ResEdit changed what was in the resource fork. With Mac OS X, Apple moved away from forks to extended attributes, now used for quarantine flags and more.
Mac OS 9
The Desktop and Finder illusions rely on files having a type and creator, and an icon association. These were kept in the Desktop Database, and are now the responsibility of Launch Services.
Are still running macOS 10.12.6 (16G29)? Where can you find that build number of macOS? Should it matter?
One of the great hidden features in macOS, xattrs are rarely used by anyone outside Apple, largely because they are so poorly supported by functions calls and tools.
macOS Sierra it is then – but why did Apple choose those names?
If you wanted to mess someone’s Mac up, you could go into their system files and change things around when they were out at lunch.
Already, it is being rumoured that this summer, Apple will change the name of OS X to macOS. Is this just for consistency?
I would like new windows in apps to open in the lower half of the screen. Can El Capitan do that yet?
Old archived files had lost association with the right app. What went wrong?
Among the new features of 9.1 was support for the burning of CDs in the Finder, and Finder support for switching between open windows.
The Eclectic Light Company 