Answer Geek: Calculator vs. Phone Layouts

Q U E S T I O N: Why do the numeric keypads on computers and calculators reverse the configuration on a telephone? I’m certain that thousands of wrong numbers are dialed daily because of this. — David K.

Q U E S T I O N: Why do the numbers on telephones go from 1 in the top left corner to 9 in the bottom right, while calculators and computer number pads go from 1 in the bottom left corner to 9 in the top right corner? — Joel K.

A N S W E R: A wonderful question, gentlemen, and something that I have puzzled over myself. After all, here are three devices that we use on a daily basis, and they all share a basic layout — an array of 10 numbers in a three-by-three arrangement with the zero sitting down below. Yet the numbers are reversed. So what gives? Why aren’t all such devices created equal, anyway?

Let’s first set the context. The time is the late 1950s. The place, Bell Laboratories, where researchers are preparing to introduce an alternative to the rotary telephone, something they called push-button dialing (which later came to be marketed as “Touch Tone” dialing). The question: how to arrange the numbers.

There were two logical models, of course. The existing rotary phone with its circular dial and counterclockwise number arrangement, with the 1 sitting in the upper right, was one. The calculator was the other. Back then, the industry-standard typical calculator had nine columns of numbers, with 10 numbers in a column, the lowest digits at the bottom, starting with 0 and moving up to 9, and was basically a mechanical adding machine that closely resembled a cash register.

One common explanation for the discrepancy between the phone and the calculator is that phone company engineers intentionally reversed the calculator layout because their research showed that people who were already adept at using a calculator punched the buttons too quickly for the telephone switching equipment to correctly register the numbers. But accounts from people who worked for Bell Labs at the time indicate that this version isn’t necessarily the case.

A Case Study

The real answer seems to lie in a study conducted at Bell Labs titled “Human Factor Engineering Studies of the Design and Use of Pushbutton Telephone Sets.” Published in the July 1960 issue of the Bell System Technical Journal, the report says that researchers tested a number different layouts including the three-by-three matrix with the zero at the bottom; versions with two rows of five numbers, arrayed either horizontally or vertically; and circular configurations with numbers laid out in clockwise and counterclockwise fashion. The study concluded that the three-by-three version with 1-2-3 in the top row was the easiest for people to master.

There was another reason as well. When it came time to match letters of the alphabet up with the numbers, putting 1-2-3 across the top made a lot more sense because it was the most natural way to get ABC in the top row. If 7-8-9 had been at the top, one of two things would have happened — the letters and the numbers would have run in opposite directions, or PRS would have been the first set of letters. Either arrangement would have seemed very odd, indeed.

All this raises another interesting question. When Bell Labs began exploring keypad layouts in the late 1950s they contacted all of the leading calculator manufacturers to find out why they had chosen to put low numbers at the bottom and high numbers at the top rather than the other way around. The answer, apparently, was a big shrug. It turns out that decision was largely arbitrary: no one had done any research about which layout was most convenient for users. Still, when it came time to place a numeric keypad on a computer keyboard, the calculator model with 7-8-9 at the top prevailed.

Todd Campbell is a writer and Internet consultant living in Seattle. The Answer Geek appears weekly, usually on Thursdays.

Join the Discussion
blog comments powered by Disqus
You Might Also Like...