Tub file

The tub file was a technique used in the punched card era to speed generation of data files.

This technique was an early form of random access memory.

A wholesaler might have a tub file with cards for frequent customers and for each inventory item.

The resulting deck could then be run through a tabulating machine to produce an invoice.

In this example item cards also provided inventory control, since each card presumably represented one item in stock, so it was simple to check availability and schedule reordering.