definition of alu

The ALU or arithmetic logic unit consists of a digital circuit that allows arimetic and logical operations between two numbers.

ALU comes from English and is an acronym for Arithmetic Logic Unit. In Spanish, the logical arithmetic unit would be a kind of circuit that has the ability to calculate operations such as addition, subtraction or others such as NOT and XOR.

An ALU can be found in all types of electronic circuits and devices. For example, in a digital wristwatch that allows the addition of a second constantly. But also and in quantity in a complex modern microprocessor circuit. Other examples are found in graphics, sound or video cards, high definition TV sets, and CD players.

In 1945 John P. Eckert and John W. Mauchly brought this concept to life. Later, John von Neumann would publish a report on this, explaining the need for an ALU for the use of a computer in basic mathematical operations.

Typically, an arithmetic logic unit is composed of an operational circuit, an input register, an accumulator register, and a state register. These entities allow the correct functioning of the ALU and, for example, are responsible for the resolution of arithmetic operations of integers, logical operations of bits, operations of bit shifting and other more complex ones. The latter include, for example, calculating the square root, emulating a coprocessor and many others.

Another circuit similar to that of a unit of this type is the FPU or Floating Point Unit, which performs arithmetic operations but for numbers in floating point representation, which are more complex and sophisticated.

The schematic of an ALU generally includes A and B as operands, R as output, F as input of the control unit, and D as state of the output.

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