ELECTRONIC CONTROL SYSTEM, STORAGE MEDIUM STORING DATA STRUCTURE OF SOFTWARE PACKAGE, AND STORAGE MEDIUM STORING COMPUTER PROGRAM

An electronic control system includes: a master controller that: receives an update program and an update information file including information related to a program update; and transfers the update information file and the update program; a sub-controller that: writes an update program into a first memory; and receives the update information file and the update program from the master controller; and a specific update execution unit that: stores specific update information related to a program update for a second memory; and writes an update program into the second memory. The sub-controller controls the specific update execution unit to write, according to the specific update information, an update program of a firmware into the second memory when the update information file indicates that the program update includes an update of the firmware.