A ternary computer (also called trinary), is a computer that uses ternary instead of binary logic.
There are two forms of ternary:
The first form replaces powers of 2 with powers of 3. For example:
decimal -> binary -> ternary
1 -> 1 -> 1
2 -> 10 -> 2
3 -> 11 -> 10
11 -> 1011 -> 102
The second form uses the values (-1, 0, 1) instead of (0, 1, 2), but still uses base 2.
This form of ternary, called balanced ternary, is useful because is allows the easy representation of negative numbers. In typical binary, negative numbers are represented by changing a sign bit. Those are not needed in balanced ternary:
7 -> 111 -> 111
-7 -> 100000111 -> (-1)(-1)(-1)