what are the softwares used to test the circuit design? For example, to see if a circuit works, if it works with certain or different components and component values, and values of each component is drawing.
Most people use a spice simulator to test their designs. There are also some other higher level "logic only" simulators that are designed primarily for measuring timing and operation in digital circuits.
I've used circuitmaker you can download a trial version of it at **broken link removed** it runs using a SPICE engine. Also available is Proteus I think you can also get a demo or a cheaper version of it try http://www.labcenter.co.uk/index.html