If you copy files, you are dealing with file pointers, such as HDrop, which take up almost no space. And almost no time to execute a copy. If you really had to wait 3 GB to copy to the memory buffer, you would wait a long time, there would be a lot of I / O, and if you did not have a lot of memory, your system would have to use page space, thereby causing even more input-output
You should also understand that unlike a text / HTML / RTF / graphic copy (where the data is actually on the clipboard), the clipboard cannot be used as a security grid. With text, you can copy, then delete the text and paste it to return it. Not so with files. If you copy a file and then delete this file, you cannot paste it. This may seem obvious, but it's important to understand when you use some kind of clipboard manager that allows you to go back and paste previous clips. For example, you can insert a pointer to a file from 3 days ago, but the result will not be the same as 3 days ago. It will be that the file pointer refers to today's disk.