programming-for-dummies

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Scripting Languages
Rather than write an entirely new program from scratch using a systems programming
language, more people are likely to use an existing program and
customize it in some way. Programming languages that customize existing
programs are typically called scripting languages.
Scripting languages work with one or more existing programs and act as
“glue” that connects different parts of an existing program together. For
example, the Microsoft Office suite consists of a word processor (Microsoft
Word), a spreadsheet (Microsoft Excel), and a database (Microsoft Access).
By using the scripting language that comes with Microsoft Office, you can
write a program that can automatically yank information from an Access
database, create a chart from that information in an Excel spreadsheet, and
then copy both the data and its accompanying chart into a Word document
for printing.
Trying to yank information from a database, create a chart with it, and print
the data and chart using a systems programming language, like C++ or
Pascal, would mean creating everything from scratch including a database, a
spreadsheet, and a word processor. By using a scripting language, you use
existing components and simply “glue” them together. The existing components
do all the work while the scripting language just passes the data from
one component to another.
Because scripting languages work with existing programs, they differ from traditional
programming languages (like C++ or BASIC) in two important ways.
First, because scripting languages work with one or more existing programs,
scripting languages are usually interpreted rather than compiled. Therefore,
if someone else wants to run your program, written in a scripting language,
they need the source code to your program along with all the programs your
scripting program needs, such as Microsoft Word and Microsoft Access. As a
result, scripting languages are used less to create commercial applications
and more to create custom solutions.
Second, to make scripting languages easy to understand and use, even for
non-programmers, most scripting languages are typeless languages. (Systems
programming languages, like C++ and Pascal, are strongly-typed or type-safe
languages.)
Strongly-typed languages force you to define the type of data your program
can use at any given time. So if your program asks the user to type a name, a
strongly-typed language makes sure that the user doesn’t type in a number
by mistake. This protects a program from accidentally trying to manipulate
the wrong type of data, which could crash the program as a result.