What's the difference between a programming language, a scripting language, and a markup language?

While the previous descriptions of the three "languages" explain them, and distinguish between the two "procedural" languages that describe procedures to run, and the "formatting" languages that "mark up" data, a simple nuance can be used to distinguish between "programming" and "scripting" languages, especially those in the fringe areas.

Using the question of compilation versus interpretation to define languages gives a "fuzzy" definition for languages like Java, which can be compiled to a byte code which is then interpreted at runtime. And there have long been programming tools such as Borland's Turbo C / Pascal which would interpret languages that were normally compiled, to allow more rapid development.

The difference between "programming" and "scripting" is better defined by usage, or application, as well as scope and purpose. A programming language is used for building standalone projects, or "applications"; a scripting language is used to write "scripts" that interact with other data or systems to perform parts of a task rather than an entire workflow.

An example might make this clearer. Imagine an accounting application program used in a large corporation. The program would be written in a programming language by a team of developers, probably at some other company, a software house. It would have a long lifecycle, and have many features. One of them might be to generate a series of invoices. This would be one of many tasks done with the program, which runs for extended periods of time. But it might be necessary to separate the invoices, sending some to a printer in the mail room, others to a fax machine, and still others to be sent via email. This task might be accomplished by a local programmer, who writes a simple "script" that sorts through the accounting program's output files and dispatches them appropriately. That little snippet of local, customized programming would be a script, written in a scripting language. The script would be started, perform its one task, and stop.

Programming languages are used to write programs, which can run for a while and do multiple things.
Scripting languages are used to write scripts, which run for a short duration to perform a single, simple task.

Of course, there are applications programs that have been cobbled together out of collections of scripts, and there are programmers who use a traditional programming language to write a full-blown program to erase a file, but the general sense of the range of usages should now be clear.

Some languagees such as Perl or Visual Basic can be used for both kinds of task, and therefor can be characterized as one or the other.