Bitwise operator x >> 1 and x >> 0 [duplicate]

Question

Possible Duplicates:
What do these operators do?
>> in javascript

Can somebody please explain the bitwise operator >> 1?

example:

65 >> 1 = 32

and also when >> 0

what does it achieve in this example:

var size = (Math.random() * 100 >> 0) + 20;

Answer 1

var size = (Math.random() * 100 >> 0) + 20;

>> 0 in the above example is used to eliminate the fractional portion, as follows:

1. Math.random() returns a number between 0 and 0.99999999...
2. This number multiplied by 100 gives you another number between 0 and 99.999999...
3. This number is right shifted 0 times. The number is implicitly cast to an integer for the shift operation; right shifting 0 times does not have any effect on the value of the resulting integer. You thus end up with an integer between 0 and 99. Note that you could have used the Math.floor() function instead of >> 0.
4. Add 20 to the integer, the result is an integer between 20 and 119.

Answer 2

Bitwise operator >> means shift right.
It moves the binary value to the right (and removes the right-most bit).

65 >> 1 in binary is:

1000001 >> 1 = 100000 = 32

It effectively divides the number into 2 and drops the remainder.