Lahrs

To be fair, I don't even understand how zip files work, so I believe that will be my next Google search. It is all 1's and 0's and if you shrink them down, they have to go somewhere. That is just my thought process at the moment, and I need to read up and get informed. I do appreciate your reply. While the compression still wracks my brain, I do believe I understand the on-the-fly decompression into memory, and I assume that is why the game still plays at full speed.

This isn't a question on to how to make a .chd file but what is actually going on with it. For example, I have a Dreamcast ROM of NBA Hangtime, the cue/bin file size is roughly 1.1GB. I turned it into a .chd file, and it's down to 247mb. I run it through Flycast, and it runs just as well, loads up just as fast, and plays exactly like the cue/bin file but at 1/4 the HD space. It seems as long as the emulators themselves can play a .chd file, there is every reason to convert them. Am I missing something? How does a file reduce its size to 1/4 without losing anything? Amazing, but baffling.