Arithmetic and Logical Unit





An Arithmetic and Logical Unit (ALU) is one of the core components of all
Central Processing Units. It is capable of calculating the results of a wide
variety of common computations. The most common available operations are the
integer arithmetic operations of addition, subtraction, and multiplication,
the bitwise logic operations of AND, NOT, OR, and XOR, and various shift
operations. Typically, a standard ALU does not handle integer division nor
any floating point operations. For these calculations a separate component,
such as a divider or Floating Point Unit (FPU), is often used, although it
is also possible that a microcode program may use the ALU to emulate these
operations.

The ALU takes as inputs the data to be operated on and a code from the
control unit indicating which operation to perform, and for output provides
the result of the computation. In some designs it may also take as input and
output a set of condition codes, which can be used to indicate cases such as
carry-in or carry-out, overflow, or other statuses.