The Mac OS X Mountain Lion Clipboard
Before you start moving your files around in Mountain Lion, you need to understand the Clipboard. The Clipboard is a holding area for the last thing that you cut or copied — text, a picture, a portion of a picture, an object in a drawing program, a column of numbers in a spreadsheet, any icon (except a disk), or just about anything else that can be selected.
In other words, the Clipboard is the Mac’s temporary storage area.
Most of the time, the Clipboard works quietly in the background, but you can ask the Clipboard to reveal itself by choosing Edit→Show Clipboard. This command summons the Clipboard window, which lists the type of item (such as text, picture, or sound) on the Clipboard — and a message letting you know whether the item on the Clipboard can be displayed.
As a storage area, the Clipboard’s contents are temporary. Very temporary. When you cut or copy an item, that item remains on the Clipboard only until you cut or copy something else. When you do cut or copy something else, the new item replaces the Clipboard’s contents, and the newcomer remains on the Clipboard until you cut or copy something else. And so it goes.
Whatever is on the Clipboard heads straight for oblivion if you crash, lose power, log out, or shut down your Mac, so don’t count on it too heavily or for too long.
The Clipboard commands on the Edit menu are enabled only when they can actually be used. If the selected item can be cut or copied, the Cut and Copy commands in the Edit menu are enabled. If the selected item can’t be cut or copied, the commands are unavailable and are dimmed (gray).
If the Clipboard is empty or the current document can’t accept what’s on the Clipboard, the Paste command is dimmed. Finally, when nothing is selected, the Cut, Copy, and Clear commands are dimmed.
Icons can’t be cut; they can only be copied or pasted. So when an icon is selected, the Cut command is always gray.