The bitwise NOT (
~) operand is applied to a single operand.
NOT 0 = 1
NOT 1 = 0
So the not 10101010 becomes 01010101
There are two bit shift operators, the left shift operator << and the right shift operator >>
Generally the left shift operator syntax is :
variable << number_of_bits
and the right shift operator syntax is :
variable >> number_of_bits
The left shift operator shifts the bits to x positions to the left filling the last positions with x zeros .
y = 10101010
x = y << 1 //The resulting x should be x = 01010100
Another example XXXXXXXX << 5 = XXX00000
The right shift operator shifts the bits to x positions to the right filling the first positions with x zeros (most of the times) .
y = 10101010 >> 1 gives 01010101
Another example XXXXXXXX >> 2 = 00XXXXXX
Attention : when you shift
x right by
y bits (
x >> y), and the highest bit in
x is a 1, the filled bits depend on the exact data type of
x is of type
int, the highest bit is the sign bit, determining whether
x is negative or not.
int x = -16; // binary: 1111 1111 1111 0000 //(the negative sign is the highest bit set to 1) int y = x >> 3; // binary: 1111 1111 1111 1110
This behavior, called sign extension, is often not the behavior we want.
Instead, generally we want zeros to be shifted in from the left. To resolve this problem we just have to typecast the int value into a
unsigned int expression :
int x = -16; // binary: 1111 1111 1111 0000 int y = (unsigned int)x >> 3; // typecast int x into unsigned int. // binary: 0001 1111 1111 1110 In the next page we will see a real example in order to understand the bitwise operators