"To obtain the code of -x from the code of x... flip all the bits of x and add 1 to the result."
when I try to do this to zero in my ALU, it doesn't work, I always end up back at zero
Example
0000
Not
1111
Inc
0000
The extra one overflows. Am I doing something wrong? The book also says "Bit-wise negation of zero gives the 2’s complement code of -1.", so negating zero should end up with -1.
-0 and 0 are the same number so they have the same binary representation.
The confusion is the phrase "bit-wise negation" which is the Boolean Not operation applied to each bit. Wherever you read bit-wise negation, think not.
The ALU example you quote is explaining how the -1 is generated in the ALU for the x-1 operation.
The nx and ny control signals are "not x" and "not y". With zy=1 and ny=1, the y input to the adder is not(0). This is -1.
Locked
