In most countries a copyright work need to be something substantial. You can not copyright single machine instructions. It needs to be a combination that is uni

In most countries a copyright work need to be something substantial. You can not copyright single machine instructions. It needs to be a combination that is unique. And just the instructions are not copyrightable, you cant for example copyright a recepy. But you can copyright a book of recepies. So if you make a program with many instructions put togheter you automatically get copyright. And if someone steals parts of your code it will be difficult to claim the copyright if those parts are used to create a new program. But if the new program is based on your program, for example a fork, or most of the code comes from your program its derative work.