Take the prosaic problem of the great department store. Every time a
charge sale is made, there are a number of things to be done.. The
inventory needs to be revised, the salesman needs to be given credit
for the sale, the general accounts need an entry, and, most important,
the customer needs to be charged. A central records device has been
developed in which much of this work is done conveniently. The
salesman places on a stand the customer's identification card, his own
card, and the card taken from the article sold - all punched cards.
When he pulls a lever, contacts are made through the holes, machinery
at a central point makes the necessary computations and entries, and
the proper receipt is printed for the salesman to pass to the
customer.
But there may be ten thousand charge customers doing business with the
store, and before the full operation can be completed someone has to
select the right card and insert it at the central office. Now rapid
selection can slide just the proper card into position in an instant
or two, and return it afterward. Another difficulty occurs, however.
Someone must read a total on the card, so that the machine can add its
computed item to it. Conceivably the cards might be of the dry
photography type I have described. Existing totals could then be read
by photocell, and the new total entered by an electron beam.
The cards may be in miniature, so that they occupy little space.