A 10 key adding machine evolved from a mechanical machine that added numbers to electrical devices that accomplished the same task plus other mathematical calculations. Some machines include a printing capability. The arrangement of numbers on a computer keyboard has its roots in the early machines.
The first 10-key machine with the present-day layout was first manufactured by Sundstrand Adding Machine Company in 1914. In 1923, the first direct subtracting model was introduced. Keys that control mathematical functions were arranged along both sides of the number keys.
The modern machine that uses rows of 7,8,9 and 4,5,6 and 1,2,3 plus a zero key, proved to be a time-saver and simpler to use. People learn this arrangement easily and input numbers without looking, or by touch. When typing or adding a string of numbers, the 10 key pad is more efficient and accurate than using the numbers situated across the top of a traditional keyboard.
The 10 key layout, first introduced in the early 20th century has endured into the 21st century. Now, people add numbers on electric machines, hand-held calculators, computer keyboards, and on the touch screens of phones. The basic concept of touch typing to enter numbers, has remained the same since the mechanical predecessors.