Question

    -5 / 2 = -2

    -5 >> 1 = -3

I learn from my teacher that >>1 divides the number by 2. It works on positive number but it does not work on negative numbers. Can someone explain to me??

Thanks

Answer 1

As BЈовић & mystical states, using bit shift operators on negative numbers is implementation defined.
The reason for this is C doesn’t distinguish between logical and arithmetic bit shifting.
(Arithmetic pads with the most significant bit, logical pads with 0’s)
for positive numbers this doesn’t matter, for both arithmetic and logical bit shifts would keep the most significant bit as a 0:
Arithmetic 5>>1
0000 0000 0000 0101 = 5
to
0000 0000 0000 0010 = 2

Logical 5>>1
0000 0000 0000 0101 = 5
to
0000 0000 0000 0010 = 2

however with a negative number (2’s comp)
Arithmetic -5>>1
1111 1111 1111 1011 = -5
to
1111 1111 1111 1101 = -3

Logical -5>>1
1111 1111 1111 1011 = -5
to
0111 1111 1111 1101 = 32,765

or at least, this is how i understand it