PROGRAMMABLE CONTROLLER

PROBLEM TO BE SOLVED: To provide a programmable controller of a system in which, under a situation in which a need for program protection is becoming extremely high, as shown in a case where a user program of a programmable controller, which contains a knowhow of a manufacturing process, is not disclosed to unauthorized persons, a password in a hardware-form is required so as not to be easily broken so that program protection may be reinforced, unlike a conventional programmable controller in which protection using a software-form password is common and in the mainstream so that there is a security problem that if all sorts of passwords are input, the password is broken.SOLUTION: In a programmable controller, I/O modules for a programmable controller, having different functions, are arbitrarily mounted on a plurality of slots; combination information on a mounted arrangement of the mounted I/O modules is set as a password; and in response to an instruction of reading a program from a programming tool, the program can be disclosed when a password and the mounted arrangement of the I/O modules coincide with each other.