Alan Kay was quoted several years ago to the effect that there had been only three new things in software in the preceding 20 years (effectively the lifespan of PCs). One of them was Spreadsheets.
Does anyone remember the other two?
Who is Alan Kay? (a few may ask.) His work at Xerox Parc arguably did more to shape our current software paradigm than any other influence.
I will try to remember what I said, but none of the answers so far are correct (every one of them was done in the 60s and 70s before the commercialization of PCs in the 80s).
However, we could start all over and try to think of new inventions in computing since the 1980s.