After researching this question, I've concluded that there are two answers. The first answer is that there isn't anything special about 132 columns. In particular, early printers used an astoundingly large variety of line widths including 50, 55, 60, 70, 73, 80, 88, 89, 92, 100, 118, 120, 128, 130, 136, 140, 144, 150 and 160 characters.2 This shows there was no strong technical or business reason to use 132 columns. Instead, 132 columns became a de facto standard due to the popularity of the IBM 1401 computer and its high-performance 1403 line printer, which happened to print 132 columns.
The second, more interesting, answer is that a variety of factors in the history of data processing, some dating back a century, led to standardization on several sizes for printed forms. One of these sizes became standard line printer paper holding 132 columns.
The first printer to use 132 columns appears to be the IBM 1403 line printer, which provided output for the IBM 1401 business computer. The IBM 1401 was the most popular computer of the early 1960s, largely due to its low price. Earlier computers had been limited to large corporations due to their high cost; the IBM 705 business computer rented for $43,000 a month (almost $400,000 in current dollars). But the IBM 1401 could be rented for $2500 per month, opening up the market to medium-sized businesses that used it for payroll, inventory, accounting and many other business tasks. As a result, over 10,000 IBM 1401 computers were in use by the mid-1960s.
The IBM 1403 printer in front of the popular 1401 business computer (right) and 729 tape drives (left).
Now I'll discuss the history that led up to 132 columns on 14 7/8" paper. The key actor in this story is the electric accounting machine or tabulator. While these machines are mostly forgotten now, they were the cornerstone of business data processing in the pre-computer era (history). Tabulators date back to the 1890 census when Herman Hollerith invented these machines to tabulate (i.e. count)6 data stored on punch cards. Later tabulators used relays and electromechanical counters to sum up values, were "programmed" for different tasks by a plugboard of wires, and could process 150 punch cards per minute.
The IBM 403 electric accounting machine. Note the programming plugboard at left with yellow wires. The printer carriage is on top. Cards are fed into the hopper to the left.
By 1943, tabulators were popular with businesses and governments; IBM had about 10,000 tabulators in service. These machines were complex, able to handle conditionals while adding or subtracting three levels of subtotals and formatting their alphanumeric output. Accounting machines were used for a wide variety of business data processing tasks such as accounting, inventory, billing, issuing checks, printing shipping labels or even printing W-2 tax forms. While these machines were designed for businesses, tabulators were also pressed into service for scientific computation in the 1930s and 1940s, most famously for nuclear bomb simulations during the Manhattan Project.
The earliest tabulators displayed the results on mechanical counters so an operator had to write down the results after each subtotal (details). The development of the tabulator printing unit in the 1920s eliminated this inconvenient manual step. One popular printing tabulator was the IBM 285, introduced in 1933. This machine printed values using 3 to 7 "print banks", where each bank consisted of 10 numeric type bars.7 The output below shows 7 column-output, generated by a 285 tabulator with 7 print banks.
Output from the IBM 285 Electric Accounting Machine, showing its 7 columns of counter output. This output is standard typewriter spacing (6 lines per inch), double-spaced. Headings are pre-printed on the form, not printed by the tabulator.
The character spacing was 5/32" (a value that will be important later), yielding columns 1 7/8" wide. This spacing was about 50% wider than standard typewriter spacing (10 characters per inch) even though the tabulator used standard typewriter line spacing (6 lines per inch). As you can see from the output above, this caused large gaps between the characters. So why did the accounting machine use a character spacing of 5/32"? To understand that, we have to go back a decade.
Early IBM punch cards had 45 columns with round holes spaced 5/32" apart.8 The image below shows one of these cards. Each column contained one hole, representing a digit from 0 to 9. One machine used with punch cards was the "interpreter". It read a card and printed the card's contents at the top of the card above the holes. The interpreter used a 45-column print mechanism with type bars spaced 5/32" apart to match the holes.
An IBM 45-column punch card from the early 1920s. This card used round holes, unlike the rectangular holes on "modern" 80-column punch cards. From Electric Tabulating Machines.
In 1928, IBM introduced the "modern" punch card, which held 80 columns of data (below). These cards used rectangular holes so the holes could be closer together (0.087" spacing). However, IBM kept many of the mechanisms designed for 45-column cards, along with their 5/32" spacing. The result was mismatched products like the IBM 550 Interpreter (1930) that read an 80-column punch card and printed 45 characters at the top of the card. As a result, the characters didn't line up with the holes, as you can see below.9 Likewise, The 285 accounting machine used a type bar printer with 5/32" spacing, even though it used 80-column cards.
