What is a Variable?

A variable is a label that refers to a value stored in memory. Let’s explore what that means:

x = 5

The name of the variable (x in this example) is on the left side of =, and its value (5 in this case) is on the right. = is the assignment operator. Here it assigns the variable x to the value 5. When you first assign a variable to a value, you also define that variable. A defined variable has meaning in the program, e.g., x means 5.

By assigning a variable to 5, we indicate to the Ruby interpreter that the integer 5 is worth storing in memory. The variable "stands in" for the value, giving the programmer a convenient way to retrieve and manipulate data in more complex problems. For the example below, remember we assigned the variable x with a value of 5.

x + 2
=> 7
puts x
5
=> nil

Any object can be assigned to a variable (e.g., b = "dog"). Variables can also be reassigned (a = b). Run each of the following lines from the file (by clicking run_), and check out the result in the Repl.it shell.

Predict the new values of a and b. Type a in the shell and press enter. Do the same for b.

a
=> 7.5
b
=> true

When b is reassigned to a, a refers to true. The value of b therefore also becomes true. The later reassignment of a to 7.5 does not affect the value of b.