It will help you with calculating the octal value for manipulating file permissions using the chmod command which is typically found on Unix and Linux systems. It's also a good tool for deciphering an octal value.
I re-wrote the BlackBerry 10 version of the app to iOS. Below you'll find two screen shots from the iOS app:
Main view where you can manipulate and see the relation between individual bits and the octal value.
It's also possible to share the octal value with others directly from within the app.