Computer Dictionary/binary coded decimal
number is expressed as a sequence of decimal digits and then each decimal digit is encoded as a four-bit binary number (a nibble). E.g. decimal 92 would be encoded as the eight-bit sequence 1001 0010.
In some cases, the right-most nibble contains the sign (positive or negative).
It is easier to convert decimal numbers to and from BCD than binary and, though BCD is often converted to binary for arithmetic processing, it is possible to build hardware that operates directly on BCD.
[Do calculators use BCD?]