Extract from The PC Pioneers
It was today in 1979 that VisiCalc (Visible Calculator) the first computer spreadsheet arrived – I can’t begin to tot up the days that I have spent on it and its successors since!
But sadly the originators Dan Bricklin and Bob Frankston were unable to get the notion patented,
The advice the US Patent Office gave to the VisiCalc team at the time was that they had a less than 10% chance of getting a patent awarded for software. Given the high costs involved and the poor chances of a positive outcome they proceeded relying instead on copyright and trademarking.