bitwise not operator

Question

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

Answer 1

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