In this paper, we study some operational quality measures of thek-out-of-nsystems. Performance of these systems is characterized by a quality (output) function that is decreasing in the absence of components' failures. Moreover, it decreases (downward jump) with each failure of a component in a system as well. We employ the point processes approach for description of the corresponding failure process and derivation of the main results. Expectations (unconditional and conditional on survival) and variability for the system's quality function are derived and analyzed. The corresponding 'future quality process' is defined and described. Some illustrative examples are presented.