Negative Numbers in Bits

[L Sol]

How do you calculate the following number is equal to -6?
1111 1111 1111 1111 1111 1111 1111 1010
Thanks!

[Richard Quist]

Originally posted by L Sol:
How do you calculate the following number is equal to -6?
1111 1111 1111 1111 1111 1111 1111 1010
Thanks!

Since negative numbers are represented in two's-complement form you need to

Flip all the bits

add one

restore the negative sign

original: 1111 1111 1111 1111 1111 1111 1111 1010
inverted: 0000 0000 0000 0000 0000 0000 0000 0101
add one: 0101
0001
----
0110 (which is 6 in base 10)
Restore negative sign: -6

[Serghei Jelauc]

Let say we have 1111 1101
Change all 1 and 0 vice versa: 0000 0010
0000 0010 = 2.
After it add 1: now have 3
and add "-" sign: -3
That's all.
Hope it halps

[Corey McGlone]

If you want more information regarding 2's complement, do a search over this forum - you'll find tons of good information.
Corey