
One's Complement is a particular assignment of bit patterns
to numbers. For example, in the case of 3-bit binary numbers, we have
the assignments shown in Table
G.2.
Table G.2:
Three-bit one's-complement binary fixed-point numbers.
Binary |
Decimal |
000 |
0 |
001 |
1 |
010 |
2 |
011 |
3 |
100 |
-3 |
101 |
-2 |
110 |
-1 |
111 |
-0 |
|
In general,

-bit numbers are assigned to binary counter values in
the ``obvious way'' as integers from 0 to

, and then the
negative numbers are assigned in reverse order, as shown in the
example.
The term ``one's complement'' refers to the fact that negating a number in
this format is accomplished by simply
complementing the bit pattern
(inverting each bit).
Note that there are two representations for zero (all 0s and all 1s). This
is inconvenient when testing if a number is equal to zero. For this
reason, one's complement is generally not used.
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