programming-for-dummies

Scripting Languages 77
Transferring data among multiple programs
Built-in scripting languages can help you automate or customize a program,
but what if you use a program that doesn’t include a scripting language? Or
what if you need to transfer data between two or more programs, but neither
program uses the same scripting language? In these cases, you’ll need to use
a scripting language that isn’t tied to any particular program, such as Perl,
Python, Ruby, or JavaScript.
When scripting languages link two or more programs together, the scripting
language programs are often referred to as glue. So if you have a Web page
that lets users type in their names, addresses, and credit card numbers, and
a database program that stores customer information, you could use a
scripting program to glue the Web page to the database. The user would
type information into the Web page, and the scripting language would then
yank this data off the Web page and shove it into the database.
Book I
Chapter 3
Types of
Programming
Languages
By gluing programs together, scripting languages let you combine existing programs
to create custom applications. Because scripting languages are interpreted
rather than compiled, they can run on any computer with the proper
language interpreter. So whether you use Windows, Linux, or Mac OS X, you can
still use the same scripting language (and programs) on different computers.
Creating separate applications
Because scripting languages are so easy to understand and use, some scripting
languages can create standalone programs. One of the most popular
scripting languages used for developing standalone programs is Visual Basic.
Unlike scripting languages, like Perl or Python, which link separate programs
together, Visual Basic links program components together. To create a Visual
Basic program, you design the program’s user interface consisting of pulldown
menus, buttons, and check boxes. Then you write Visual Basic commands
to link all these separate user interface components together to
create a working program.
Like most scripting languages, Visual Basic isn’t compiled to machine code like
traditional programming languages, such as C++. Instead, Visual Basic programs
get stored in an intermediate (p-code) file. To run a Visual Basic program,
include a special run-time file, which interprets the p-code file and actually
runs the program.
Another popular scripting language used to create standalone applications is
Revolution, which uses a scripting language similar to AppleScript. Like Visual
Basic, Revolution doesn’t compile your programs into machine code. Instead,
Revolution creates an intermediate file (p-code) that attaches directly to a
run-time interpreter. Because the Revolution run-time interpreter can run on