In many data processing facilities the punched cards were sent to a second machine, called a verifier, that looked similar to a key punch. The verifier operator entered the exact same data as the keypunch operator and the verifier machine then checked to see if the punched data was the same. Successfully verified cards had a small notch punched on the right hand edge. There was a great demand for key punch operators, usually women, who worked full-time on key punch and verifier machines.
IBM keypunches such as the 024, 026 and 029 provided for the mounting of a program (or drum) card that controlled various functions, such as tabbing and automatic duplication of fields from the previous card. The later 129 used electronic circuit cards to electronicly store simple programs written by the keypunch operator.
Herman Hollerith's first device for punching cards from the 1890s used a pantograph to link a punch mechanism to a guide pointer that an operator would place over the appropriate mark in a 12 by 20 matrix to line up a manual punch over correct hole in one of 20 columns, In 1901, Hollerith patented a mechanism where an operator pressed one of 12 keys to punch a hole, with the card automatically advancing to the next column. This first generation Type 001 key punch used 45 columns and round holes. In 1923 CTR (renamed IBM in 1924) introduced the first electric keypunch, a similar looking device where each key closed an electrical contact that activated a solenoid which punched the hole. Later IBM key punches included the Type 016 Motor-Driven Electric Duplicating Key Punch (1929), the Type 31 Alphabetical Duplicating Punch (1933) ,and the Type 32 Alphabetical Printing Punch (1933). See Early Card Punch Machines at Columbia University Computing History.
The IBM 024 Card Punch and IBM 026 Printing Card Punch (photo) were announced in 1949. They were almost identical, with the exception of the printing mechanism.
The heart of the 024 and 026 keypunches was a set of twelve precision punches, one per card row, each with an actuator of relatively high power. Punch cards were stepped across the punch one column at a time, and the appropriate punches were activated to create the holes, resulting in a distinctive "chunk, chunk" sound as columns were punched.
The 026 could print the punched 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!)
Raymond Loewy, industrial designer of "streamlined" motifs who also designed railway passenger cars of the 1930s and 1940s, did the award winning external design of the 026/024 series for IBM. Their heavy steel construction and rounded corners (photos) indeed echo the industrial Art Deco style.
Verifier companion to the IBM 024 Card Punch and IBM 026 Printing Card Punch. Physically, the IBM 056 verifier was visually similar to the 026 keypunch except for the presence of a red error lens located in the machine cover lower center.
The IBM 056 verifier utilized most of the same mechanical and electrical components as the 024/026 keypunch machines with the exception of the punch unit and print head. The punch unit had sensing pins in place of the punches which were driven through the holes where present, and prevented from full travel where there was no hole present as each card column was stepped by. The holes sensed or not sensed would trip a contact bail when the configuration was other than that entered by the verifier operator. This stopped the forward motion of the card, and presented a red error light on the lower center of the machine cover. The notching mechanism was physically located in the area occupied by the print mechanism on a 026 printing keypunch. It had a solenoid which drove the notching mechanism, and another that selected the top notch punch or end of card punch.
When an operator keying data to be verifed encounted an error the operator was given a second and third try to re-enter the data that was supposed to be in the field. If the third try was incorrect an error notch was put on the top of the card over the column with the error and the "OK" punch at the end of the card was not enabled. It should be noted that the data in the card could actually be correct upon occasion as the verifier operator was capable of making errors as well as the keypunch operator. However with three tries, the operator was less likely to repeatedly make the same error. Some verifier operators were able to guess the error on the card created by the previous keypunch operator defeating the purpose of the verify procedure, and thus some machines were altered to allow only one entry and error notched on the second try.
Cards with error notches were re-punched (using an 024 or 026) usually by "duplicating" to the column in error, then entering the correct data. The "duplicating function was accomplished by feeding the card through the punch station without punching it. At the next station sensing pins read the holes present in the original card and transferred the data to the punching station and into a blank card. Columns with errors were corrected instead of being duplicated. The corrected card was then verified to check the data again and be "OK notched"
This was an IBM 024 where the 024 keyboard was replaced by an IBM electric typewriter, permitting the same text to be typed and punched.
This was an IBM 026 where the 026 keyboard was replaced by an IBM electric typewriter, permitting the same text to be typed and punched.
Introduced with System/360 in 1964, 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 was mechanically similar to the IBM 026 and printed the punched character on the top of the card using the same kind of mechanism as the 026. The use of tubes (and high voltages) was dropped with the 029.
The 029's logic consisted of wire contact relays on earlier models and reed relays and diodes on SMS cards for later models. All ran on 48VDC. A common additional feature made available (at addional cost) was the leading zeros feature. This was delivered by an additional set of four SMS cards. The field was programmed for leading zeros using the program card on the drum. If it was (say) a six digit field, the operator only had to key in the actual value (for example 73). The feature would then fill the field by punching the leading four zeros, followed by the 73, in effect right justifying the field. Thus: 000073.
Verifier companion to the IBM 029 Card Punch.
Logic was in SLT modules.
A secondary advantage of the 129 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 six programs in its memory, selectable by a rotary switch (no drum card required).
The program card was also 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:
|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 specific card columns, such as 1, 10, 16, 36, and 72. The drum card for such a setup would be coded as:
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.
Drum card programs could automate certain tasks, such as "gang punching", the insertion of a constant field into each card of a deck of cards. For amusement, drum cards could even be set up to play music by gang-punching "noisy" characters (characters represented by many holes, usually special characters) and "quiet" numbers and letters in rhythmic patterns.
IBM, in the early 1970s, introduced the System/3 family of low-end business computers which featured a new, smaller sized, punch card format with 96 columns. Key punches and verifiers were made for these 96-column cards.