Used by the routines at 5F1C and F5BE, and by command lists 0x00, 0x02, 0x04, 0x06, 0x08, 0x20, 0x22, 0x2E, 0x30, 0x32 and 0x34 to make a character do nothing. The RET instruction is located in ERIC's buffer at byte 0x24, which is otherwise unused.