# How to find decimal of a number in One's Complement form?

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1. Aug 30, 2015

### Aristotle

1. The problem statement, all variables and given/known data
Assume the number
https://www.physicsforums.com/tel:1111111 [Broken]
Is in one's complement form, what is its decimal values?

2. Relevant equations

2^7 + 2^6 + 2^5 + 2^4 + 2^3 + 2^2 + 2^1 + 2^0

1 in first sign bit indicates negative
0 in first sign bit indicates positive

3. The attempt at a solution

The first thing I did to solve this problem is that we know that 1111111 is already in 1's complement form and so I inverse the bits and got 0000000. Noticing that there is a 1 in the first sign bit of the binary 1111111 that is in 1s complement form, I included a 'negative' to the decimal 0. From the inverse number 0000000... Is simply added to equal 0...and got -0.

is this the correct method in approaching this? any guidance would be appreciated! Thank you

Last edited by a moderator: May 7, 2017
2. Aug 30, 2015

### rcgldr

In one's complement, all 1's is negative zero. Some processors will automatically convert all 1's to all 0's in their results.