Extracting the folder name and filename from a file path?

How would one extract a filename or a folder name from the path to a a file?

For instance, given a Windows path like:

C:\SomeFolder\SubFolderA\SubFolderB\filename.txt.bak

Or a Unix path like:
\SomeFolder\SubFolderA\SubFolderB\filename.txt.bak

The function =foldername(...) would return "SomeFolder\SubFolderA\SubFolderB" and =filename(...) would return "filename.txt.bak".

The algorithm is quite straightforward, as the filename is always at the right-hand end of the string. So, starting from that end, examine each character in turn (and count the number of characters) until you reach a \ or : The filename can be obtained using RIGHT and the path can be obtained using LEFT, along with the count of characters and the original length of the string.

Hope this helps.

Pete