### Post by Chicago Astronomer Joe on Jul 6, 2005 1:36:33 GMT -6

**When computers were human...**

In the not-so-distant past, engineers, scientists and mathematicians routinely consulted tables of numbers for the answers to questions that they could not solve analytically. Sin(.4)? No problem: look it up in the Sine table. These tables were prepared by teams of people called computers (no, really -- that's where the term comes from) who typically had only rudimentary math skills. The computers were overseen by more knowledgeable mathematicians, who designed the algorithms and supervised their work." Read below for Stern's review of David Alan Grier's book When Computers Were Human.

The most important of these teams was the Mathematical Tables Project, organized by the Work Projects Administration in the United States during the Great Depression. WPA rules required the hiring of people with virtually no skills, so much of the definitive work of the Mathematical Tables Project was computed by people who had mastered only addition. They were not authorized to subtract, let alone delve into the mysteries of multiplication or division. The algorithmic steps assigned to them sometimes produced negative numbers, and it goes almost without saying that these computers had no idea what these were or how to handle them. Gertrude Blanch, the mathematician who oversaw their work, had devised a scheme whereby positive numbers would be written in black, negative numbers in red. On the wall in front of her human computers hung a poster that encapsulates much of the era of human computing. It read:

Black plus black is black

Red plus red is red

Black plus red or red plus black, hand the sheets to team 2

Entire story here: books.slashdot.org/article.pl?sid=05/07/05/1622241

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I never used a slide rule, but I find the instrument facinating. I want one!