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arithmetic logic unit (ALU)

The two most important components of the central processing unit (CPU) are the arithmetic unit and the controlunit (CU). While the control unit processes the instructions from the instruction register and controls the instruction cycles in the central processing unit (CPU), the arithmetic logic unit is responsible for arithmetic and logical operations. This is why arithmetic logic units are also called arithmetic logic

units (ALU). However, an arithmetic logic unit does not necessarily have to consist of only one ALU component, but can consist of several ALUs. An arithmetic logic unit, also called an operation unit, can perform all mathematical operations

of dual arithmetic

, such as addition, subtraction, multiplication and division, andthe AND gate can perform the AND

function,the OR gate can perform the OR function and the NOT gate can perform the NOT

function. In addition, the arithmetic unit can execute comparisons and shift instructions. The arithmetic unit processes the commands it receives from the control unit.

Basic structure of a

Basic structure of a

calculator The structure of an arithmetic unit comprises one or more adding units, half add ers or full adders, the control unit, accumulators and registers. The accumulators function as fast memory elements in which the operands for the operations and the intermediate results are stored. They are connected to the main memory via the data bus

. Thedata bus is the part of the system bus

over which thedata

and operands are transferred to the accumulators and memory registers. Depending on the concept, the intermediate results are also stored in the registers.

For the mathematical and logical operations the arithmetic unit needs two operands. One is transferred from the working memory via the data bus and temporarily stored in the accumulator. After the mathematical operation the intermediate result is stored again in the accumulator.

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Englisch: arithmetic logic unit - ALU
Updated at: 05.07.2019
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