Kenneth Cochran

Haven't seen this asked yet but does Mad Pascal support targeting the Atari 2600?

This is an awesome idea. My goals are slightly different. I'm focusing primarily on making it easier to implement high level languages. Forth is one of the easier languages to implement due to it's minimalist design philosophy and extensibility but I'd like to see more popular languages and I'd like to target other game systems as well. After doing some research I've concluded that the CLR and JVM are too modern to target these early game systems. They were designed around the larger address space of 32-bit and 64-bit processors. Even the VMs that target embedded and resource constrained environments still expect far more resources than a 4th gen game system let alone a 1st gen one. So I'm leaning toward a lightweight interpreter that implements a stack machine. I may start with a Forth or p-machine interpreter and adapt it from there. One thing I'd like to do is give the game developer fine grained control over which code is interpreted and which is compiled to machine code that way they can fine tune performance. Another idea I had was to create an assembly language for the virtual machine that could be directly implemented by languages that support inline assembly. But this is just the tip of the iceberg. I'd eventually like to use this as a springboard to create a small, single process operating system that provides abstractions for common game system features as libraries.

I've been thinking about how to make programming for the 2600 even more accessible and the idea struck me that many high level languages for early microprocessors like the 6502 used threaded code interpreters to squeeze larger programs into those memory constrained systems. Examples include Forth, several variants of Pascal P-systems and some BASIC variants as well. The P-systems even had other languages target the P-code in much the same way languages target the JVM or the CLR today. This came at a cost of course. These techniques were essentially early forms of virtual machines that traded performance for instruction density. But all examples I've read about seemed to have higher memory requirements than the 2600's meager 128 bytes of RAM. Forth programmers used to boast that a minimal Forth system could be implemented in under 2Kb of RAM. It occurred to me that if a bare bones threaded code interpreter is feasible it may have too much memory overhead to justify it's use. And even if the memory overhead is small it may be too slow to be useful for game development. Still, the idea is intriguing. Anyone have experience with these systems? How useful were they? My first computer was a Tandy 1000 HX with the memory expansion and I didn't start programing until the Pentium era so I have no point of reference.