Downloadable computer software programs for use in the subject of engineering, namely, for reliability prediction (RP), thermal and stress derating analysis (SDTA), failure mode and effects analysis and criticality analysis (FMEA/FMECA), fault tree analysis (FTA), and test ability analysis of electronic and mechanical systems; downloadable computer software program for design error detection and stress analysis for electrical circuits; downloadable computer software program for detecting design errors during the design phase, before layout and production; downloadable computer software program add-on for an Electronic Design Automation (EDA) tool, namely, downloadable computer software program for electronic computer-aided design; downloadable computer software program for integrating design error detection with electrical stress, thermal, mean time between failure (MTBF) and service life predictions at the schematic level, before printed circuit board (PCB) layout and production