 1623
 Wilhelm Schickard (15921635), of Tübingen, Württemberg (now in
Germany), makes his "Calculating Clock". This is a 6digit
machine that can add and subtract, and perhaps includes an overflow
indicator bell. Mounted on the machine is a set of Napier's Rods, a
memory aid facilitating multiplications. The machine and plans are lost
and forgotten in the war that is going on. (The plans were rediscovered
in 1935, lost again in the war, and rerediscovered by the same man in 1956!
The machine was reconstructed in 1960 and found to be workable.)
Schickard was a friend of the astronomer Kepler.
 16445
 Blaise Pascal (16231662), of Paris, makes his "Pascaline". This
5digit machine can only add, and that probably not as reliably as
Schickard's, but at least it doesn't get forgotten  it establishes the
computing machine concept in the intellectual community. (Pascal sold about
1015 of the machines, some supporting as many as 8 digits, and a number of
pirated copies were also sold. No patents...)
This is the same Pascal who invented the bus.
 1674
 Gottfriend Wilhelm von Leibniz (16461716), of Leipzig, makes his
"Stepped Reckoner". This uses a movable carriage so that it can
multiply, with operands of up to 5 and 12 digits and a product of up to 16.
But its carry mechanism requires user intervention and doesn't really work
in all cases anyway. The calculator is powered by a crank.
This is the same Leibniz or Leibnitz who coinvented calculus.
 1775
 Charles, the third Earl Stanhope, of England, makes a successful
multiplying calculator similar to Leibniz's.
 17706
 Mathieus Hahn, somewhere in what is now Germany, also makes a
successful multiplying calculator.
 1786
 J. H. Müller, of the Hessian army, conceives the idea of what came
to be called a "difference engine". That's a specialpurpose calculator for tabulating values of a polynomial, given the differences between
certain values so that the polynomial is uniquely specified; it's useful
for any function that can be approximated by a polynomial over suitable intervals. Müller's attempt to raise funds fails and the project is forgotten.
