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History of Calculators
If we define a calculator as a device that aids mathematical computation then the oldest calculator is certainly the human hand. Another calculator that has served mankind for thousands of years is the abacus. The oldest surviving abacus was used in 300 B.C. by the Babylonians. The abacus is still in use today, principally in the far east. A skilled abacus operator can work on addition and subtraction problems at the speed of a person equipped with an electronic hand calculator (multiplication and division are slower). Just like a hand, an abacus doesn't actually perform computations, instead its value is that it aids the memory of the human performing the calculation. While a modern abacus consists of rings that slide over rods, the older one pictured below dates from the time when pebbles were used for counting (the word "calculus" comes from the Latin word for pebble).
Although Leonardo da Vinci made drawings of gear-driven computing machines, he apparently never built any.
The first gear-driven calculating machine to actually be built was probably the calculating clock, so named by its inventor, the German professor Wilhelm Schickard, in 1623. This device got little publicity because Schickard died soon afterward in the bubonic plague.
The first mechanical calculator to be mass produced and offered for sale was the Pascaline, invented in 1642 by Blaise Pascal who, at age 19, wanted to ease the workload of his father who was a tax collector. Pascal built 50 of this gear-driven, one-function calculator (it could only add) but couldn't sell many because of their exorbitant cost.
Shown below is a 6 digit model for those who couldn't afford the 8 digit model. This Pascaline is opened up so you can observe the gears and cylinders which rotate to display the numerical result. Up until the present age when car dashboards went digital, the odometer portion of a car's speedometer used the very same mechanism as the Pascaline to increment the next wheel after each full revolution of the prior wheel.
Mechanical calculators continued to improve. If you worked as a bookkeeper in the early 1900's you probably used a Comptometer like the one shown below. Note that this device does not have a power cord.
Electronic computers began to supplant mechanical computers starting with the famous ENIAC which was built during World War II to compute the trajectories of shells fired from large guns such as those on battleships. Don't hunt for ENIAC in the following picture, as all of what you see (and more) is ENIAC.
You've no doubt heard of the micro-electronics revolution where semiconductor technology allowed electronic devices as large as ENIAC to be shrunk down to a few millimeters. Computers that had been as large as rooms started to appear on desktops and eventually in shirt pockets.
The Japanese companies Sharp, Canon, and Sanyo all began selling hand-held, four-function electronic calculators in 1971.
In January of 1972 Hewlett-Packard introduced the HP-35, the first scientific handheld calculator that included transcendental functions like natural logarithm, sine, and cosine. It's initial list price was $395 and by 1973 slide rule manufacturers were declaring bankruptcy. The NASA engineers who managed to put a man on the moon in 1969 were still employing slide rules for much of their work.
Hewlett-Packard had previously sold desktop-sized calculators when Bill Hewlett decided that it was now feasible to manufacture a shirt-pocket sized unit. After Bill ordered his company to design such a unit his engineers showed up in his office to measure his shirt pocket to make sure they would get it right. Even though analysts had predicted the unit wouldn't sell, HP sold a hundred million in just the first year. Hand calculators were the "home computers" of the 1970s.
While ground-breaking, the HP35 wasn't programmable. In 1974 HP introduced the HP-65 which was the first ever programmable handheld calculator. This Windows program resembles another HP programmable calculator, the HP-29C, introduced in 1977 at a list price of $195.
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