This format holds numeric data items in computer storage in pure binary two's complement representation. In this format, number values are held in radix of 2 where each computer bit in the representation starting from the right (least-significant) end represents the presence or absence of an increasingly significant power of 2 in that value. Negative numbers are represented by complementing (inverting all the bit values of) their positive counterpart, and then adding one to the whole. Storage requirements depend on the number of "9"s in the PICTURE clause, and whether the numeric data item is signed or unsigned (see the topics The PICTURE Clause, The SIGN Clause and The USAGE Clause); also your COBOL system assigns storage for COMPUTATIONAL items in one of two modes; byte-storage and word-storage. Byte-storage is the default storage-assignment mode for this COBOL implementation.