What are RPG COPYBOOKS anyway?

Copybooks are a very simple way of reproducing the same code into many programs: a copybook is a source member containing a section of code that can be inserted/copied into any other source member at compilation time. The main idea behind RPG Copybooks is reusability.

Think of a copybook as a source member that contains a common re-usable code component that that you dont want to compile but want to include in the actual programs that use it at compile time.