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**An Illustrated History of Computers**

John Kopplin © 2002

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

Counting Tables

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**A Modern Day Abacus (Oldest surviving, 300 B.C)**

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.

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Napier's Bones In 1617 John Napier invented logarithms, which are a technology that allows multiplication to be performed via addition.

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**Schickard's Calculating Clock**

The first gear-driven calculating machine to actually be built in 1623.

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A Pascaline In 1642 Blaise Pascal, at age 19, invented the Pascaline a gear-driven one-function calculator (it could only add).

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**Descendents of these punched cards have been in use ever since.**

Power Loom In 1801, Joseph Marie Jacquard invented a power loom that could base its weave upon a pattern automatically read from punched wooden cards. Descendents of these punched cards have been in use ever since.

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Analytic Engine Charles Babbage created plans to build the Analytic Engine when he realized that punched paper could be employed as a storage mechanism. Because of the connection to the Jacquard loom, the two main parts of his Analytic Engine were called the "Store" and the "Mill." The Store was where numbers were held and the Mill was where they were "woven" into new results. In a modern computer these same parts are called the memory unit (store) and the central processing unit (mill). The Analytic Engine also had a key function that distinguishes computers from calculators: the conditional statement. A conditional statement allows a program to achieve different results each time it is run. Unfortunately, funding was not available and the Analytic Engine was never built.

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Hollerith Desk In the late 1880’s Herman Hollerith, proposed Jacquard's punched card design for the purpose of computation for the US Census and it was accepted. Hollerith's invention, known as the Hollerith desk, consisted of a card reader which sensed the holes in the cards, a gear driven mechanism which could count (using Pascal's mechanism which we still see in car odometers), and a large wall of dial indicators (a car speedometer is a dial indicator) to display the results of the count.

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Hollerith Desk (cont.) The patterns on Jacquard's cards were determined when a tapestry was designed and then were not changed. Today, we would call this a read-only form of information storage. Hollerith had the insight to convert punched cards to what is today called a read/write technology. Hollerith's technique was successful and the 1890 census was completed in only 3 years at a savings of 5 million dollars. Hollerith built a company, the Tabulating Machine Company which, after a few buyouts, eventually became International Business Machines, known today as IBM.

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Mark I Built as a partnership between Harvard and IBM in The first programmable digital computer made in the U.S. Constructed out of switches, relays, rotating shafts, and clutches. Weighed 5 tons, incorporated 500 miles of wire, was 8 feet tall and 51 feet long, and had a 50 ft rotating shaft running its length, turned by a 5 horsepower electric motor. To appreciate the scale of this machine note the four typewriters in the foreground of the following photo.

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**The First Computer “Bug"**

Grace Hopper. Hopper found the first computer "bug": a dead moth that had gotten into the Mark I and whose wings were blocking the reading of the holes in the paper tape. The word "bug" had been used to describe a defect since at least 1889 but Hopper is credited with coining the word "debugging" to describe the work to eliminate program faults.

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IBM Stretch The computer of 1959: the picture on the left is just that of the operator's console, the picture on the right show the rest of its 33 foot length:)

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**Mini-computers Computer of 1969**

(Called a “mini” but still rather large in size compared to what we see today.)

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Apple I A home computer of 1976 such as this Apple I which sold for only $600

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IBM Personal Computer By the 1990's a university student would typically own his own computer and have exclusive use of it in his dorm room.

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**Microelectronics Revolution**

This allowed the amount of hand-crafted wiring seen in the photo to the left to be mass-produced as an integrated circuit which is a small sliver of silicon the size of your thumbnail shown I the photo to the right.

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Today’s Computers

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