The input/output block common extension (IOBE) specifies the type of channel program and its format, options that control the execution of the channel program and the level of ERP processing, and provides the anchor to the IEDB. The IOBE is an extension to the IOB and, like the IOB, provides for communication between the user of EXCP and the system. This control block is required for format-1 CCW channel programs and zHPF channel programs, but is optional for format-0 CCW channel programs. See Input/Output Block Common Extension (IOBE) Fields.