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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:
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.
Left arithmetic shift Right arithmetic shift. In an arithmetic shift, the bits that are shifted out of either end are discarded. In a left arithmetic shift, zeros are shifted in on the right; in a right arithmetic shift, the sign bit (the MSB in two's complement) is shifted in on the left, thus preserving the sign of the operand.
The B bus can be enabled by just one register at a time, since the transfer of data from 2 registers at the same time, would make this data inconsistent. In contrast, the C bus can be enabled by more than 1 register at the same time; as a matter of fact, the current value present in the C bus can be written to more than 1 register without problems.
The very fastest shifters are implemented as full crossbars, in a manner similar to the 4-bit shifter depicted above, only larger. These incur the least delay, with the output always a single gate delay behind the input to be shifted (after allowing the small time needed for the shift count decoder to settle; this penalty, however, is only incurred when the shift count changes).
In all single-bit shift operations, the bit shifted out of the operand appears on carry-out; the value of the bit shifted into the operand depends on the type of 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.
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The programming languages C, C++, and Go, however, have only one right shift operator, >>. Most C and C++ implementations, and Go, choose which right shift to perform depending on the type of integer being shifted: signed integers are shifted using the arithmetic shift, and unsigned integers are shifted using the logical shift.