Built-in features coding language

I am curios to know in which coding language are the built-in features, like the help system, image editor, exporter.
Is there anywhere a list (cause I wasn’t able to find it) or maybe somebody could write it here?
My curiosity is based on me being a hobby programmer.
Thanks for taking time to read my post!

Start here. I know LO is mostly build with C++ and Java.

Thanks a lot for the answer! I was able to find all the source code from there.