The IBM 550 card interpreter read data punched into an 80-column card and printed 45 columns of that data at the top of the card.
The IBM 285 tabulator could only print digits, but in 1934, IBM introduced the 405, a tabulator that could print alphanumeric information, followed by the improved 402 accounting machine in 1948. Alphanumeric output greatly expanded the uses of the tabulator, as it could print invoices, address labels, employee records, or other forms that required alphanumeric data. The IBM 405 had 88 type bars that moved vertically to print a line of output (below).18 Note the gap for a ribbon guide between the two blocks of type bars.
The IBM 405 accounting machine printed with type bars: 43 alphanumeric ("alphamerical") type bars on the left, and 45 numeric-only type bars on the right. From Electric punched card accounting machines.
The figure below shows sample output from a 405 tabulator, showing alphanumeric characters on the left side. As with the earlier tabulators, the 5/32" character width resulted in widely separated characters. Note that the headers and boxes were not printed by the tabulator, but were pre-printed on the form.
At first forms were hand-fed sheets of paper, but for convenience these were soon replaced by continuous-feed forms.12 To keep forms from slipping out of alignment, holes were added along the sides so forms could be fed by pin-feed or tractor-feed mechanisms. These forms often used a removable 1/2" perforated strip on each side containing the feed holes.22 Thus, the hole-to-hole width was 1/2" less than the overall width, and the printable region was 1" less than the overall width.
Standard form widths, from the 402 manual, page 151.
The 402's 88 character output fit exactly onto a 14 7/8" wide form, while also being a multiple of 5/32" (hole-to-hole).17 I believe that this was the reason that 14 7/8" paper became a standard. This width is the dimension of standard green-bar line printer paper still used today, so this dimension is very important. Note that this paper size became a standard before commercial computers even existed.
The successor to the IBM 402 accounting machine was the IBM 407 accounting machine, introduced in 1949. The most important feature from our perspective was the move from type bars to type wheels. Each type wheel had 47 characters (letters, numbers and symbols) around the circumference and rotated at high speed to print the correct character.19 The tabulator used 120 of these wheels to print a line of 120 characters.
Type wheel from an IBM 407 accounting machine.
The narrow type wheels enabled the 407 to print 10 characters per inch (standard typewriter pica pitch). The output below shows how the tabulator could issue checks using pre-printed forms. Note that the 407's output looks like normal typing compared to the widely spaced characters of the earlier 405 and 402.
Sample output from an IBM 407 accounting machine. Character spacing is much more natural than the earlier 402 output. Sprocket-fed forms are now common. Figure 128 from Manual of Operation.
The 407 operating manual described how to design forms for the 407,20 and listed eleven standard form sizes (below).21 Despite the switch from 5/32" characters to much narrower 0.1" characters, most of the new standard form widths matched the earlier 402 widths (indicated in green). Many of the previous strange form widths (such as 17 25/32") were dropped, but 13 5/8" and 14 7/8" were preserved, which will prove important.
Standard widths for forms for the IBM 407. From 407 Operating Manual page 187.
Finally we arrive at the 1403 line printer (1959). This printer supported line widths of 100 character, 120 characters, and 132 characters at 10 characters per inch. The 120 character line is obviously useful for backward compatibility with the 407. But what about 132 characters?
The IBM 1403 printer generating a Mandelbrot set on standard 14 7/8"×11" green-bar paper. The IBM 1401 computer is at the left.
To summarize my hypothesis,28 the 132-character line on 14 7/8" wide paper has its roots in the dimensions of punch cards over a century ago. IBM's early 45-column punch cards resulted in the creation of a printing mechanism with a wide character spacing of 5/32" to match the punch card hole spacing. Even though IBM moved to 80-column cards in 1928, accounting machines continued to use 5/32" characters in the 1930s and 1940s. This resulted in standardized form widths, most importantly 14 7/8" which fit a line of 88 characters. In 1949, IBM's tabulators moved to a standard 10 characters per inch spacing. With that character size and 14 7/8" paper, a 132-character line is natural, and this was implemented on the IBM 1403 printer in 1959.
Because the 1403 printer was wildly popular, 132 character lines on 14 7/8" paper became a de facto standard supported by many other companies. This is why even though punch cards are long obsolete, you can easily buy 14 7/8" green-bar line printer paper to this day.
I announce my latest blog posts on Twitter, so follow me at @kenshirriff for future articles. I also have an RSS feed. I've written about accounting machines before, here and here, if you want to learn more. Thanks to Dag Spicer and Sydney Olson (CHM) and Max Campbell (IBM Archives) for research assistance.
