Digital Electronic Circuits
Digital electronics are electronics systems that use digital signals. Digital electronics are represented by Boolean algebra and is used in computers, mobile phones, and other products. Electronic circuits can usually be categorized as analog, digital, or mixed-signal.
An electronic circuit is an electrical circuit that contains electronic devices such as transistors or capacitors. In digital electronic circuits, electric signals take on values to show logic and number values that process information.

Reference :http://www.hyperphysics.phy-astr.gsu.edu
Reference :http://www.wikimedia.org