Source Code of Several Atari 7800 Games Released
jadoon88 writes to share a series of old Atari 7800 games that have been unofficially open sourced. "Remember Dig Dug or Centipede or Robotron? They used to be favorites when Atari's 7800 series was still around. Since the era of those consoles is over, and a different world of interactive reality gaming has taken over, Atari has unofficially released source code of over 15 games for the coders and enthusiasts to admire the state-of-the-art (because this is what it was back then). During those times, nobody would have imagined in their wildest dreams the games that Atari's developers floated into the gaming thirsty market and instantly swept across continental boundaries. But things changed soon after that and a company once regarded as one of the most successful gaming console manufacturers and developers faded away in the pages of our technology's hall-of-fame."
Well this is really great and I thank them for finally releasing code from like 40 years ago but what does 'unofficially released source code' mean exactly???
No, but whomever wrote that headline is making a common mistake. The use of the term "open source" tells us that "open source" is apparently no more clear to people than what that movement tried to supplant—free software. While "free software" has an ambiguity problem, that problem is easily resolved by saying the "free" refers to freedoms to run, share, and modify the software, not a reference to price. "Open source" is also widely misunderstood:
but not easily cleared up. As that essay points out, "the explanation for "free software" is simple--a person who has grasped the idea of "free speech, not free beer" will not get it wrong again. There is no such succinct way to explain the official meaning of "open source" and show clearly why the natural definition is the wrong one.".
From what I can tell, there's no permission given to share any of these programs, no permission to modify any of these programs, and no permission to distribute these programs commercially.
The blog poster claims "In an official release, Atari has quoted that the purpose of the release is to give potential developers insight into the Atari's gaming platform so they may possibly build upon the 7800 series." but there is no link to the official release from the copyright holder. Therefore the provenance of this source code is unclear. I would consider these programs to be neither open source nor free software. This looks like an offer to download source code for proprietary software then make the mistake of distributing unauthorized derivative works based on these programs. It might be fun to program new Atari 7800 games, but copyright lasts a very long time and there's too little information to verify what the blogger claims.
Digital Citizen
Perhaps so that accidental execution of a cleared area of memory would break rather than silently execute until it reached something non-zero. On the other hand, the 6502 didn't have any microcode, so opcodes were laid out based on the most efficient way to decode them. This $EA triggered the right combination of steps internally to do nothing. In other words, $EA probably gives them NOP for free. There are lots of unofficial opcodes which do strange things, including NOPs that use more than one byte (so-called double NOPs and triple NOPs).