Hi. In this second section about algorithmics, we will talk about variables. The first question is: What is a variable? A variable is a memory space, whether local or remote, where the program stores a value or something more complex, like a data structure which is more complex than a value. Clearly, the variable's value is expected to change during the execution of the program, although constant variables are also a possibility. Some examples: the number of followers: the number of people who follow you, the number of views of a video on YouTube, the number of likes. Those are all integer values. Another example is a student's average, but it would be instead a real number. In fact, in a computer, it is stored as a floating-point number. You can also have all the class's grades. It can be an array, an array of arrays, a database or more complex representations. For all this, I would advise you to watch Brice's sequence about data organisation. And there is a certain number of more complex data structures. I won't go into details, I'll just give you the names so that you can do some research, those are hash tables and doubly-linked lists. Normally, a variable needs to be created. That depends on the programming language. Some of them actually create one automatically as soon as a variable is used. It can be assigned, so a value can be input, like 0, 45, etc. It may be modified from preexisting variables. A regular assignment is I get i+1, which means considering the value of i, adding 1 to it and rewriting on i's memory space this new value. So if I equal 3, after that instruction I will be equal 4. A variable can also be the program's entry, which means a function can have a certain number of arguments which then become variables also. There is a certain number of variable types, which means that when you declare a variable, it is given a type : what kind is it? Is it an integer? Is it a chart? It can be an integer, it can be a floating-point number, so a real value. It can be a chart, in that case, it must be specified what is in the chart. It can be an integer chart or a floating-point number chart. In certain programming languages, the chain of characters can be considered as characters charts, but that's not always the case. It can be pointers, which means an arrow creating a link towards a memory space. Or it can be composed of structures. For example, two reals forming an interval or a chart and the length of this chart. We can have a composed structure made of a simpler type regroupment.