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In 1978, a Harvard Business School student named Dan Bricklin was sitting in a classroom, watching his accounting lecturer filling in rows and columns on the blackboard.
Every time the lecturer changed a figure, he had to work down and across the grid on the board, erasing and rewriting other numbers to make everything add up, just as accounting clerks all over the world did every day in the pages of their ledgers.
Work - Spread - Fold - Ledger - Spreadsheet
It's boring and repetitive work. A two-page spread across the open fold of the ledger is called a "spreadsheet".
The output of several paper spreadsheets provides the input for larger, master spreadsheets.
Data - Chain - Hours - Work - Pencil
Changing any of the data in that chain might mean hours of work with a pencil, rubber, and a calculator.
Like many business school students, Mr Bricklin had had a real job before going to Harvard - he'd worked as a programmer at Wang and DEC, two big players in 1970s computing.
Earth - Anyone - Blackboard - Paper - Ledger
Why on Earth would anyone do this on a blackboard or paper ledger, he wondered, when you could do it on a computer instead?
50 Things That Made the Modern Economy highlights the inventions, ideas and innovations that helped create the economic world.
BBC - World - Service - Episodes - Programme
It is broadcast on the BBC World Service. You can listen to all the episodes online or subscribe to the programme podcast.
So he wrote a program for the new Apple II personal computer: an electronic spreadsheet.
Friend - Bob - Frankston - Software - October
His friend Bob Frankston helped him sharpen up the software - and, on 17 October 1979, VisiCalc went on sale.
Almost overnight, it was a sensation.
Accounting - Programs - VisiCalc - Spreadsheet - Interface
Other financial and accounting programs had long existed but VisiCalc was the first with the modern spreadsheet interface.
It is widely thought to be the first "killer app", a software program so essential that you'd buy a computer just to be able to use it.
Mr - Bricklin - Notes
As Mr Bricklin notes on his...
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