AppleScript: The Definitive Guide, 2nd Edition

Kinds of Variable

With regard to scope, we must distinguish four kinds of variable:

Top-level entities

Top-level entities are script properties declared, and script objects and handlers defined, at the top level of a script or script object. (See "Top-Level Entities" in Chapter 8.)

Explicit locals

An explicit local is a variable announced by a local declaration , which looks like this:

local x

Explicit globals

An explicit global is a variable announced by a global declaration, which looks like this:

global x

Undeclared variables

A undeclared variable is none of the above. It's just a name that your code suddenly starts using. This is legal, but when you do it, AppleScript assigns the variable a scope , in ways that may surprise you.

The scope of a variable, and what kind of variable it is (these amount to the same thing), are determined at compile time .