Multiple events may actually occur at the same point in time. Two or more independent events may just happen to be fired at the same time instant, or additional events may be fired at the time instant as a consequence of handling one of the events at that time instant. In the example below different event handlers A, B, C and D occur in a special order according to the declaration order.
Since the when-statements in the algorithm section are sequential, pre(x) will not be updated until reaching the end of the algorithm section.