I just read an interesting story on Wired.com about how the Graphing Calculator made it into the Mac OS (still in Classic).
The software author's version (referenced in the article) is here.
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Avitzur sneaked into Apple's California HQ for six months to write a software program that, through luck and hard work, is still included on every Mac sold today.
Unemployed and living on savings, Avitzur worked 12-hour days, seven days a week, to create Graphing Calculator in the unlikely hope that Apple would bundle it with new computers.
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The software author's version (referenced in the article) is here.