Fitting a FORTH in 512 bytes

https://niedzejkob.p4.team/bootstrap/miniforth/

by jpegqs • 5 years ago

190 57 5 years ago

niedzejkob.p4.team

stcredzero2• 5 years ago

"To compile a kernel, you need a running kernel."

Why? I guess it depends on how you define "kernel." But to be able to do a batch process like compilation, you can get away with a little.

spicybright• 5 years ago

I'm guessing by kernel he meant any program that can host other programs in some way.

Can you clarify what batch process means in this case?

I /think/ the authors definition of a kernel is a program that can host other programs in some way.

A video game on a boot sector can't do that (even though it likely would have it's own kernel to function), but some kind of input loop to write memory could.

stcredzero2• 5 years ago

The old Apple II+ I had as a kid only did one process at a time. For an OS, it basically had what amounted to a REPL for Microsoft BASIC.

You don't need to host another program to compile something. All you need to do is to read data off disk, then write other data back.

NieDzejkob3• 5 years ago

Workarounds exist, like for every other example I mentioned. I am mostly referring to the commonly used dependency graph.

musicale2• 5 years ago

As the article demonstrates, all you really need is a boot loader.

On early machines (large and small) with front panel hardware, you could use switches to manually enter the boot loader into memory and then start it.

stan_rogers• 5 years ago

...and the EDSAC crew decided that that sort of thing was a mug's game as far back as 1949, so they added what amounts to a machine to do that for you (the Initial Orders unit). (No, I don't really miss the Altair, no matter how ecstatic I was about it in high school. Toogle-booting is fun maybe twice.)

astrobe_2• 5 years ago

That's precisely the joke. "Kernel" here means the minimal feature set that let you compile a kernel. The sentence is tautological, except perhaps for the definition of "minimal", because there are various flavors of "minimal" (e.g. absolute minimum, practical minimum, ergonomic minimum...).

hyperhopper• 5 years ago

I find it amusing how often trying to do complex tasks with simple constraints, always ends up back at stack based languages. Probably why the stack based turing machine is academically important.

q-big• 5 years ago

Probably why the stack based turing machine is academically important.

A Turing machine is not stack-based, but tape-based. A pushdown automaton (PDA) is stack-based.

imode• 5 years ago

Two stacks make an automaton Turing Complete. Which is an interesting result.

bear86422• 5 years ago

Although turing machine tape emulatable via 2 stacks

NieDzejkob3• 5 years ago

I suppose that prior art influences things. In my case, I went "a separate text editor won't fit, I need a REPL", and that basically filtered to just Forth and Lisp. It would be interesting to see what subset of Lisp would fit in a bootsector, but I wouldn't get my hopes up.

na852• 5 years ago

There's sectorlisp that appears to fit into two sectors but is yet shy of their single-sector goal: https://github.com/jart/sectorlisp

cblum• 5 years ago

Gonna plug my own sectorforth here: https://github.com/cesarblum/sectorforth

The linked post is really impressive. The author went way beyond what I did. I'm especially impressed by the I/O stuff.

na852• 5 years ago

Man, Forth is such a cool language. It really captures (what I perceive to be) the "hacker mentality" of powerful but simple tools, without much overt concern for polish/slick interfaces.

I mean I know a lot of foundational code of yesteryear was hacked together in C, but C lacks a certain ineffable cachet in my view. A cachet that Forth definitely has.

kabdib2• 5 years ago

FORTH is a fun little class of languages. These are easy to implement; in a few KB you can have a working development environment, with a screen editor, debugger and whatnot.

In my experience, FORTH doesn't really scale to big projects, or things that need a lot of dynamic allocation. It's great at low-level stuff like hardware bringup (we used it on the Atari ST, back in the day, and even the hardware engineers were writing code to exercise their designs), but doing anything at scale is going to be tough. You probably don't want to write a modern web server platform in it, for instance. But it's probably great on an Arduino with a serial port.

