In a digital computer controlled system it is possible to monitor several variables almost at the same time and control the system according to the most critical one. This is called a sampled-data control system. The purpose of the paper is to demonstrate how to handle such a problem. A simplified reactor system including neutron kinetics and fuel and cooling medium kinetics with a simple control circuit is examined. It is assumed that the reactor has a great number of cooling channels, and it is necessary to check the exit temperatures of the cooling medium as the maximum value is the limiting factor. Sampling is performed to accomplish this. The temperatures are scanned and a comparison is made between the value stored in the memory and the point being measured. The higher of the two values remains in the one word memory. After checking all the temperatures, a pulse representing the temperature of the hottest channel is sent through the sampler to the regulator and the memory is cleared. A suitable method to study the stability is the z transform analysis. The procedures and logic followed are outlined here. First, the system is defined in the terms of Laplace transformation. Then the solving of the sampled system problem by the z transform theory is shown. A digital computer program is developed. The results of several calculations show the importance of choosing the right parameter combinations.