Copy and paste is a design error.
Once a developer groks this quote, he/she has already achieved another level of understanding software development.
Yes, this is a cop-out. My body just feels so blah the entire day after eating high quality spaghetti doused in substitute spaghetti sauce (tomato powder + spices + TVP, the cheap sauce used in street food) so I don’t feel like writing. I personally don’t mind eating street-food level spaghetti (because otherwise it would be hypocritical for me) but serving it in the dinner table in the guise of “normal” spaghetti is just plain wrong.
Anyway, back to the quote. Explaining the quote here would defeat the purpose of making the post as short as possible. So if you want to know what I mean about that quote, either wait for me to write about “refactoring”, or do your homework.
I will, however, point out that I could not find the source of the quote above. Sure, David Parnas is a pioneer in modular design, but most of his papers predate the copy-paste feature of the Mac. The only place I could find where he is attributed to saying something against copy and paste programming is in one of Steve McConnell’s articles. So technically, the quote should be:
David Parnas says that if you use copy and paste while you’re coding, you’re probably committing a design error.