Numeric values have one hole in a column and are straightforward to sort, but how about alphabetic characters? In addition to the ten numeric rows 0-9, punched cards also have two additional “zone” rows (11 and 12). The diagram below shows the encoding; a letter combines a digit punch (1-9) with a zone punch (a hole in 0, 11 or 12). Confusingly, row 0 is used both as a zone and a digit.
With this encoding, a sorter can perform an alphabetical sort in two passes. The first pass sorts on the numeric rows, putting cards into bins 1 through 9. These bins are gathered up in order and the cards are sorted a second time. For the second sort, the zone rows (0, 11 and 12) are read and the digit rows are ignored. The result is A through I sorted in bin 12, J through R in bin 11, and S through Z in bin 0. For multiple-character fields, the process is repeated for each column.
Control switches on the sorter select a numeric or zone sort. The photos below show these controls on the Type 80 (top) and 83 (bottom) sorters. The Type 80 sorter has a round commutator with tabs that are moved in or out to select which rows to use; the red tab selects a zone sort. The Type 83 sorter has pushbuttons to select rows, as well as a switch to select different types of sorting (Numeric, Zone, or Alpha).
In 1925, IBM introduced its first horizontal card sorter, the Type 80. This sorter became very popular with 10,200 units in use by 1943. IBM continued to support this card sorter until 1980, a remarkable lifespan of 55 years.
The Type 80 sorter performed useful data processing with electromechanical technology without the benefits of transistors or even vacuum tubes. The Type 80 sorter used a relay to latch the electromagnet on for the duration of the card; this is the extent of its “intelligence”.
Even though it was electrically simple, the sorter was a piece of precision machinery. It sorted 450 cards per minute, so the chute blades must pop down and up more than 7 times per second. Any timing error could result in a mis-sorted card or could cause the blade to nick the edge of the card.
IBM’s next sorter model was the Type 82, able to sort 650 cards per minute, and renting for 55 dollars per month. At the faster speed, an electromechanical relay wasn’t fast enough to control the magnet, so vacuum tubes were used.
The next sorter model, the Type 83, was introduced in 1955. It could sort 1000 cards per minute and rented for 110 dollars per month. This sorter used a much more advanced technique for processing cards: instead of selecting the card chute at the instant a hole was detected, the 83 sorter read all the holes in the column before selecting a card chute. This allowed the Type 83 sorter to perform tasks that were impossible with the previous sorters, such as rejecting erroneous cards that had multiple holes in one column.
IBM’s most advanced sorter was the Type 84, introduced in 1959 and produced until 1978. This sorter replaced the wire brush with a photoelectric sensor and used solid state technology. A vacuum feed grabbed cards more effectively. With these improvements, it could process 2000 cards per minute, over 30 cards per second flying through the sorter.