A data processing apparatus of a basic input/output system (BIOS) is provided. The data processing apparatus includes a BIOS unit, a share memory and a control unit. The BIOS unit writes command data into the share memory, wherein the command data includes identification data stored in an identification field. The control unit reads and performs the command data according to the identification data in the identification field. After the command data is performed, the control unit writes returned data into the share memory for the BIOS unit to read the returned data, wherein the returned data includes the execution result of the command data performed by the control unit and also includes the identification data.