functions is to deallocate memory reserves that are no longer required a further aspect of the invention is a process that ensures that the real time criteria stipulated for the control process are adhered to whenever program modifications are carried out as a rule control programs are run cyclically the real time criteria are defined by the execution intervals of the programs in which the inputs are read the control programs are run and the outputs are written the adherence to the real time criteria is achieved by subdividing the implementation of program modifications into a preparatory phase and a critical phase as has already been mentioned above in order to implement the program modification successfully no program commands of the control program may be executed in either phase the preparatory phase which entails practically all necessary measures for implementing a program modification approx 99 can be interrupted and repeated any number of times in the event of the preparatory phase being interrupted by the execution of a program command this can be initiated again at any time the critical phase includes the activation of the new program for reasons of consistency activation must take place for all program objects simultaneously this explains why this process cannot be interrupted using the present invention the time required for both phases can be determined precisely the.