Arithmetic and Logic Unit (ALU)

•  The ALU contains the circuitry to perform the arithmetic operations like adds, subtracts, multiplies, devices and does comparisons on integer (whole number) and real numbers/operands (with decimal points).
• These comparisons are basically less than, greater than, equal to, greater  than or equal to.
• The object of most instructions that use comparisons is to determine which instructions should be executed next.
• ALU contains registers, which are special purpose temporary storage locations.
• Accumulator is one of such register, which is used to store intermediate results obtained during any arithmetical computations.
• Final result is also obtained in accumulator from where they can be transferred to memory. 
• The ALU controls the speed of calculations.