what is arithmetic logic unit

The arithmetic/logic unit (ALU) is the computer's calculator. It performs all arithmetic operations, in addition to decision making functions. A few current processors use multiple ALUs to attain high processing speeds. However, most microprocessors have a single ALU.

Arithmetic operations include addition, subtraction, multiplication, and division. The data operated on can be stored in various forms: the binary, BCD, EBCDIC and ASCII representations.

The ALU makes use of temporary storage areas referred to as registers. Data to be arithmetically manipulated are copied from memory and placed in registers for processing. Upon completion of the arithmetic operation, the result can be transferred from the register to memory, freeing the register for the next arithmetic operation. In addition to registers, the ALU uses one or more adders, devices that actually add, subtract, multiply, or divide the binary digits.

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