A system design based on the use of a stored program on‐line computer is presented here. The system is used as an associative radiation analyzer. The channel capacity of the system is 20 bits (one million channel analyzer). The data storage program is based on a threaded list (tree) algorithm. The number of different events which will be measured during a particular experiment can be assigned for each experiment. The count capacity is 4096 counts per channel, but can be extended. Two alternatives are discussed, depending on whether a fast or medium speed computer is used. The mean input rates are 5000 or 1000 events per second alternatively. In both cases the resolution between two events is determined mainly by the analogue‐to‐digital converters used. There is a good flicker‐free display on the CRT. The display can be in map, isometric, or curve form. The display format (grid, unblanking, etc.) as well as the experimental conditions are under typewriter control.