Keywords are ALU, Overflow/Underflow, Two'sComplement(,and...)
ALU is is a part of the execution unit, a core component of all
CPUs.
ALUs are capable of calculating the results of a wide variety of basic arithmetical computations such as integer and floating point arithmetic operation(addition, subtraction, multiplication, and division), bitwise logic operation, and bit shitf operation. Therefore the inputs to the ALU are the data to be operated on (called operands) and a code from the control unit indicating which operation to perform. Its output is the result of the computation.--from
http://en.wikipedia.org/wiki/ALU
Two's complement is the most popular method of representing signed integers in computer science. It is also an operation of negation (converting positive to negative numbers or vice versa) in computers which represent negative numbers using two's complement. Its use is ubiquitous today because it doesn't require the addition and subtraction circuitry to examine the signs of the operands to determine whether to add or subtract, making it both simpler to implement and capable of easily handling higher precision arithmetic. Also, 0 has only a single representation, obviating the subtleties associated with negative zero (which is a problem in one's complement). --from
http://en.wikipedia.org/wiki/Two's_complement