Canonical signed digit
In computing canonical-signed-digit (CSD) is a number system for encoding a floating-point value in a two's complement representation. This encoding contains 33% fewer non-zeros than the two's complement form, leading to efficient implementations of add/subtract networks in hardwired Digital signal processing.
The representation uses a sequence of one or more of the symbols, -1, 0, +1 (alternatively -, 0 or +) with each position possibly representing the addition or subtraction of a power of 2. For instance 23 is represented as +0-00-, which expands to or
CSD is obtained by transforming every sequence of zero followed by ones (011...1) into + followed by zeros and the least significant bit by - (+0....0-).
As an example: the number 7 has a two's complement representation 0111