Linux/Unix & their associated command line stuff. The number of times it's come in handy to be able to SSH into a machine that's way over there and do stuff is immense. Sadly I waited till Uni to learn, and I wonder where I'd be now if I'd internalised these concepts by the age of 15.
Need to log something you've just done? Redirect the output into a file. Boom. No longer do you have to find the bit of software that does everything, you just need programs that do simple stuff you can repurpose*.
Reading FOLDOC a bit to get the history was handy too. Thinking of computers as CPUs attached to teletypewriters, with all that fancy graphics stuff as optional explains a lot of how current software ended up the way it is.
*Totally not advocating mainstream computing for every user end up like this, btw. (Linux still makes me cry on a regular basis) Just that being able to drop to a command line and chain together commands or write scripts is so powerful that it's a game changer.
Majorly with you on this one. Piping in shell changed my life, and then piping in R (via Magrittr via dplyr) changed my life again.
This is the question asked by John Cook on Twitter. He lists responses from different people:
Mine are: quantum mechanics, Python, cooking, the language of philosophy.
What learning curve do you wish you'd climbed sooner? Give reasons and stories if you feel like it. Do you think other people should climb the same curves?