I just started using Xcode 3 and I noticed some of my apps had the "d" (directory) attribute. At first I thought it was a mistake until I did some further research. It seems that some apps really ARE directories, the directory contains all the files the program needs to run. When you view one of these apps in Finder, it will appear as a single file and will run when you double click on it or tell it to open from the context menu. However, when you view it from the terminal window (the command is ls -la) it will have the "d" attribute and you can change directories (the command is cd directoryname) and see all the parts of that particular program. In the case of Xcode Cocoa applications, it has the .nib file that you made in Interface Builder plus some other stuff.