Why are filenames in CP/M | *DOS limited to 8 characters (excluding the 3 letter extension)?

Also, why did older computer require physically switching off the computer (anyone remember the 'It is now safe to switch off your computer' message?) instead of the ACPI shutdown virtually all modern OS and machines have nowadays?

Question

Why are filenames in CP/M | *DOS limited to 8 characters (excluding the 3 letter extension)?

Also, why did older computer require physically switching off the computer (anyone remember the 'It is now safe to switch off your computer' message?) instead of the ACPI shutdown virtually all modern OS and machines have nowadays?

espex · Answer

The filename was limited by the use of the FAT file system. As for the power off issue, the ATX motherboards had not yet been produced and thus the power supply could not "switch off" the system. You had to wait for the "safe" message in order ensure that all of the OS processes had completed, again since the system couldn't monitor itself.

rsmith6559 · Answer

Remember that filenames are one field of the metafile (directory).  So if that was the size that the designers of the filesystem decided, oh well!

BTW, currently, most filesystems limit names to 255 bytes, not characters.

rsmith6559 · Answer

Here's an interesting series on Unix/Linux filesystems: http://www.cyberciti.biz/tips/understanding-unixlinux-file-system-part-i.html