The oldest known calculating device is the abacus, which is believed to have been invented and in use in Babylonia (now Iraq) about 5,000 years ago. The abacus was used in China as well and was used to count and provide a reliable way to calculate additions and subtractions.
Scottish mathematician John Napier (born around 1550) invented a calculating device called "Napier's Bones." It was made of rods (often bones) with squares inscribed on them. The device allowed the user to calculate multiplications. Napier also invented logarithms, which were further developed by the mathematician Henry Briggs. Edmund Gunther (1581-1626) and William Oughtred (1574-1660) went on to invent and develop the slide rule based on their concepts.
In 1623, German astronomer Wilhelm Schickard (1592-1635) developed what he called the "calculating clock," a machine that was capable of calculating addition, subtraction, division and multiplication functions. He did not present the invention publicly, however, and it was destroyed by a fire in 1624.
The first calculating machine that was introduced to the public was invented by French mathematician/writer/philosopher Blaise Pascal (1623-1662) in 1642. The 19-year-old Pascal was driven to invent the mechanism to aid in the endless calculations he did for his father's business. His invention, called the Pascaline, was the first to automatically carry the digits from one column to the next. His prototype could handle five-figure numbers, and subsequent versions could handle up to eight figures.