The Arithmetic and Logic Unit (ALU) is the fundamental building block of the Central Processing Unit (CPU) of digital computers. It is an integrated circuit designed to perform arithmetic and logic operations on the data stored in the memory of a computer.
The ALU forms the basic foundation of the central processing unit, and performs majority of the calculations and logical comparisons necessary to complete instructions of the instruction set. It is the main component of the CPU that is responsible for interpreting and executing computer instructions and transferring data between other components of the computer.
The ALU takes binary data stored in memory as input and then performs the necessary calculations and logical comparisons before returning a resultant value as output. The arithmetic operations include addition, subtraction, multiplication and division, while the logic operations consist of bitwise operations (such as comparisons and shift operations) and logic functions such as AND, OR, and XOR.
The ALU is designed to process a specific instruction set, and consequently varies from processor to processor. The particular arithmetic and logic instructions that an ALU is capable of performing dictate the capabilities of the processor and its ability to run software.
An ALU typically has several registers, the most common being the accumulator and the flag register. The accumulator is a register used to store the output of arithmetic or logical calculations. The flag register is a set of bits used to store the results of operations performed by the ALU, such as whether the result is negative, whether it produces a carry or borrow, or if any zero bits were generated..
Overall, the ALU is the most functional component of a computer’s CPU. Modern ALUs are much more sophisticated and significantly faster than those in earlier computers, helping to make the computer as fast and efficient as possible.
