adder

The puff adder, from Africa and western Arabia, grows up to 1.6 m/5 ft long. Puff adders often bask in the sun during the day and, if disturbed, make a loud hissing or puffing sound, hence their name.

The common adder, or viper, is widely distributed in Europe as far east as Siberia. It is a short, sturdy snake that lives on the ground. Being slow-moving, adders do not chase prey, but wait in a concealed position to ambush lizards, mice, voles, shrews, and frogs.

European venomous snake, the common viper Vipera berus. Growing on average to about 60 cm/24 in in length, it has a thick body, a triangular head, with a characteristic V-shaped mark and, often, zigzag markings along the back. It feeds on small mammals and lizards. The puff adder Bitis arietans is a large, yellowish, thick-bodied viper up to 1.6 m/5 ft long, living in Africa and Arabia.

adder

Electronic circuit in a computer or calculator that carries out the process of adding two binary numbers. A separate adder is needed for each pair of binary bits to be added. Such circuits are essential components of a computer's arithmetic and logic unit (ALU).