For the additive group of 2n elements, the arithmetic logic unit (ALU) consists of a straight binary adder that does not distinguish the sign of the operands or result. However, in twos-complement notation, the sign is implicit in the most significant bit S. The ALU produces an n-bit result together with a carry bit C representing the n+1th bit. For timestamp calculations, the C bit is in effect the least significant bit of the era number of the datestamp, but most often it is implicit in the calculation of offset.