Apple originally designed the iconic trash can icon on the early Macintosh operating systems to actually bulge outward when it contained deleted files, visually indicating that the bin was full of garbage.

A trash can that changed when it was full

Early Macintosh icons had to do more than decorate the screen: they helped users understand what the computer was doing without reading a command. The trash can made deletion tangible. Dragging a file onto it was like dropping paper into a wastebasket, and the icon’s fuller, bulging appearance gave the computer a visible second state: something was inside.

That small change illustrates a key interface-design problem. A symbol must be recognizable at a glance, even when it is drawn from a limited number of pixels. Changing the same can rather than introducing a new symbol let users connect the full state directly to the empty one. It also made the computer’s status visible without opening a folder or checking a message.

The icon and the copyright dispute

Apple’s later legal fight with Microsoft and Hewlett-Packard concerned the copying of elements of the Macintosh-style graphical interface. The trash can was part of that visual vocabulary, but the dispute was broader than a claim over one isolated icon. That distinction matters: copyright can protect a particular graphic’s expression, while the general idea of using a wastebasket to represent deleted files is a design concept.

The enduring cleverness of the full-bin image is its economy. A slight visual change communicates a consequence—deleted files are waiting in the trash—before the user takes another action.