Electronics is the science of how to control electric energy, energy in which the electrons have a fundamental role. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive electrical components and interconnection technologies. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements; such a circuit is described as an electronic circuit.
Spice is a program developed by the EE Department at the University of California at Berkeley for computer simulation of analog circuits. In its original form you tell Spice what elements are in the circuit (resistors, capacitors, etc.), and then enter the circuit diagram as an ASCII file showing what nodes each element is connected to. Every node is assigned a number, and there is always a ground node, which is Number 0.
You then tell Spice what information you want -- bias conditions, frequency response, and/or transient response. Spice does the circuit analysis and puts out an ASCII file with the information. Using Spice is not very intuitive to use because the input is an ASCII file rather than a circuit diagram, and the output is another ASCII file rather than a graph. Several companies have developed graphical user interfaces for Spice, which make it much easier to use.
One of the most popular is PSpice.
Altium Designer is an electronic design automation software package for printed circuit board, FPGA and embedded software design, and associated library and release management automation. It is developed and marketed by Altium Limited of Australia.
OrCAD is a proprietary software tool suite used primarily for electronic design automation (EDA). The software is used mainly by electronic design engineers and electronic technicians to create electronic schematics and electronic prints for manufacturing printed circuit boards.