Abstract: A program-controlled communication installation is composed of at least a digital computer system having a computer core (processor) administered by a multi-tasking operating system and having a system memory wherein a plurality of program modules are stored. Each of the program modules serves the purpose of realizing a defined function of the communication installation. A function can only be executed in that the appertaining program module is handled by the computer core. Since a plurality of functions usually pend for execution, the executable program modules are noted in a process list from which the operating system respectively selects the program module having the highest priority and allocates it to the computer core for execution.