by with 53 before passing that value to puts which will then print it so if we say 43 plus 10 here and then click run we're going to get the numeric evaluation of 43 plus 10 which is 53 so that's kind of what happens when we're evaluating an expression before passing it into puts so we're using two number literals and the plus operator and that gives us kind of like the arithmetic output that we would expect um you know just like from from math from what we know from math um okay so this is also useful when we're working with strings so we can say puts tony plus stark and that will evaluate tony the string literal tony so we're going to use a string tony then the plus operator again and then stark so in this case there is no mathematical way to add tony in stark right but we can use in ruby the plus operator will perform this thing called concatenation and so concatenation is the linking of a series of things together so we are going to concatenate the string tony with the string stark and if we click run we'll notice that the output here is tony stark and there's no space between tony and stark there's no space between the first name and last name because in the strings that we concatenated together there were no spaces at the end of tony or at the beginning of stark so if we wanted to print out tony space stark we could either put a space at the end of this this tony string or at the beginning of stark and then when we run we get tony space stark another alternative would be to say tony plus the empty string or like a a string with um a space in it plus stark so this is going to be we're going to evaluate this expression so we'll have space stark and then we'll evaluate tony plus space stark and then we'll get back tony stark so we can use string concatenation here when we're printing out strings we could also print out boolean values in ruby so we have the boolean value true so we might just print out true and that looks like that same with false in ruby the values the boolean values for true and false are all lowercase the word true in the word false let's see we could also print out type information about the value if we then want to inspect a floating point number like 43.123 we can we can print that out and we'll get back float so this is one way that we can inspect the class type for a for a value [Music] you --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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