[cynwoody]

Mac OS versions prior to OS X used ':'.

Mac OS X, initially released on 24 March 2001, uses '/', like other Unix-derived systems.

Also, like other unices, OS X uses '\n' as the line ending. Prior Mac OSs used '\r' as the line ending. Windows uses '\r\n'.

[pjmlp]

In A/UX you could use both.

[hestefisk]

Similar, HFS+ used to provide the option for case insensitivity. Both things were built in for legacy support reasons during the transition from OS 9 to X, as with Carbon.

[zwily]

Macs still come with case insensitivity on by default.

[codesnik]

but in Finder you can use "/" in filenames, and can't use ":". They got swapped if you look on the file from Terminal.