What is it or what is it called when software can modify and build itself from source?

This is a mind bug that's been eating my soul for a couple weeks now and I can't search for it because I don't know what to search for. There's a specific word for it (i think) but I can't remember it.

What is a software/SDK or what is it called when you can edit/work/develop the software & compile new working binaries for that program from an already built older version of the program?

EDIT: I didn't word my question very well, example:

You write the code in C++ in "software_a_v1.0.0" and then compile it to create "software_a_v1.1.0" and use it to again write more code in C++ to create "software_a_v1.2.0". An independent, self-contained software development loop.