The comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr Felt in 1887. It was a key-driven calculator that was …

May 23, 2025 · The comptometer was the first commercially successful key-driven mechanical calculator. It was invented in 1862.

The Comptometer was the first successful key driven adding and calculating machine. "Key driven" means that just pressing the keys adds the numbers entered to the total - no other …

The Comptometer was the first push button calculator and also the first calculator to achieve commercial success. It could perform addition, subtraction, multiplication and division.

A Comptometer is a mechanical (or electro-mechanical) adding machine. It was the first adding device to be operated solely by the action of pressing keys arranged vertically and …

A visual explanation of how the Comptometer, the first practical key-driven calculator, works. Comptometers were manufactured continuously from 1887 until the 1970s.

In 1887 American inventor Dorr E. Felt introduced the Comptometer, a non-printing key-driven calculating machine whose chief advantages were speed, versatility, and ease of use.

Mar 26, 2024 · The comptometer was the first commercially successful key-driven mechanical calculator and a revolutionary device that transformed bookkeeping, accounting and many …

Comptometer training schools were established in 1905 to formalize operator training, and to teach new methods of calculation. Comptometer schools typically recruited young women, and …

These instructions for performing the basic 4-functions on a "Comptometer" type calculator are taken from the operating instructions of the Sumlock machine manufactured by the Bell Punch …