The two most important components of the central processing unit( CPU) are the arithmetic unit and the control unit( 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, and the 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 commands. The arithmetic unit processes the commands it receives from the control unit.
The structure of an arithmetic unit includes 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. The data bus is the part of the system bus over which the data 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 main memory via the data bus and temporarily stored in the accumulator. After the mathematical operation the intermediate result is stored again in the accumulator.