Arithmetic logic unit (ALU) In computing, an arithmetic logic unit (ALU) is a combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on floating point numbers. It is a fundamental building block of many types of computing circuits, including the central processing unit (CPU) of computers, FPUs, and graphics processing units (GPUs). The inputs to an ALU are the data to be operated on, called operands, and a code indicating the operation to be performed; the ALU's output is the result of the performed operation. In many designs, the ALU also has status inputs or outputs, or both, which convey information about a previous operation or the current operation, respectively, between the ALU and external status registers. An ALU has a variety of input and output nets, which are the electrical conductors used to convey digital signals between the ALU and external circuitry. When an ALU is operating, external circuits apply signals to the ALU inputs and, in response, the ALU produces and conveys signals to external circuitry via its outputs. An arithmetic unit, or ALU, enables computers to perform mathematical operations on binary numbers. They can be found at the heart of every digital computer and are one of the most important parts of a CPU (Central Processing Unit). An ALU consists of three types of functional parts: storage registers, operations logic, and sequencing logic. ?Therefore ALU stands for Arithmetic Logic Unit (Option 4).