Abstract: A selective calling display radio pager has a memory which is configured to store a plurality of received messages for later retrieval so that the amount of messages which can be stored is limited by one of first and second memory availability factors depending on the length of each of the received messages. A controller determines one of the first and second memory availability factors which is more accurate early warning against possible depletion of the memory than the other and displays it on a graphic alarm indicator along with a display of a message retrieved from the memory. Specifically, the controller determines the ratio of a sum of messages which can be received at a given time to the maximum number of messages which can be stored and the ratio of a sum of message segments which can be received at said given time to the maximum number of such message segments which can be stored, and provides a display of the smaller ratio on the graphic alarm indicator.