1. A floating-point data operating unit comprising: a first register for storing data expressed according to a floating-point representation having a variable-length exponent part; a second register for storing data of a fixed-length exponent part; a third register for storing data of a fixed-length mantissa part; means connected to said first register for detecting the length of a string comprising 0s or 1s in a first part of said variable-length exponent part to establish the boundary between said variable-length exponent part and a mantissa part following said variable-length exponent part; means connected to said first register and said detecting means for transferring bits, forming a second part of said variable-length exponent part succeeding said first part and having a length dependent upon said detected length, from said first register to said second register; and means connected to said first register and said detecting means for transferring data which remains in said first register, following said bit transfer from said first register to said second register, to a third register, whereby the data in said first register is subdivided into an exponent part and a mantissa part.