In the previous example, I assigned values to variables such as subtotal, tax, and taxrate. Variables such as these that begin with a lowercase character are called local variables. This means they exist only within a specific part of a program—in other words, they are restricted to a well-defined scope. Here is an example:

variables.rb

localvar = "hello"
$globalvar = "goodbye"

def amethod
    localvar = 10
    puts( localvar )
    puts( $globalvar )
end

def anotherMethod
    localvar = 500
    $globalvar = "bonjour"
    puts( localvar )
    puts( $globalvar )
end

In the previous code, there are two functions (or methods), amethod and anotherMethod, each of which is declared using the keyword def and contains code up to the keyword end. There are three local variables called localvar. One is assigned the value "hello" within the “main scope” of the program; two others are assigned integers within the scope of two separate methods. Since each local variable has a different scope, the assignments have no effect on the other local variables with the same name in different scopes. You can verify this by calling the methods in turn. The following examples show output in comments followed by the => characters. In this book, output or returned values will often be indicated in this way:

amethod           #=> localvar = 10
anotherMethod     #=> localvar = 500
amethod           #=> localvar = 10
puts( localvar )  #=> localvar = "hello"

On the other hand, a global variable—one that begins with the dollar sign character ($)—has global scope. When an assignment is made to a global variable inside a method, that affects the value of that variable elsewhere in the program too:

amethod            #=>  $globalvar = "goodbye"
anotherMethod      #=>  $globalvar = "bonjour"
amethod            #=>  $globalvar = "bonjour"
puts( $globalvar ) #=>  $globalvar = "bonjour"