Slide 17 of 27 - The ADDLIB() function is used to open libraries. However, it will fail if the specified library has already been opened by another script, so you need to check that it's not open first. If it's already open, it's available for use without any further action. - The SHOW() function checks for the presence of the specified string (2nd parameter) in the specified list (1st parameter). In this case, 'L' or 'LIBS' means libraries open to ARexx.