[vertnerd]

I was captivated by the August 1980 issue of Byte magazine, which had a cover dedicated to Forth. It was supposed to be easy to implement, and I imagined I might do that with my new KIM-1 6502 board. Alas, the KIM-1 was lost when I went to college, and life forced me down different pathways for the next 45 years.

About a year ago I finally began to work on my dream of a Forth implementation by building a Forth-based flight management computer into a spaceflight simulation game that I am working on. Now, instead of writing mostly C# or GDscript code in Godot, I am trying to figure out ways to create a useful device using this awkwardly elegant language. I'm having fun with it.

One of the interesting bits is that I have been able to make the Forth code an entirely separate project on Github (https://github.com/Eccentric-Anomalies/Sky-Dart-FMS), with a permissive open-source license. If anyone actually built a real spacecraft like the one in my game, they could use the FMS code in a real computer to run it.

There is one part of the linked article that really speaks to me: "Implement a Forth to understand how it works" and "But be aware of what this will not teach you". Figuring out the implementation just from reading books was a fascinating puzzle. Once I got it running, I realized I had zero experience actually writing Forth code. I am enjoying it, but it is a lot like writing in some weird, abstract assembly language.

[PaulHoule]

Circa 1980 BASIC was the dominant language for micros because you could fit BASIC in a machine with 4k of RAM. Although you got 64k to play with pretty quickly (1983 or so) it still was a pain in the ass to implement compilers on many chips, especially the 6502, which had so few registers and addressing modes that you're likely to use virtual machine techniques, like Wozniak's SWEET 16 or the atrocious p-code machine that turned a generation of programmers away from PASCAL.

FORTH was an alternative language for small systems. From the viewpoint of a BASIC programmer in 1981 the obvious difference between BASIC and all the other languages which that you could write your own functions to add "words" to the language. FORTH, like Lisp, lets you not only write functions but create new control structures based on "words" having both a compile-time and run-time meaning.

FORTH's answer to line numbers in BASIC was that it provided direct access to blocks (usually 1024 bytes) on the disk with a screen editor (just about a screenful on a 40x25) You could type your code into blocks and later load them into the interpreter. Circa 1986 I wrote a FORTH for the TRS-80 Color Computer running the OS-9 operating system and instead of using blocks it had POSIX-style I/O functions.

FORTH was faster than BASIC and better for systems work, but BASIC was dominant. Probably the best way to use FORTH was to take advantage of it's flexibility to create a DSL that you write your applications in.

[area51org]

I had that issue, and I think I still might have it in my closet. (Weren't those Robert Tinney covers amazing?)

I always wanted to try out Forth but had no real opportunity. Maybe I should now?

[mvidal01]

https://archive.org/details/byte-magazine-1980-08