A data processing system having a central processing unit (CPU) capable of performing binary and decimal arithmetic software instructions is disclosed. The CPU includes a microprocessor which executes the binary arithmetic software instructions under firmware control. Also disclosed is apparatus utilizing...http://www.google.de/patents/US4638450?utm_source=gb-gplus-sharePatent US4638450 - Equal nine apparatus for supporting absolute value subtracts on decimal operands of unequal length
