Abstract: There is described a control device of a machine, an engineering system and a method for operating said control device. Said control device is used to control and/or regulate the machine and is used to carry out at least one user program which is used to at least perform one function, and said control device comprises a debug function. The functionality of the debug function is limited in large user programs due to the high complexity and the unclearness thereof. According to the invention, in order to improve said function, the user program comprises stop points for the debug function and said stop points can be activated and/or deactivated.