ones' complement

Wiktionary

1. n. computing The number obtained by subtracting a given n-digit binary number from (which yields the same result as the logical complement).
2. n. computing The convention by which bit patterns with high bit 0 represent positive numbers from 0 to directly, while bit patterns with high bit 1 represent negative numbers from 0 to , n being the word size of the machine, and the numeric complement of a number is its ones' complement.