PROGRAM UPDATE SYSTEM, CONTROL SYSTEM, MOBILE BODY, PROGRAM UPDATE METHOD, RECORDING MEDIUM

A program update system updating programs comprising: a first control device executing a program stored in the primary storage area thereof; a second control device executing a program stored in the primary storage area thereof; a program storage temporarily storing an acquired program; a program acquirer preferentially acquiring and storing into the program storage a first program to be stored in the first control device, and acquiring and storing into the program storage a second program to be stored in the second control device; and an update unit storing the first program stored in the program storage into the primary storage area of the first control device, storing the second program stored in the program storage into the primary storage area of the second control device, and switching the primary storage area and the secondary storage area of the first control device.