This post describes a simple trick to enable filename extensions to be displayed at all time in Finder.
I like to know and see what is the filename extension - because sometimes I would like to change them to different type.
By default, Mac OS X will not display the file extensions for known file type, such as .pdf. This could cause confusion because you might see some files that has filename extensions, but some don't.
In order to set Finder to display all filename extensions, go to Finder -> Preferences. Click “Advanced”.
Ensure “Show all filename extensions” is checked.
What you have now is all files will be displayed with filename extensions.
