Screen data is generated by a screen generating processor (74) of a control host computer (7) and transmitted to a programmable display apparatus (5). In accordance with the screen data, the programmable display apparatus (5) inquires a PLC (3) or the like about a state of a device (21), so as to update the display or transmit a control instruction depending on an input result. On the other hand, a control host computer (7) has a public server section (77) to transmit to a client apparatus (9) via the Internet an applet, which is generated by a compiler (76) compiling the screen data. The client apparatus (9) executes the applet to transmit to the public server section (77) an or the control instruction inquiry similar to those the programmable display apparatus (5) makes. In this way, the display is updated in accordance with a response. This realizes a control system, which allows a display content of the programmable display apparatus (5) to be remotely checked from a remote area remote from the programmable display apparatus (5), without newly generating a display screen.