An adding machine is a type of calculator. Usually this sort of calculator is specialized for bookkeeping calculations.

In the United States, very old adding machines were usually (always?) built to read in dollars and cents. They required the user to pull a crank to add numbers. The numbers were input by pressing keys on a large keypad: for instance, the amount $30.72 was input using keys corresponding to "$30", "70¢", and "2¢", and then pulling the crank. Subtraction was impossible, except by adding the complement of a number (for instance, subtract $2.50 by adding $9,997.50).

A later adding machine, called the Comptometer, did not require that a crank be pulled to add. Numbers were input simply by pressing keys. The machine was thus driven by finger power.

Some adding machines were electromechanical -- an old-style mechanism, but driven by electric power.

Some "ten-key" machines had input of numbers as on a modern calculator -- 30.72 was input as "3", "0", "7", "2". These machines could subtract as well as add. Some could multiply and divide, although including these operations made the machine more complex.

These old machines could be difficult to maintain and might give wrong answers if the mechanism failed. It was probably better to learn to use an abacus.

Modern adding machines are like simple calculators. They often have a different input system, though.

Note: Sometimes the adding machine will have a key labeled * instead of T. In this case, substitute * for T in the examples above. Alternatively, the plus key may continuously total instead of either a * or T key. Sometimes, the plus key is even labeled thus: +/=

William Seward Burroughs received a patent for his adding machine on August 21, 1888. The Burroughs Adding Machine Company evolved to produce electronic billing machines and mainframes, and eventually merged with Sperry to form Unisys. The grandson of the inventor of the adding machine is Beat author William S. Burroughs (best known for Naked Lunch.)

The Adding Machine is also a 1923 expressionist play by the American playwright Elmer Rice. The play dramatizes

...the dreary life, death, and after-life of Mr. Zero, a white-collar drone who learns that, after twenty-five years, `the Boss' has fired him in favor of a machine. In the expressionistic spectacle depicting Zero's inner turmoil, the stage rotates, and overlapping sound effects screech as the one-dimensional Boss jabbers, `efficiency! economy! business! business! BUSINESS'. Tried and executed for the boss's murder.... Zero retreats to a dingy supernatural office, where he operates a celestial adding machine. Finally, `Lieutenant Charles' announces his plans to reincarnate him in order to operate `a super-hyper-adding machine, as far from this piece of junk as you are from God'.... Rice's stage directions call for a stream of adding machine tape that `climbs the walls and chokes the doorways.' In production, designer Lee Simonson had the inspiration to fill the stage with an immense adding machine... The increased visual importance of the adding machine in this final scene helps to make up for its largely tangential relationship to the rest of the play and reinforces its root message about the indifference of modern society towards the debased souls that it produces. (Dennis G. Jerz, Technology in American Drama, pg. 22, 28)