Decimal adder with end around carry

A system for implementing a binary code decimal (BCD) arithmetic add/subtract operation on two BCD numbers independent of which BCD number is of a greater magnitude, the system comprising:

• an arithmetic logic to implement a method comprising:
• performing a BCD arithmetic add/subtract operation on a first BCD number A and a second BCD number B, wherein the first BCD number A has a first magnitude and the second BCD number B has a second magnitude, wherein the first magnitude is one of greater than, equal to, and less than the second magnitude, the performing comprising:
• generating carry information based on the first and second BCD numbers;
• in parallel to the generation of the carry information, computing a sum and two differences of the first and second BCD numbers;
• and
• selecting a final result in signed magnitude form from the sum and two differences based on the carry information and a control signal indicating one of an add operation and a subtract operation without any post processing steps.

A computer-implemented method for implementing a binary code decimal (BCD) arithmetic add/subtract operation on two BCD numbers independent of which BCD number is of a greater magnitude, the method comprising:

• performing, by an arithmetic logic of a computer, a BCD arithmetic add/subtract operation on a first BCD number A and a second BCD number B, wherein the first BCD number A has a first magnitude and the second BCD number B has a second magnitude, wherein the first magnitude is one of greater than, equal to, and less than the second magnitude, the performing comprising:
• generating carry information based on the first and second BCD numbers;
• in parallel to the generation of the carry information, computing a sum and two differences of the first and second BCD numbers;
• and
• selecting a final result in signed magnitude form from sum and two differences based on the carry information and a control signal indicating one of an add operation and a subtract operation without any post processing steps.