logical shift

programming (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 bitstring or a sequence of bit fields, whereas arithmeticshift is appropriate when treating it as a binary number.

The word to be shifted is usually stored in a register, or

possibly in memory.

(1996-07-02)