AbstractAn operational simulation is a collection of interrelating events. In order to code a simulation more easily for an electronic computer the events should be isolated, i.e., free from immediate interactions. Logical aid is used to determine cause‐effect relationships and eliminate impossible interactions from consideration. A timing model is set up, partitioning the events in time and space finely enough to insure their mutual exclusiveness. An automatic computer program is described that will compile mutually exclusive events, which may all be precoded as if occurring at one time and at one place. The program allows flexibility for adding, omitting, and replacing events or their parts, and for interrupting the simulation to allow human decisions to be incorporate