 It was used as the directory separator in Classic Mac OS, and was difficult to use in early versions of the newer BSD-based macOS due to code swapping the slash and colon to try to preserve this usage.In most systems it is often difficult to put a colon in a filename as the shell interprets it for other purposes.CP/M and early versions of MSDOS required the colon after the names of devices, such as though this gradually disappeared except for disks (where it had to be between the disk name and the required path representation of the file as in codice_6).