A computer-based data acquisition, display and processing system for flow cytometers has been developed. The Los Alamos Cell Analysis (LACEL) programs and electronic hardware provide the capability to acquire list mode or histogram data for up to eight parameters and control bidirectional sorting based on up to four parameters for each direction. The programs described in this paper also enable the display of single parameter and bivariate histograms and the graphical manipulation of the list mode data. The electronic hardware is described in a companion paper.