Details of some transportable microcomputer programs developed for the non-iterative computation of electron trajectories in image intensifier tubes are presented. For the computation of the cylindrically symmetric electrostatic field, the integral equation method and a new version of the dynamic programming method for rotationally symmetric systems are used. The program for electron trajectories eliminates the numerical integration errors associated with classical integration techniques. The computational efficiency of the programs on microcomputers supported by the UCSD p-system is discussed. Improvement of the efficiency and generalization to general electromagnetic systems are briefly indicated.