AppleScript: The Definitive Guide, 2nd Edition

Compiled Script Files

A compiled script file is just what you think it is: it's a file containing the bytecode of a compiled script. Unlike text, a compiled script file can be executed without being compiled (because it's already compiled); the runtime engine is fed the bytecode and can leap into action immediately. A lengthy script can take several seconds to compile, so a compiled script file clearly saves some time and overhead when the script is executed. Obviously this architecture is advantageous when the script is not going to change and therefore will not need compiling ever again—when you distribute the script to others, for example. Applications that act as script runners typically operate on compiled script files (see "Script Runner" in Chapter 2). Script editor applications save a script as a compiled script file by default. When an application has asked the AppleScript scripting component to compile some text, a compiled script file is the only way for the compiled script to outlive that instance of the AppleScript scripting component, which will go out of existence when the host application quits.

(There is actually more to a script, and therefore there can be more to a compiled script file, than the compiled bytecode. I'll discuss these further contents of a compiled script file in "Persistence of Top-Level Entities" in Chapter 8 and "Closures and Stored Script Objects" in Chapter 10.)

You cannot save as a compiled script file code that, for whatever reason, will not ...