A production system in which a control device configured to control at least one industrial device and a host control device that is capable of controlling the control device are communicably connected, wherein the host control device includes: - a data storage part in which a control program for controlling the control device is stored, the control program specifying an execution order of processes to be executed by the control device using the industrial device, - a register part that has a register that is allocated for controlling the control device and includes a command area, - an operation control part configured to ∘ control, based on the control program and variables referenced by the control program, the control device, ∘ write the variables for requesting execution of a process in the command area by executing the control program, wherein a command requesting a program selection and a program name are written as the variables in the command area, and - a transmission part that is configured to transmit the variables written in the command area to the control device by executing the control program; and the control device includes: - a communication storage part in which the variables received from the host control device are written, - data storage part in which multiple programs are stored, wherein the control device is capable of executing the multiple programs, and the multiple programs include for each of the processes a corresponding program defining individual procedures, and - an execution part configured to: ∘ select, based on the command, a program of the program name from the multiple programs, and ∘ execute a process, instructed by the host control device, based on the variables written in the communication storage part and the selected program. the host control device includes: - a data storage part in which a control program for controlling the control device is stored, the control program specifying an execution order of processes to be executed by the control device using the industrial device, - a register part that has a register that is allocated for controlling the control device and includes a command area, - an operation control part configured to ∘ control, based on the control program and variables referenced by the control program, the control device, ∘ write the variables for requesting execution of a process in the command area by executing the control program, wherein a command requesting a program selection and a program name are written as the variables in the command area, and - a transmission part that is configured to transmit the variables written in the command area to the control device by executing the control program; and - a data storage part in which a control program for controlling the control device is stored, the control program specifying an execution order of processes to be executed by the control device using the industrial device, - a register part that has a register that is allocated for controlling the control device and includes a command area, - an operation control part configured to ∘ control, based on the control program and variables referenced by the control program, the control device, ∘ write the variables for requesting execution of a process in the command area by executing the control program, wherein a command requesting a program selection and a program name are written as the variables in the command area, and ∘ control, based on the control program and variables referenced by the control program, the control device, ∘ write the variables for requesting execution of a process in the command area by executing the control program, wherein a command requesting a program selection and a program name are written as the variables in the command area, and - a transmission part that is configured to transmit the variables written in the command area to the control device by executing the control program; and the control device includes: - a communication storage part in which the variables received from the host control device are written, - data storage part in which multiple programs are stored, wherein the control device is capable of executing the multiple programs, and the multiple programs include for each of the processes a corresponding program defining individual procedures, and - an execution part configured to: ∘ select, based on the command, a program of the program name from the multiple programs, and ∘ execute a process, instructed by the host control device, based on the variables written in the communication storage part and the selected program. - a communication storage part in which the variables received from the host control device are written, - data storage part in which multiple programs are stored, wherein the control device is capable of executing the multiple programs, and the multiple programs include for each of the processes a corresponding program defining individual procedures, and - an execution part configured to: ∘ select, based on the command, a program of the program name from the multiple programs, and ∘ execute a process, instructed by the host control device, based on the variables written in the communication storage part and the selected program. ∘ select, based on the command, a program of the program name from the multiple programs, and ∘ execute a process, instructed by the host control device, based on the variables written in the communication storage part and the selected program.