Unsigned and signed shift:logical shift and arithmetic shift

In C, we usually use left shift and right shift operation << and >> to operate multiple / divide to variable with power of 2,ex: 4<<2  = 16

But when we use the signed variable and the shift operation we must consider the singed bit.See the below example code.

Since the C language support the arithmetic left shift and logic right shift,  we must consider the signed bit to  avoid some bug in code.



Ref:
     1.Logical Vs. Arithmetic Shift
     2.C语言中的逻辑右移和算术左移