The numbers that are stored or sorted in punch-card machines may be of any size up to 80 digits, one in each column of the punch card. In doing arithmetic (adding, subtracting, multiplying, and dividing), however, the largest number of digits is usually 10. Beyond 10 digits, we can work out tricks in many cases.
TYPES OF PUNCH-CARD MACHINES
The chief IBM punch-card machines are: the key punch, the verifier, the sorter, the interpreter, the reproducer, the collator, the multiplying punch, the calculating punch, and the tabulator. Of these 9 machines, the last 6 have plugboards and can do many different operations as a result.
There is a flow of punch cards through each of these machines. The machines differ from each other in the number and relation of the paths of flow, or card channels, and in the number and relation of the momentary stopping places, or card stations, at which cards are read, punched, or otherwise acted on. We can get a good idea of what a machine is from a picture of these card channels.
Key Punch
We use a key punch ([Fig. 5]) to punch original information into blank cards. In the key punch there is one card channel; it has one entrance, one station, and one exit. At the card station, there are 12 punching dies, one for each position in the card column, and each card column is presented one by one for punching. The numeric keyboard ([Fig. 6]) for the key punch has 14 keys:
One key for each of the punches 0 to 9, 11, and 12,
A space key, which allows a column of the punch card to go by with no punch in it,
A release key, which ejects the card and feeds another card.
