Orcad is a systematic simulation tool, including not only circuit simulation, but also various levels of simulation tools such as circuit board design. Capture is a circuit drawing software. When simulation is used in capture, capture will call pspice for simulation. Pspice was originally written by a team in Berkeley to simulate various circuits, but at first it could only be simulated by netlist. There is no graphical interface, which is unfriendly to use. Later, orcad added a graphical interface, namely capture, after obtaining the copyright. When capturing the simulation, it will use pspice to call its kernel, and the general relationship is like this.