Computer Dictionary of Information Technology

logical shift

(Either shift left logical or shift right logical) Machine-level operations available on nearly all processors which move each bit in a word one or more bit positions in the given direction. A left shift moves the bits to more significant positions (like multiplying by two), a right shift moves them to less significant positions (like dividing by two). The comparison with multiplication and division breaks down in certain circumstances - a logical shift may discard bits that are shifted off either end of the word and does not preserve the sign of the word (positive or negative).

Logical shift is approriate when treating the word as a bit string or a sequence of bit fields, whereas arithmetic shift is appropriate when treating it as a binary number. The word to be shifted is usually stored in a register, or possibly in memory.