System 5

System 5, strictly speaking, was a non-existent version of the Mac OS.

Closely related to "System 5" is System Software 5.0, a software bundle which included System 4.2, Finder version 6.0, MultiFinder 1.0 and LaserWriter version 5.0.

No version of the System file was ever numbered "version 5".

Refer to

 * System 4.2
 * System 4.3

Sources and References

 * The Mac 512: System version numbering scheme