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Editorial Team
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Asked: 2026-05-27T06:48:04+00:00

I have learned how to work with 80×86 assembler, so in bit-wise shift operation,

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I have learned how to work with 80×86 assembler, so in bit-wise shift operation, I faced a problem with SAL and SHL usage. I means the difference between lines of code as follow :

MOV X, 0AAH
SAL X, 4

MOV X, 0AAH
SHL X, 4

When we should use SHL and when use SAL? What is the difference of them?

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1 Answer

  1. Editorial Team

    According to this, they are the same:

    The shift arithmetic left (SAL) and shift logical left (SHL)
    instructions perform the same operation; they shift the bits in the
    destination operand to the left (toward more significant bit
    locations). For each shift count, the most significant bit of the
    destination operand is shifted into the CF flag, and the least
    significant bit is cleared (see Figure 7-7 in the Intel®64 and IA-32
    Architectures Software Developer’sManual, Volume 1).

    Both were probably included just for completeness since there is a distinction for right-shifts.

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