chip8Archive VS Octo

There's also a collection of 90 ROMs, mostly from past Octojams, collected with metadata and source code here: https://github.com/JohnEarnest/chip8Archive

The original CHIP-8 software corpus exists in a copyright gray area, though RCA is profoundly unlikely to exercise its copyright on those materials. There are, however, many programmers today writing new software targeting this platform. The CHIP-8 Archive has a collection of programs which are available under an unambiguous Creative Commons license.

1. Octo, a CHIP-8 assembler: https://github.com/JohnEarnest/Octo

P.S. Octojam 10 runs until 12:00 AM PST on November 1st! See the following if you're interested! https://itch.io/jam/octojam-10

In addition to what other posters suggested, it could be a good idea to try assembly languages as a way to manually work with locations in memory. Something like Octo could be fun if you want to try memory manipulation without worrying about real-world complexities like syscalls and memory alignment. If you want something extra challenging, you could always try x86 / amd64 assembly. Some C compilers even support inline assembly if you want to mix C and assembly.

Yes, Octo is the most used tool to create CHIP-8 programs today. John has a little introduction text for writing in its dialect here: https://github.com/JohnEarnest/Octo/blob/gh-pages/docs/BeginnersGuide.md

I also want to thank you all for all the advice you gave to me and others about CHIP8. It was very helpful to read some posts here ! I also used John Earnest's OCTO a lot for debugging.

The octo FAQ touches on this "pre-xoring" technique, and theres a worked example of doing this data preparation in macros. I've also written varioustools that can handle the xoring for you.

In my own system, Octo[0], I encode programs and their metadata in a similar steganographic fashion in GIF files. As others have noted here, both GIF and PNG offer extension mechanisms and ways to embed "comments", but popular image-sharing sites universally re-encode images and discard this data. The advantage of GIF over PNG (for my purposes) is that I store an arbitrary payload in a fixed-looking image by creating additional frames of animation.

In the past, I've also used a different technique- if you simply concatenate a PNG onto a JAR (which is really just a ZIP archive) you end up with a file that acts like a PNG unless you change the extension to JAR, in which case it acts like a Java executable. This works because the PNG header is at the beginning of the file, while the ZIP header is at the end. Nowadays, though, desktop Java is pretty much dead, so it's a less exciting party trick.

[0] https://github.com/JohnEarnest/Octo