storing negative numbers

Question

In this code below

int main()
{
int  a = -1;
printf("%d",a>>1);
return 0;
}

Why it is giving output -1.

Answer 1

bit-shifting is defined only on unsigned types, for signed types it is implementation-defined. And this is a useful refinement by R..

Strictly speaking, it is defined for signed types whenever the value is positive and the result does not overflow, and right shift is implementation-defined for negative values. Left shift, on the other hand, is undefined for negative values

┌───┬──────────────┬──────────────────────────────────┬────────────────────────┐
│   │ Unsigned     │ Signed, positive                 │ Signed, negative       │
├───┼──────────────┼──────────────────────────────────┼────────────────────────┤
│<< │ well-defined │ well-defined, except on overflow │ undefined behaviour    │
│>> │ well-defined │ well-defined                     │ implementation-defined │
└───┴──────────────┴──────────────────────────────────┴────────────────────────┘

Answer 2

Because -1 is 1111111...111 in binary. a>>1 operation will "sign extend" the sign bit, so you get 1111111...111 again.