The first computers were people who performed complex calculations manually. Early mechanical aids for calculations included the abacus and inventions by Napier, Pascal, and Leibniz that used gears to perform addition, subtraction, multiplication and division. Herman Hollerith developed the first electromechanical tabulating machine using punched cards to automate census data processing, laying the foundation for IBM. During WWII, the military funded development of programmable digital computers like the Harvard Mark I to compute artillery firing tables, establishing computers for scientific and government use.

1. HISTORY OF COMPUTERS

5. A typical computer operation back when computers were people.

8. the oldest surviving abacus was used in 300 B.C. by the Babylonians

9. A more modern abacus. Note how the abacus is really just a representation of the human fingers : the 5 lower rings on each rod represent the 5 fingers and the 2 upper rings represent the 2 hands. The abacus is still in use today, principally in the far east. A modern abacus consists of rings that slide over rods,

11. An original set of Napier's Bones [photo courtesy IBM]

12. A more modern set of Napier's Bones

13. Napier's invention led directly to the slide rule , first built in England in 1632 and still in use in the 1960's by the NASA engineers of the Mercury, Gemini, and Apollo programs which landed men on the moon.

14. Leonardo da Vinci (1452-1519) made drawings of gear-driven calculating machines but apparently never built any . A Leonardo da Vinci drawing showing gears arranged for computing

15. 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. Schickard's Calculating Clock

33. An operator working at a Hollerith Desk like the one below

34. Preparation of punched cards for the U.S. census

35. A few Hollerith desks still exist today [photo courtesy The Computer Museum]

42. You can see the 50 ft rotating shaft in the bottom of the prior photo. This shaft was a central power source for the entire machine. This design feature was reminiscent of the days when waterpower was used to run a machine shop and each lathe or other tool was driven by a belt connected to a single overhead shaft which was turned by an outside waterwheel. A central shaft driven by an outside waterwheel and connected to each machine by overhead belts was the customary power source for all the machines in a factory

43. Here's a close-up of one of the Mark I's four paper tape readers. A paper tape was an improvement over a box of punched cards as anyone who has ever dropped -- and thus shuffled -- his "stack" knows. One of the four paper tape readers on the Harvard Mark I (you can observe the punched paper roll emerging from the bottom)

45. The first computer bug [photo © 2002 IEEE]