Abstract: An adder, operating on the carry-select principle, provides for the transmission of two carry signals (c-0, c-1) and incorporates only one half-added (HA1) for the formation of the sum signal. Every adder stage (AS) of the adder is composed of an initial adder cell (AZA) and of a plurality of normal adder cells (AZN). The initial adder cell (AZA) forms a sum signal (s) from the supplied operand bits (a, b) upon employment of one of the two carry signals (c-0, c-1) and of a selection signal (e), which signals are permanently set. The normal adder cells (AZN) generate a sum signal from the operand bits supplied to them upon employment of one of two carry signals selected by the selection signal (e) supplied from the next-lower adder cell. The initial adder cell (AZA) and the normal adder cells (ANS) differ in their carry networks (CSA, CSN) which employ Manchester carry chains for the generation or transmission of the two carry signals (c-0, c-1).