1. A system for off-line programming of multiple interacting robots, comprising: at least one handling robot holding a part and at least one process robot having a tool for processing the part; a computer for off-line programming and verification of program codes for multiple interacting robots, wherein the computer is configured to define a virtual robot cell including the handling robot, the process robot and the part, incorporate parameters defined as constraints to be taken into consideration in the control of the multiple robots, the parameters including constraints enabling the at least one handling robot to move the part at the same time as the at least one process robot simultaneously perform active processing on the part, the parameters including a penalty value assigned to an active joint of each of the at least one handling robot and the at least one process robot such that movement of at least one joint of the at least one handling robot closest to the part is used more than other joints of the at least one handling robot, and movement of the axes of the process robot closest to the tool processing the part is used more than the other axes of the at least one process robot, create at least one path for the holding robot based on the parameters, create at least one path for the process robot defined in relation to geometric features of said part defined in the virtual robot cell based on a trajectory defined in relation to said part, and said parameters, automatically generate program code based on the created paths, and verify the created paths in a simulation executing the program code; and a robot controller for controlling the robots, which controller is connected to the computer to receive a download of the program code for execution.