WHO INVENTED THE CALCULATOR?

The first calculators were abaci, and were often constructed as a wooden frame with beads sliding on wires. Abacuses were used centuries before the adoption of the written Arabic numerals system and are still used by some merchants, fishermen and clerks in China and elsewhere.
William Oughtred invented the slide rule in 1622

In 1822 Charles Babbage proposed a mechanical calculator, called a difference engine.

HOWEVER, French Blaise Pascal invented the calculator. He did this to help his dad who was a tax adjuster. Then Gottfried Leibnitz improved on Pascal idea with a machine that would add, subtract, multiply, and divide.

John Napierin invented the movable multiplication table engraved on a series of square section metal rods, called Napiers Bones.

We tend to take a cheap hand held calculator for granted. They're easy to use and it's hard to imagine life with out them. But not very long ago a hand held calculator was very expensive and very different from the ones we use today.