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# Negative numbers shown in bits

Dale DeMott
Ranch Hand
Posts: 515
Okay.. so here's an easy one for you. How can I represent -4 in bits. Any good rule of thumb would be great so its easy to remember how to do it later. I understand the positive 4. Thats easy. 0100
Thanks
-Dale
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What's this H2SO4 doing in my fridge?? ( thud )

Cindy Glass
"The Hood"
Sheriff
Posts: 8521

Dave Vick
Ranch Hand
Posts: 3244
Dale
To find the negative value of a number you use the twos compliment:
1. take the positive number and flip all the bits (turn 1's into 0's and 0's into 1)
2. add 1 to the result
so for your example of -4
4 is
00000000 00000000 00000000 00000100
flip the bits
1111111 11111111 11111111 11111011
1111111 11111111 11111111 11111100
this is -4 in binary.

hope that helps
Dave

Dale DeMott
Ranch Hand
Posts: 515
Thanks
Dale

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What's this H2SO4 doing in my fridge?? ( thud )