It's interesting to look at the history of printers and their assorted line widths.
IBM kept old printing technology around for decades. The print mechanism from the 407 (1949) was reused in the IBM 716 and 717 printers for the IBM 700 series vacuum tube mainframes (1952+) and the IBM 7000 series transistorized mainframes (1958+). The IBM 407 was also used as an output unit for the IBM 650 drum-based computer (1955) and IBM 305 RAMAC disk-based computer (1956). The IBM 1132 printer for the low-end IBM 1130 computer (1965) also used the 407's print mechanism.
The RAMAC system (1956) used the IBM 370 printer (unrelated to the later IBM System/370 mainframe), which printed 80 character lines at 10 characters per inch. This printer was very slow; it took about 2 seconds to print a line using a single octagonal typestick (manual).
In 1970, IBM introduced the IBM System/370 along with the IBM 3211, a new high-speed (2000 lines per minute) line printer. This printer had 132 columns or optionally 150. It was similar to a chain printer except it used a train of character slugs.
I don't have as much information on non-IBM printers, but in 1954, Remington Rand introduced the first high-speed drum printer, the "High Speed Off Line Printer System" for the UNIVAC computer. This printer produced 600 lines per minute at 130 characters per line. The printer used 18 kW of power and was cooled by 8 gallons per minute of chilled water (details, details). As far as other manufacturers, Analex produced a 120-column line printer. Bull had a printer with 80 print bars and a 92-character alphabetical printer Samsatronic had a 140-character dot matrix printer in the 1950s. Burroughs introduced a fast (1000 line per minute) dot matrix printer (called a wire printer) in 1954 that printed 100 character lines. The Burroughs 220 High-Speed Printer System (1959) used a drum to produce 120 character lines at 1225 lines per minute.
Confusingly the word "tabulator" was used for two totally different types of machine. Originally, a "tabulator" was a person, "one who tabulates, or draws up a table or scheme" (OED, 1885). The first type of machine using the name "tabulator" was Hollerith's punch-card machine that processed punch cards for the 1890 census, leading to the Hollerith Integrating Tabulator. Note that these tabulators generated output on counter dials (below); they didn't print any output, tabular or otherwise.
Hollerith Electric Tabulating System (replica). Cards were manually fed into the reader on the right, and results were counted on the dials.
The second type of tabulator was the tabulating typewriter (1890). These devices were simply typewriters with tab stops to make it easier to produce tables. (The "tabulating key" on these typewriters is is the root of the "tab" key on the modern computer keyboard.) The decimal tabulator (1896) added multiple tab keys that would tab to the proper location for a 1-digit number, 2-digit number, 3-digit number, etc.
Underwood 6 typewriter with decimal tabulator (1934). Inset shows the decimal tab keys enlarged: "Tab Stop Clear", ".", "1", "10", "100", "1000", "Tab Stop Set". Interestingly, the platen scale shows 132 tick marks. Photo courtesy of J Makoto Smith.
A major part of my analysis is that the standard form hole-to-hole width is typically divisible by 5/32" (although not always). I couldn't find a stated reason for this, but I have a theory. To support continuous forms, pin wheel assemblies (below) are attached to the ends of the platen cylinder. Consequently, the hole-to-hole distance is determined by the platen width. It makes sense for the platen width to be a multiple of 5/32" so characters fit exactly. The distance from the edge of the platen to the pin centers appears to be 5/32". (I measured pixels in photos to determine this; I don't have solid proof.) Thus, the hole-to-hole distance will also be a multiple of 5/32"
The pin-feed platen consists of two pin wheels that go on the end of the platen cylinder. Adapted from IBM Operators Reference Guide (1959) page 80.
The IBM 285 tabulator was configured with 3 to 7 print banks, each 1 7/8" wide. (See Machine Methods of Accounting: Electric Tabulating Machines page 14.) I believe these were the source of the standard form widths 8", 9 7/8", 11 3/4", 13 5/8" and 15 1/2" (after adding some margin). Many of the other standard sizes are nice round numbers (e.g. 11" and 16"). 18 15/16" was probably selected to yield 18" paper (Arch B) with the punched margins (actually 1/16" smaller than 18" so the hole-to-hole width is a multiple of 5/32"). I can't come up with any plausible explanation for 17 25/32", but it may be related somehow to 17" ledger paper (ANSI B) or perhaps untrimmed paper sizes (SRA2, Demy).
The diagram below gives some information on the dimensions of forms for the IBM 407 accounting machine.
IBM's recommended specifications for forms. From Reference Manual, IBM 407 Accounting Machine.