How do punch card readers work

The IBM could have been used in either the or census. By see below much faster punches were available, e. This machine is from the s. The card had 80 columns, to hold 80 digits. Punching the X-key, above the digits, indicated minus.

We still find many data files in commerce today that are 80 characters wide. Alphabetic characters could be entered by punching the top key and a digit in the same columns for A-I, the X-key and gave J-R, and 0 and gave S-Z. Hollerith's systems opened up an important new field of employment to women, starting with the Census. IBM Duplicating Punch Note: there was also a later-model Port-A-Punch in The Type 10 Card Punch similar to the one shown above was listed in a "" sales manual as an electric, non-duplicating, numerical card punch available in 80, 66, or column models with skip bar.

IBM Punch Cards Prior to , IBM cards were punched with round holes; originally in 20 columns, but by the late s, 45 columns, as shown in this New York University registration card, reproduced from Baehne [ 91 ]. All punches introduced prior to , including the , used round holes and 45 or fewer columns. Beginning in , IBM cards had rectangular holes 80 columns across, as shown in this Iowa State University registration card, also reproduced from Baehne [ 91 ].

All punches introduced after , including the Types , 31, and 32 and possibly the , and of course the later , , and related models, produced column cards. This was IBM's first punch with automatic feeding and ejecting mechanisms; it was marketed until there was also an model that lacked duplicating feature.

The punching is done magnetically, and information from one card can be transferred automatically to another by a duplicator. The keyboard contains 12 punching keys, one for each row on the card. There are also space and eject keys.

A master program card can be used to control automatic tabbing and duplication of fields. A skilled operator could punch cards per hour on this model. Once a card is completed, or the Return key is pressed, the card technically "stores" that information. Because each card only holds so much data, if you write a program using punch cards one card for each line of code , it requires a stack of punch cards.

To load the program or read punch card data, each card is inserted in a punch card reader to input data from the card into a computer. As the card is inserted, the punch card reader starts on the top-left side of the card, reading vertically from top to bottom.

After the card reader has read a column, it moves to the next column. As the reader read the information, it would be written to a computers memory.

After all cards were loaded into memory, the computer would be instructed to execute the code. If information was outputted printed , it would be outputted as punch cards. The largest punch card program was from the s SAGE air defense system, which used 62, punched cards around 5 MB of data. In the picture below, a woman stands next to the punch cards used in this program. One of the biggest fears of users dealing with punch cards was dropping the punch cards.

If these cards were dropped or got out of order, it could take days or weeks to get the program back in order. In some cases, it wouldn't be possible to put the program back into order. Most of the later punch cards printed at the top of the card what each card contained.

For these cards, you could examine the top of the card to see what was stored on the card. If an error was noticed on the card, it would be re-printed. If no data was printed at the top of the card, the human would need to know what number represented and manually translate each column.

If you are familiar with modern computers, this would be similar to knowing that binary and are equal to and , which in ASCII put together spells hi. Punch cards are known to be used as early as for controlling textile looms. For example, Joseph Marie Jacquard used punch cards to create a self-portrait woven in silk. The cards were later used to store and search for information in by Semen Korsakov.

Later in , Herman Hollerith developed a method for machines to record and store information on punch cards to be used for the US census. He later formed the company we know as IBM.