1. A COPYBOOK can contain some portion of your COBOL program.
For instance you have two programs: prog1 and prog2.
Both of these use a same set of working storage variables. Here, instead of using them twice in both programs, you can make a COPYBOOK ie another pgm/dataset letz say "progcpy", wch will only contain these working storage variables and nothing else.
This is called a working storage cpybook. You can incluse this "progcpy" in both of your pgms by using the statement: