# Using of variables

In order to use a variable, you should first declare it: put the keyword `let` before its name. Let's declare, for example, the variable named `a`:

`let a;`

After the variable declaration, you can write to it (they say to assign to it) some value, such as some number or string.

Writing data to a variable is done using the assignment operation `=`. Let's, for example, write the number `3` into the variable `a`:

`let a = 3;`

And now let's display the contents of this variable on the screen using the `alert` function:

`let a = 3; // declaring a variable and assigning a value to it alert(a); // shows 3`

It is not necessary to write the value into the variable immediately after the declaration. You can first declare a variable and then assign a value to it:

`let a; // declaring a variable a = 3; // assigning value to it alert(a); // displays the value of the variable on the screen`

As you see, `let` is written only once before a variable name - when you declare this variable. To use a variable further, you need only write the name of this variable.

Create the variable `num` and assign the value `123` to it. Display the value of this variable to the screen using the `alert` function.

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