SMP/E is a tool for managing software installations and modifications on z/OS systems. It controls changes at the component level by selecting code versions to install, calling utilities to perform the installation, and maintaining records of changes in its consolidated software inventory database. SMP/E uses system modification packages called SYSMODs, which contain code updates and instructions, to modify software elements. The main SMP/E commands - RECEIVE, APPLY, and ACCEPT - place SYSMODs in libraries, select SYSMODs for installation, and install them to update the system software.