~ operator in C

Question

The output of this program is -13. I have never fully understood ~ operator in C. Why does it give -13 as output? How to limit ~ operator to just 4 bits of a number?

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Answer 1

it's a bitwise operator (one's complement ) that works this way :

~00000101 // 5
=11111010 // 250

so the 1s become 0s and vise versa but in some cases the sign bit is activated and you'll get unexpected results