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Logical right shift differs from arithmetic right shift. Thus, many languages have different operators for them. For example, in Java and JavaScript, the logical right shift operator is >>>, but the arithmetic right shift operator is >>. (Java has only one left shift operator (<<), because left shift via logic and arithmetic have the same effect.)
The two basic types are the arithmetic left shift and the arithmetic right shift. For binary numbers it is a bitwise operation that shifts all of the bits of its operand; every bit in the operand is simply moved a given number of bit positions, and the vacant bit-positions are filled in.
When performed on a negative value in a signed type, the result is technically implementation-defined (compiler dependent), [5] however most compilers will perform an arithmetic shift, causing the blank to be filled with the set sign bit of the left operand. Right shift can be used to divide a bit pattern by 2 as shown:
Java adds the operator ">>>" to perform logical right shifts, but since the logical and arithmetic left-shift operations are identical for signed integer, there is no "<<<" operator in Java. More details of Java shift operators: [10] The operators << (left shift), >> (signed right shift), and >>> (unsigned right shift) are called the shift ...
Arithmetic shift: the operand is treated as a two's complement integer, meaning that the most significant bit is a "sign" bit and is preserved. Logical shift: a logic zero is shifted into the operand. This is used to shift unsigned integers.
It can however in theory also be used to implement unary operations, such as logical shift left, in cases where limited by a fixed amount (e.g. for address generation unit). One way to implement a barrel shifter is as a sequence of multiplexers where the output of one multiplexer is connected to the input of the next multiplexer in a way that ...
This method is mathematically correct and has the advantage that a small CPU may perform the multiplication by using the shift and add features of its arithmetic logic unit rather than a specialized circuit. The method is slow, however, as it involves many intermediate additions. These additions are time-consuming.
This section is supposed to be about arithmetic shift vs multiplication, but then talks about arithmetic shift vs logical shift. As far as I know, arithmetic and logical left shift are identical operations, so I'm not sure what this section is talking about.