In compressed Fib objects variables are numbered and represented as natural numbers. In this, the first variables values in the Fib object are reserved for the input variables. Therefore, at this point for the variables only the number of input variables is interesting. For this a 64 bit natural number is stored at this location, which contains the number of input variables. After the field for the number of input variables () follow values, each, in ther order, for the default value of the input variable . The number of bits and the encoding of the default value of is determined by the domain of the input variable .
The input variable field is padded with 0 bits to a full byte.