Addition and subtraction of binary digits
Two's complement

See google: Two's Complement

Fragment:


  Two's complement is a mathematical operation on binary numbers, best
  known for its role in computing as a method of signed number
  representation. For this reason, it is the most important example of a
  radix complement.
  
  The two's complement of an N-bit number is defined as its complement
  with respect to 2N. For instance, for the three-bit number 010, the
  two's complement is 110, because 010 + 110 = 1000.


Truth Table

Also called Karnaugh Diagram

See google: Truth Table


  A truth table is a mathematical table used in logic—specifically in
  connection with Boolean algebra, boolean functions, and propositional
  calculus—which sets out the functional values of logical expressions
  on each of their functional arguments, that is, for each combination
  of values taken by their logical variables (Enderton, 2001). In
  particular, truth tables can be used to show whether a propositional
  expression is true for all legitimate input values, that is, logically
  valid.


You also might have a look at Karnaugh Maps.