1. A robot control system provided in a machining system comprising a robot and a machine tool, the robot control system comprising: a robot controller controlling the robot; a portable teach pendant connected to said robot controller; and a communication network adapted to connect said robot controller to a machine tool controller controlling the machine tool; wherein said teach pendant comprises a display section configured to display information relating to the robot and the machine tool; and wherein said robot controller comprises a processing section configured to obtain information relating to the machine tool from the machine tool controller through said communication network, make said display section of said teach pendant display a machine tool-related screen in accordance with a given screen program, and make said machine tool-related screen of said display section of said teach pendant display said information, as obtained, relating to the machine tool.