Question

Is there any difference between signed and unsigned variables on bitwise operations?
For example,when dealing with unsigned numbers:
AND 00000111, 00001101
will result 00000101.

But what would happen when dealing with signed numbers?

Était-ce utile?

La solution

Assuming 2's complement is used for signed numbers, operations that care about signedness (ie they are different for the signed and unsigned interpretation of a bitstring) are:

  • division
  • modulo
  • right shift
  • comparisons (except equality)
  • double-width multiplication (rare outside of assembly)

Operations for which signedness is irrelevant are:

  • addition
  • subtraction
  • negation (-x means ~x + 1)
  • bitwise and
  • bitwise or
  • bitwise xor
  • bitwise not (~x means -x - 1)
  • left shift
  • multiplication
  • comparison (equality only)

Autres conseils

Unsigned and signed numbers are an interpretation of a bitstring. The AND operator doesn't have that notion and works on the single bits. The result will be the same in any way.

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