bitwise not operator

Question

Why bitwise operation (~0); prints -1 ? In binary , not 0 should be 1 . why ?

Answer 1

It's binary inversion, and in second complement -1 is binary inversion of 0.

Answer 2

What you are actually saying is ~0x00000000 and that results in 0xFFFFFFFF. For a (signed) int in java, that means -1.

Answer 3

Because ~ is not binary inversion, it’s bitwise inversion. Binary inversion would be ! and can (in Java) only be applied to boolean values.

Answer 4

I think the real reason is that ~ is Two’s Complement.

Javascript designates the character tilde, ~, for the two’s complement, even though in most programming languages tilde represents a bit toggle for the one’s complement.

Answer 5

In standard binary encoding, 0 is all 0s, ~ is bitwise NOT. All 1s is (most often) -1 for signed integer types. So for a signed byte type:

0xFF = -1    // 1111 1111
0xFE = -2    // 1111 1110
...
0xF0 = -128  // 1000 0000
0x7F = 127   // 0111 1111
0x7E = 126   // 0111 1110
...
0x01 = 1     // 0000 0001
0x00 = 0     // 0000 0000

Answer 6

For 32 bit signed integer

~00000000000000000000000000000000=11111111111111111111111111111111 (which is -1)