C Programming - Bitwise Operators - Discussion

The Answer should be A. Because we can perform addition as well as subtraction using bitwise XOR.

Please explain the answer in detail.

Whoever wrote this should swot up of course you can do bitwise addition and subtraction.

unsigned int myAdd(unsigned int a, unsigned int b)
{
unsigned int carry = a & b;
unsigned int result = a ^ b;
while(carry != 0)
{
unsigned int shiftedcarry = carry << 1;
carry = result & shiftedcarry;
result ^= shiftedcarry;
}
return result;
}

A big circuit inside the computer is made up of adder and subtracters which can perform all the operations like addition, multiplication, subtraction and division so how it can't be performed Dmitri has given good example above.

If bitwise operators can't be used for addition or subtraction, why can the hardware do it? It uses boolean operations on individual bits...
Also try the following function (which does addition with bitwise operators):


int bitadd(int x, int y)
{
int z = 0, c;
do {
z = x ^ y;
c = (x & y) << 1;
x = z;
y = c;
} while (c);
return z;
}

Bitwise operators can be used for multiplication and division only.