Key punch

A key punch is a machine for manually entering data onto punch cards. The key punch looked like a small desk. It had a keyboard similar to a typewriter and hoppers for blank and punched cards. Later model key punches printed the value of each column punched at the top of the card. In some cases decks of punched cards were then sent to a second machine called a verifier, which looked a lot like a key punch. Its operator entered the exact same data as the keypuncher, but the verifier machine merely checked to see if the data was the same. Valid cards had a small notch punched on the right hand edge.

Key punch machines could be programmed by wrapping a specially punched IBM card around a small metal drum. The patterns of holes on the drum card could control tabbing and automatic duplication of fields from the previous card, among other things.

Post-WW II IBM Key punches for 80-column cards

Key punches made a distinctive "chunk, chunk" sound as characters were punched.

IBM 024

Basic keypunch with no printing.

Logic was 25L6 vacuum tubes and relays. The circuits used 150VDC, which was present in the keyboard (you did NOT want to spill a drink on it!)

IBM 026

This key punch could print the encoded character above each column. There were two popular versions with slightly different character sets. The scientific version printed parentheses, equal sign and plus sign in place of four less frequently used characters in the commercial character set: percent, lozenge, pound, and ampersand. The character was printed using a 5x7 dot matrix array of wires; the ROM from which it derived the shape of the character was a metal plate with space for 2240 pins (if the dot was not to be printed in a given character, the pin was machined off). By correctly positioning the plate and pressing it against one end of the array of printing wires, only the correct wires were pressed against the ribbon and then the punched card. (This printer mechanism was generally considered by IBM Customer Engineers to be unreliable and difficult to repair. One of the most common problems was wires breaking in the tightly curved narrow tube between the ROM plate and the ribbon - extracting the fragments and replacing the bundle of 35 wires was very tedious!)

Logic was 25L6 vacuum tubes and relays. The circuits used 150VDC, which was present in the keyboard (you did NOT want to spill a drink on it!)

IBM 029

Introduced with System 360, the 029 had new character codes for parentheses, equal and plus as well as other new symbols used in the EBCDIC code. The IBM 029 printed on the top of the card the punched character using the same kind of mechanism as the IBM 026.

Logic was diodes on SMS cards and relays running on 48VDC.

For applications that required the filling-in of specific fields within the punched cards, IBM 024, 026, and 029 keypunches, with the optional Program Drum feature installed, could be programmed (using another punched card, of course) to automatically advance to the beginning of each field, only accept certain character types within the field, duplicate a field, and so on. A switch permitted selection of one of two programs, if the optional Second Program feature was installed (program 1 in top six rows and program 2 in bottom six rows [4,5,6,7,8,9).

The program card was called the drum card because it was mounted on a small metal drum that was as high as the card and whose circumference was equal to the length of the card. The drum is visible in the above image behind the window in the upper/center section of the machine. The central cover would be tilted toward the operator, a locking lever released, and the drum then removed/replaced. The holes in the drum card were sensed by an array of starwheels that would cause levers to rise and fall as the holes in the drum card passed beneath the starwheels, activating electrical contacts. The drum card was punched with characters that controlled its function as follows:

Function	Program				Usage
Function	#1	Char.	#2	Char.	Usage
Field Definition	12	&	4	4	Punch in every column of a field, except the first (left)
Start Automatic Skip	11	-	5	5	Punch in first (left) column of field(s) to skip
Start Automatic Duplication	0	0	6	6	Punch in first (left) column of field(s) to duplicate
Alphabetic Shift	1	1	7	7	Punch in a column to shift keyboard to Alphabetic mode
Left Zero Print	2	2	8	8	Punch in a column to force printing of leading zeros and signs
Print Suppression	3	3	9	9	Punch in a column to suppress printing

Many programming languages, such as Fortran, the RPG programming language or the IBM Conditional assembly language, coded operations in specfic card columns, such as 1, 10, 16, 36, and 72. The drum card for such a setup would be coded as:

1.......10........20........30........40........50........60........70........80 1AAAAAAAA1AAAAA1AAAAAAAAAAAAAAAAAAA1AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA &&&&&&&&

Note: "Field Definition" (12) and "Alphabetic Shift" (1) prints as an A. If Program #2 codes were punched, invalid characters could be generated that the printer did not know how to print, some of which could even damage the printer! Thus it was usually a good idea to turn off printing when duplicating a drum card on the 026 or 029.

IBM 129

The transistorized IBM 129 Card Data Recorder's primary advantage over the 029 was that it featured an electronic 80 column buffer to hold the card image. When using earlier keypunches a keystroke error required the card to be ejected by pressing the Release and Register keys, the error corrected by pressing the Duplicate key until the wrong column was reached, typing the correct data for the rest of that card, then pressing the Release key and manually removing the bad card from the output card stacker before it was placed in the deck (this required some practice, but quickly became an automatic action that you no longer had to think about). With the 129 a keystroke error could be erased by pressing the Backspace key and re-keyed. The entire 80 column card was punched in one operation when the Release key was pressed.

Logic was in SLT modules.

A secondary advantage was that the speed of the keying operation was not limited by punching each column at the time of the keystroke.

The 129 could store several programs in its memory, selectable by a rotary switch (no drum card required).

Other formats

Univac made key punches for their 90 column cards. These stored the user's keystrokes, then punched the entire card all at once (and hence allowed correction of errors before the card was punched).

In the early 1970s, IBM introduced the System/3 family of low-end business computers which featured a new punch card format that was smaller and stored 96 characters. Instead of the rectangular punches of the 80-column card, the new cards had tiny (1 mm), circular holes much like paper tape. Data was stored in six-bit binary-coded decimal code, with three rows of 32 characters each, or 8-bit EBCDIC, with the two extra holes located in the top rows. Special 96-column key punch/verifiers were sold to accompany this system.

External links

IBM hardware | User interface techniques | History of computing

Gourt Home::Gourt :: Key punch