Startup banner

The previous blog post marked the end of epic 3 development, so the “team” had another retro and we all agreed that everything had gone swimmingly. Next up is a built-in assembler! This was a crucial feature of early Forths and was
one of the main reasons Forth was often the first thing ported to a new board or device: it gives you a real-time execution environment where you can test out hardware andbegin software development with very little to port. Forth’s ability to metacompile (define new words for a target system on a more highly specced host system) was another huge draw.

As I’ve previously mentioned, Forth’s built-in assembler was the inspiration behind BBC BASIC’s built-in assembler: a huge advantage over the ZX Spectrum at the time, and the reason that a lot of folk started their assembler journey with 6502 rather than z80 (until they could get their hands on a hooky copy of the incomparable ZEUS z80 assembler, that is!)

But first a digression: AntForth is currently 6953 bytes and contains 124 words and is approaching “genuinely useful” status: and as such, I think it deserves a startup banner! So I created a new story (4.0) to implement one.

antforth.asm

The new startup banner is implemented in proto-Forth, and I’m not including the source code here so as not to ruin the big reveal! You can look in the github repo for details, but it’s nothing too earth shattering. Look for cold_thread and you’ll find it.

Here’s the new startup banner:

Pretty sweet right? Most of the complexity in the startup banner is to do with working out that free bytes total, and I swiped the “type BYE to exit” from GForth, as that’s pretty handy advice for beginners (AntForth has no truck with ctrl-c getting you out of trouble).

But wait! There’s more! Let’s zoom out slightly from that previous screenshot…

It was running on the MicroBeast the whole time!!

We’ve got just under 48K of free space, not bad at all. Compare this with AntForth running under iz-cpm:

I guess iz-cpm has a slightly smaller BIOS.