Cell

A cell is a named drawing made once so it can be stamped many times instead of redrawing the ink.

A chip is not one giant doodle. A via stack, a memory bit, a pad, a whole block — each is a cell. Edit the master and every stamp updates. Forget to name the work and the copies drift apart. The cell list shows names such as INVX1 or pad_vdd. Open INVX1 and you might find a handful of rectangles. Open the top cell and you might find a thousand stamps of that inverter plus a ring of pads. Each stamp is an instance, not a second original. A cell is not a file. Some systems store one cell per file. Graphic Design System II (GDSII) stores many cells in one stream. The idea is the name and the contents, not the disk layout.

This L, with the small square on one corner, is the named drawing. It is drawn once.

Cells nest. A bit cell can sit inside a bank, and the bank inside a chip. That nesting is hierarchy. A regular grid of stamps is an array. If you explode every stamp into raw shapes, you flatten the drawing and lose the single place to edit.

How masters and stamps relate, what a layout is made of, and why the nesting is worth keeping are covered in cells and instances, what is a layout, and hierarchy and flattening.