It was literally the unit with implementation part just missing. Sort of a header that you can just read(?). Idk if it played a role in compilation, probably not. But some commercial libraries packaged them as well. Here, look at this random repo: https://github.com/keskival/turbo-pascal-experiments/tree/ma... -- few int files at the end of a list.

This page mentions a few ints without any context: https://comp.lang.pascal.borland.narkive.com/1B3WeJkX/rebuil...

This guy seems to package ints for documentation purposes: https://www.wrotniak.net/hplx/lxtpgr.html

Man this is nostalgic... T-T