Use the LINK or LINKX macro to pass control between load modules and to provide for return of control. You can also pass control using branch, branch and link, branch and save, or branch and save and set mode instructions or the CALL macro. However, when you pass control in this manner, you must protect against multiple uses of non-reusable or serially reusable modules. You must also be careful to enter the routine in the proper addressing mode. The following paragraphs discuss the requirements for passing control with return in each case.