It could probably be argued I know how to code. I am not sure what stops me from working on the ideas that constantly come into my head. Probably that I have things I enjoy doing even more and at this point still enjoy learning stuff more than I enjoy doing stuff for code.
Choice link
https://sgimenez.github.io/laby/
I reckon it depends what sort of coding.
Anybody can drill a hole in a bit of wood, it is not completely trivial but you can get the necessary stuff fairly quickly. Not everybody knows enough to be a precision machinist though.
By similar token yeah I reckon the amount of people that could truly get to grips with assembly and high performance/secure/crazy mathematical C family stuff is somewhat less than the total population. Hopefully we can avoid getting caught in the Turing complete trap but a number rather more close to said total could probably get some basic operations of their choosing done on numbers (think spreadsheets), fiddle with wildcards and regex, handle some if else stuff and generally do something useful (quicker or more accurate than hand sorting and still done within a timeframe most humans can live with) with current gear, doubly so if a kind of more simplified or complete API set was available (I imagine you and I would hate it and find it limiting but it is what it is).
http://portableapps.com/
http://codeblocks.codecutter.org/
https://www.virtualbox.org/ (a portable version also exists)
Any number of livecds exist.
Get it on a USB drive, do it right and none of it will touch the system in question and be as functional as anything you have of your own. Unless you meant your time is limited on it, in which case if you have a phone or tablet there are quite a few things you could be doing on one of those.