HN Reader

Hi, author of Jacqueline here. I read HN almost daily so it caught me off guard to see my stuff here.

It's been a long time since I did this (2019). It was a prototype just to see if a standard PC boot loader could hand-off into something that's not C (or Rust). And yes you can, as long as the programming language has a way to control how symbol names are exported, and then to link the object code with the rest of the boot loader.

You won't have a runtime unless you implement one, so for most languages there is no stdlib, no exception handling, no garbage collector... But it is fun anyway. As I said, this was a prototype and once it could say Hello World I considered it complete.

Happy to see it here though, and I'll be happy to answer any questions about what I remember, or what is like to write code in Pascal, or OS development or i386 in general.

I remember writing my own bootloader for my DOS-successor OS project with its own FS when I was 17. Never got around other than running a primitive kernel that just displayed text on the screen though. Fun times! https://gist.github.com/ssg/546634

Thats the pascal kernel in all its glory. Its just a bare metal hello world

KernelMain(); [public name 'kernelMain']; begin consoleClearDisplay(); consoleSetAttributes(White, Black); consolePutString('Hello world'); end;

> Even while Pascal wasn't written with low-level programming in mind

If that’s true, then neither was C, Algol, etc. When those languages were conceived, “low-level” programming was just “programming” and “high-level programming” was the exception. Mostly because the hardware ecosystem was far more fragmented and an OS wasn’t guaranteed.

To that effect, all of those languages give you the “features” necessary to “low-level” program, namely: raw pointers and ability to compile for freestanding environments.

Love it

> Jacqueline is an experimental bootloader written in Pascal (Free Pascal dialect) written for the i386 architecture, just because

i386 is a great target for toy OSs. There's no risk of getting a bit megalomaniacal and thinking your OS could ever be anything more than a toy. Also, it's more challenging than RISC-V, ARM, and even x86-64, so it feels like more of an accomplishment if you actually make it to userland and back without catastrophic failures.

Remember kids, there were a few 1980's OSes that made use of Pascal.

Nice to see yet another experiment that isn't always C or C++.

Finally an OS I can really get behind.

Pascal? The author must hate himself.