There may remain some small files such as preferences and help files left lying about but the main programme is certainly removed just by dragging it to the trash and, of course, emptying the trash afterwards. If the file loaded however was a system file, such as a system upgrade, a font, printer driver, etc or something that interfaces directly witht the system then it may also have left a receipt file. This I think is to allow the Software Update facility to know what is loaded and so what would needs updating.
Whilst the chucking of a program to the trash removes the program it does not remove all traces of it having been there and while the remnants, such as preferences, help files and sometimes receipts etc, take up very little space if you were wanting to delete all traces then using the find facility to find locate them is easy enough.
Andy
