Forth Progress Update

My standalone Forth for the x86 is coming along nicely. I make little bits of progress every time I work on it. Right now it can compile new words, variables, and constants, as well as do simple arithmetic. The command line interface needs work, but it already displays the system state (compile = 0, interpret = 1) in the bottom right corner of the screen, and shows the top 5 items on the stack on the bottom left corner (with the top of the stack on the right).

The next things I want to tackle is to factor out the screen information, the command line information (to which I want to add a command history so I can press down and up to cycle through commands), and so attach to each key a forth word call-back. I want to talk a little bit about that in this post.

I want different keys to do different things, and I would like to be able (when the system is better developed) to attach an arbitrary forth word to a key. When I say attached I mean that the each key gives you a fixed integer value, which I use as the index into an array of characters to get the character value (the keyboard doesn't just give an ASCII value). In addition to this use of the key as an index, I want to also index the integer given into an array of execution tokens (which are basically forth's equivalent of function pointers). The interpreter would read in a single character from the keyboard and call the word (function) in the character's index. This would allow me to customize the keyboard easily, and may help when I (waaay in the future) add a text editor. Most of the time keys will be attached to a word that calls putch (put the character on the top of the stack to the screen and move the cursor one position over), but keys like enter, the arrows, backspace, and possibly other will need special handling that is done as part of the outer interpreter right now and can't be configured easily.

One interesting use of this is to have many threads, each with a piece of memory for a screen and their own command line information, and to tie one to each of the function keys (F1-F12) to get virtual terminals. This would be a fun feature even while this is still a single threaded system. Way in the future I will read the APIC documentation (possibly HPET also?) to get a preemptive round robin going, but I would like at least a simple memory manager going before I allocate much fixed stuff on the heap (which is everything above the 3 MB mark right now, with the kernel at 1 MB and the system dictionary at 2 MB).

Well, that is enough for today- I have lots of fun things to work on! I love the response you get from adding features to a system like this with quick turnaround and useful results.