Bibi-binary express any number, it suffices to enumerate the (hexadecimal) digits that make it up. For example: the number written as "2000" in base ten, which translates to "7D0" in conventionally-written hexadecimal, would in Bibi-binary be spoken aloud as "BIDAHO". Contrary to the numeric conventions used in modern computers, the bibi-binary system represents negative numbers using one's complement, rather than two's complement. Thus: and their sum is written as "1 1111" (one of two representations of zero in this system; zero can also be written as "0 0000"). On modern machines, in classic binary notation, −7 would be written 1 1001,
Combinatorial number system of a set "S" is a subset of "S" with "k" (distinct) elements. The main purpose of the combinatorial number system is to provide a representation, each by a single number, of all formula_1 possible "k"-combinations of a set "S" of "n" elements. Choosing, for any "n", } as such a set, it can be arranged that the representation of a given "k"-combination "C" is independent of the value of "n" (although "n" must of course be sufficiently large); in other words considering "C" as a subset of a larger set by increasing "n" will not change the number that