Javascript Tilde & Two's complement

Question

Two\'s complement method - generates -(x + 1).

for example when JavaScript encounters the Tilde he uses this method:

~5 = -(5+1) = -6         


        

Answer 1

First of all, you need to realize that ~ is the bitwise flip operator, which is not the same as the negate operator -. ~ does only do the bitwise flipping, but the negate operator - does bitwise flipping and add one (for integers).

As you've explained, if yo want to go from a postive number n to -n using the two complement method you bitwise flip/not n and add 1. ~n is just the bit-wise not meaning that ~n=-n-1.

For instance:

5               = 0000 0101
Flipped (~5)    = 1111 1010

So, which number does 1111 1010 represent? Since the first digit is a 1 we know it's a negative value. To find which value, do

-(flip(1111 1010) + 1) =
-(0000 0101 + 1)
-(0000 0110) =
-6

Answer 2

Two's complement method - generates -(x + 1).

Simply put, two's complement does not generate -(x + 1). One's complement does (i.e., ~ / bitwise NOT / flipping the bits).

Two's compliment (flip the bits, add 1) is the (-0 averse) operation/encoding we use to express a negative number in pure bits (and derive it therefrom). Two's complement of x will generate -x.

~5 is nothing more than flipping the bits 0000 0101 to 1111 1010.

To determine the value of 1111 1010, we flip back to 0000 0101 and add 1: 0000 0110 (-6).

Answer 3

~ is the Bitwise NOT operator (only inverts the bits of its operand).

For a positive number n,

~n + 1 = -n

Answer 4

Tild(~) -

it is just flip(n). I.e. ~5 = flip(5). In java script numbers are always 64 bit signed. let us take Just 8 bit for reference,

 5==> 0000 0101 
~5 ==> filp(0000 0101)
~5 ==> 1111 1010 ==> -6 

2' complement -

It's filp(n) + 1.

5 ==> 0000 0101
2's complement of 5 ==> flip(0000 0101) + 0000 0001
2's complement of 5 ==> 1111 1010 + 000 0001
2's complement of 5 ==> 1111 1011

Answer 5

~5 = -(5 + 1) = -6

so far so good. However, ~ is not the two's complement, it's the binary inversion operator.

5     = 0000 0101
flip  : 1111 1010

which is -6

does that make it clear?