There were a lot of games started at Atari in FORTH ("Hey, this is simple! Who needs to hire expensive assembly language programmers?") but the only project that shipped was the pinball machine "Four by Four". I saw a bunch of expensive disasters and mostly steered away from it.

NieDzejkob3• 5 years ago

This reminds me of this video on a text processing example with Forth: https://www.youtube.com/watch?v=mvrE2ZGe-rs

bluedino• 5 years ago

Weren’t some 7800 games written in Forth?

dingosity2• 5 years ago

Worms? was a FORTH jam, or at least that's what David Maynard said in a recent interview (since it seems this thread is becoming a list of FORTH games.)

perl4ever2• 5 years ago

I associate Forth with astronomy.

o8r3oFTZPE• 5 years ago

Two ways to "scale". Up or down. FORTH scales down.

Interesting how developers today impicitly assume the term "scale" mean "scale up".

thesz• 5 years ago

If you need dynamic allocation, you can invent a Forth dialect for your specific needs. And implement it in Forth. A domain-specific language for your problem domain, embedded in Forth.

Consider control statements like conditionals or loops. They are implemented in Forth to express what is essential for imperative programming.

You can just as easily implement region handling much like what Cyclone [1] did. Invent region, dispose region, allocate within region, etc. You can augment semicolon word to not only check for control statements to be valid, but also check for region handling correctness.

[1] https://en.wikipedia.org/wiki/Cyclone_(programming_language)

Of course, you have to be either well educated or highly inventive to do that. ;)

And at the time of Atari most of programming projects were expensive disasters, not only games written in Forth.

guenthert• 5 years ago

Forth on Atari w/o mentioning https://atari8bit.net/db/?d=cd&g=Books&f=FORTH-on-the-Atari-... Yep, those were the times.

FORTH is all fun and such (well, the stack counting gets old after a while), but I have difficulties seeing it in larger, multi-person projects (were there any?). A good idea who's time came and went.

chalcolithic• 5 years ago

I hope I'm not breaking any rules by saying that I enjoyed your blog immensely over the years

dingosity2• 5 years ago

people talking about how cool FORTH is. @cblum made his own sector forth. this is my tribe. i honestly thought there were no stack fans left in the world, thanks for proving me wrong.

garmaine• 5 years ago

Check out Bitcoin’s script language sometime.

tromp• 5 years ago

Postscript, the printer page description language, is a general purpose programming language in common use, also as the basis of PDF.

int_19h2• 5 years ago

One has to implement FORTH oneself to truly grok it.

musicale2• 5 years ago

OpenBoot/Open Firmware[1] also used Forth.

Although the standard was withdrawn in 2000, it continued to be used by PowerPC Macs until Apple moved to x86 and EFI/UEFI.

Open Firmware is now actually open source as OpenBIOS (and OpenBoot is also available under a BSD license.) Apparently it can be used as a qemu boot rom for Linux, BSD, Solaris, and PowerPC versions of Mac OS 9 and OS X.[2]

[1] https://en.wikipedia.org/wiki/Open_Firmware

[2] https://www.openfirmware.info/OpenBIOS

timonoko• 5 years ago

There must be lots of ole-school fixed-width machines, which have stack machine built-in. Especially if you decide that top-of-stack means contents of the accumulator(s). To make it a "forth", you need separate string space, where machine words are linked to symbols. 1+ for example is just INC.

int_19h2• 5 years ago

Many modern RISC architectures have pre-increment and post-decrement addressing modes for all their general-purpose registers, so it's very easy and convenient to maintain multiple stacks and implement "NEXT".

throwaway81523• 5 years ago

Seems painful. I liked this approach better:

https://github.com/nineties/planckforth

You start with a very tiny address or bytecode interpreter, much smaller than 512 bytes. Then you load several levels of bootstrap interpreters into it until you have a fairly featureful Forth. So that occupies ram but not program space on the target computer. You would load the non-initial stuff from a remote computer that didn't have tiny memory constraints.

1vuio0pswjnm7• 5 years ago

Will this run in Bochs.

Fitting a FORTH in 512 bytes

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