The Comptometer (1887)

The comptometer was the first commercially successful key-driven mechanical calculator, patented in the USA by Dorr E. Felt in 1887. A key-driven calculator is extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed and a skilled operator can enter all of the digits of a number simultaneously, using as many fingers as required, making them sometimes faster to use than electronic calculators. Consequently, in specialized applications, comptometers remained in use in limited numbers into the early 1990s, but with the exception of museum pieces, they have all now been superseded by electronic calculators and computers.

Manufactured without interruption from 1887 to the mid-1970s, it was constantly improved. The mechanical versions were made faster and more reliable, then a line of electro-mechanical models was added in the 1930s. Notably, it was the first mechanical calculator to receive an all-electronic calculator engine in 1961, with the ANITA Mark VII model released by Sumlock Comptometer. This created the link between the mechanical calculator industries and the electronic.

Although the comptometer was primarily an adding machine, it could also do subtractions, multiplication and division. Its keyboard consisted of eight or more columns of nine keys each. Special comptometers with varying key arrays were produced for a variety of special purposes, including calculating currency exchanges, times and Imperial weights. The name comptometer was formerly in wide use as a generic name for this class of calculating machine.

The First Comptometers

The desktop computer became common for accountants in the mid-1980's. It took a few more years for it to become common in business.

The computer is a natural for double entry bookkeeping. The procedures are just as they have been for many years. Journals, ledgers, spread sheets, and financial statements. Now, they are always in balance. Spelling, printing, and statements are correct. Beautiful! The benefits did not come all at once. My first desk-top computer required that I take it apart and set dip switches. I followed the instructions and didn't have any problem.

If you wanted more memory or more speed you could pay more and the increase would appear. Early software could be a challenge. Once you figured out the bugs you tried not download updates. Come to think of it some software is still that way.

Click here to learn how to operate the Comptometer

"Comptometers were used full time by 4 to 6 operations in the cost department at “Quaker Maid”. When I worked there in the late 1960’s, Quaker Maid was the food manufacturer division of A&P. Operating the comptometer was just not indexing the number. Only the five first numbers were used. Adding 8 to the total was achieved by indexing number 5 and then number 3. It required total concentration. The operators were very fast and very accurate. No print out. No adding machine tape. WOW! The comptometer was dificult to learn and even more dificult to operate. You need total concentration, nimble fingers, and the abilit to calculate in your head on the fly. Luckily, I had a Rotary Calculator." - Gerald Dix