Antikythera Mechanism

n 1900, a Greek sponge diver spotted a shipwreck off the coast of the tiny island of Antikythera. Little did he know that amongst the jewelry and statues recovered from the wreck, the most precious item would be a lump of green rock with gears sticking out of it

the "rock" turned out to be the earliest example of analog computer: an intricate mechanism with more than 30 gears and writings that scientists thought was used to calculate the motion of the sun and the moon against a background of fixed stars.

Wilhelm Schickard’s Calculating Clock

In 1623, Wilhelm Schickard of the University of Tübingen, Württemberg (now part of Germany), invented the first mechanical calculator. Schickard’s contemporaries called the machine the Speeding Clock or the Calculating Clock.
Schickard’s calculator, which was built 20 years before Blaise Pascal and Gottfried Leibniz’s machines, could add and subtract six-digit numbers (with a bell as an overflow alarm!). This invention was used by his friend, astronomer Johannes Kepler, to calculate astronomical tables, which was a big leap for astronomy at the time. For this, Wilhelm Schickard was considered by some to be the "Father of Computer Age."