Thread: What actually happens when a file is deleted ?

Hi !!
I might get flamed for asking this but I was wondering as to what actually happens when a file gets deleted ? Is it removed off the hard disk or is it converted in an unreadable format ? Because I have seen that many a times a deleted file can be retrieved using some trick. Is some advanced algorithm converts the file in an un readable format when, say in a windows environment, the file is put in recycle bin and then deleted or deleted by just pressing the delete button ? Is the method of deletion different in Windows and Unix ?

I would be etremely thankful if someone could answer the question.