Thoughts on the word “counterpart”

So, since I’ve seen a number of Tron fics use “counterpart” for a program’s romantic partner…

…I’ve started to notice a thing in my own programming software.


BBEdit file menu, showing the option "Open Counterpart" ALT


Now, I don’t understand what this means, because I don’t actually write programs. I use BBEdit for making html pages for my website (and also AO3 fics, because they need to be formatted like html pages).


And all I can find in the BBEdit support is this stuff in the release notes for version 9.6:


"Open Counterpart" can now be used for files which will be implictly created at save; for example, bbedit foo.h followed by an Open Counterpart command will open foo.cp if it can be found using the standard rules.ALT
"Open Counterpart" will ask Xcode for the file's counterparts when possible.ALT


…so, from that, I would guess that a program’s “counterparts” are other programs that are somehow vitally involved in its functioning.


…And that a program can have more than one of them.


Tron and Ram and Yori posed together (composite created by pasting together a few different black and white promo photos)ALT



… Others with more coding knowledge, please contribute more context if possible?