Introduction: The history of computers is a big story, but I want to focus on the impact of users on the shape of the technology. The early history of computers shows the significance of demand.

• Babbage (born in 1791) built a mechanical calculator that was only slightly faster than a person
• he conceived of a mechanical general purpose computer, which he called an analytical engine , but it could not be built because the parts could not be machined to close enough tolerances.
• the analytical engine was to be programmed with wooden plates with holes punched in them, which Babbage copied from the system used to control the weaving of complex patterns on a Jacquard loom
• a friend of his, Augusta Ada Byron, Countess of Lovelace and daughter of the poet Lord Byron, wrote an account of Babbage's work and analyzed how to program the machine.

• I would start the history of computers with the computers used by astronomers in the late 19th century

women computers at Harvard College Observatory c. 1890

• These women usually had a high school education, although some of them had studied astronomy in college.  They did the lengthy calculations necessary for such enterprises as computing the orbits of comets from a series of observations, using 10 place tables of logarithms.  They also measured and cataloged the stars on photographic plates, and some of them made important contributions to astronomy as scientists in their own right.
• women computers were used in other fields, particularly electrical and aeronautical engineering
  

• The typewriter because commercially viable in the 1870s--one of the first innovations of the American System of Manufacturing.  Along with the typewriter came carbon paper and then mimeograph paper--part of the value of the typewriter was for making multiple copies, a kind of data handling.

• Companies that made profits with typewriters looked for similar opportunities.  People had been inventing calculating machines for years, but the trick was moving the idea to mass production and mass use.  The principle of the typewriter keyboard was the biggest help, making machines much more useable by the 1880s.
• big businesses were finding that accounting was a bottleneck, and adding and calculating machines not only made accounting more accurate but made it practical to produce more information (such as trial balances).
• Larger stores in the 1880s, like the new department stores, wanted control over clerks, and so were very interested in the new cash register.

• The most sophisticated machines were developed to tabulate the U.S. census, eg. a machine developed by Herman Hollerith that could read punched cards and perform simple arithmetic
• one of the firms that got its start building machines for the census was the Tabulating Machine Company, founded about 1890, which eventually became IBM

Pickett 10" Powerlog Exponential slide rule

    How to use a slide rule and one to try

• The differential analyzer was an amazing electronic analog device developed for electrical engineering calculations, most notably by Vannevar Bush.

• Worked like a slide rule and could solve differential equations with one variable.  It was a mechanical, electrically powered device in which numbers were represented by directly measurable quantities so you computed by manually measuring the number of degrees specific gears rotated.
• the rooms full of women acquired various kinds of mechanical adding machines, some of which could even multiply.  Rooms full of women were used even to make aerodynamics calculations
• IBM even developed a mechanical machine called the AUtomatic Sequence Controlled Calculator, controlled by paper tape

• Large numbers of women with science degrees were hired to do ballistic computation, but they couldn't keep up with the demand
• Bell Labs and Harvard developed electromechanical machines using telephone relays.
• The Bell Labs Complex Computer was completed in 1939 and performed useful work until 1949. It was 50 feet long, eight feet tall, three feet deep, and had 765,299 separate parts connected by 530 miles of wire and 1,444 dials.

  Harvard Mark I

• At Harvard Harold H. Aitken , with engineers from IBM and Grace Hopper (quotes ), built the Automatic Sequence Controlled Calculator or Mark 1 --three to five times faster than a skilled person with a mechanical calculator.  Weighed 5 tons, was 50 feet long and eight feet high, and had 500 miles of wire.  Each multiplication took six seconds, and division twice as long. A second version in Nov. 1944 even had an internal memory for 100 ten digit numbers.  IBM was very miffed not to be given credit and started their own computer research.
  
• the demand for an all-electronic (and therefore faster) computer was clear, and that leads to ENIAC, where we will start next class