Welcome to Forth

Welcome to Forth, a mid-level, interactive, word-based language (see below for a note about what "word-based" means.) In the language abstraction spectrum, Forth lies somewhere between assembler and system languages like C. Forth can be used as a "portable assembler", but it also supports the simple construction of arbitrary higher-level abstractions such as object-orientation. Forth's middle-of-the-road abstraction level and interactive nature addresses the following specific perceived shortcomings of other mainstream languages. Note that while there are many languages with one or more of Forth's features, Forth is unique in that it combines them all in one tool:

• Unlike many popular system languages, Forth is fully-interactive; no edit/compile/test cycle is required. Instead, you can edit and run code directly from the Forth command line. This means that exploratory programming is very easy in Forth. (However, the fact that control structures usually can't be used outside procedure definitions somewhat limits one's ability to run ad-hoc code at the command prompt.)
• Unlike many popular scripting languages, Forth can compile directly to native code, which means you can have native-code performance in a fully-interactive environment.
• Unlike many popular languages, Forth does not impose any particular structure to your code (no "everything is an X"); you are free to use procedural, structured, object-oriented, and limited functional techniques as circumstances warrant. (However, you may need to build your own toolbox.)
• Unlike virtually all popular languages, a complete Forth development environment can run in a surprisingly small memory footprint (a few 10's of K for a really large, highly-functional implementation), and without an underlying general-purpose operating system. Furthermore, the Forth compiler typically produces very compact object code. This makes Forth ideal for exploratory programming in embedded and resource-constrained environments.
• Unlike most popular languages, Forth makes it possible and natural to directly manipulate the hardware on which the Forth system runs. Such direct manipulation can be done from the Forth command line -- another advantage when doing exploratory development in embedded environments.
• Unlike most popular languages, Forth is extensible - it allows the programmer to add to the language facilities (such as control structures) that are completely indistinguishable from the built-in facilities. Forth takes you beyond the ability to design libraries, and makes you a partner in the design of the language itself; building a high-level language atop the Forth environment is therefore fairly simple. Further, any such high-level language can be made immediately available to the user as well as the programmer. (Note: do not use this power in the service of evil!)
• Unlike nearly all popular languages, the internal structure of a Forth development environment is extremely simple and easy to understand, even for folks with little programming experience. While to an experienced C programmer, for example, Forth may seem to be full of strange inconsistencies and edge cases, a full understanding of the nature of Forth makes it clear that all of its features are natural consequences of its simple and elegant implementation; and such a full understanding is easy to achieve.
• Because Forth permits the programmer both to manipulate the low-level hardware interafaces of the system, and to build arbitrary abstractions, it makes a very good language with which to learn programming.
• The flip side of that is that in order to use Forth most effectively -- and sometimes merely to use it correctly -- the programmer must throughly understand both the low-level details and the high-level abstractions. That can be a good thing: a wise man once said that a programmer working at a particular level of abstraction should thoroughly understand both the level below (so as to make proper use of the underlying facilities) and the level above (so as to build genuinely useful tools). Forth strongly encourages this.

Notes

Some time ago I was involved in a discussion of Forth evangelism on comp.lang.forth. My position was that a lot of Forth propaganda seems to be of the "Drink the Kool-Aid" variety -- cult members preaching to the converted. In an attempt to develop a fair and unbiased description (to the extent such a thing is possible), I came up with the text above. It is my personal view of the Forth language and philosophy; if you don't like it, that's your prerogative. If you do like it, excellent :-)

What does "word-based" mean?