An arithmetic logic unit is also capable of “binary shifting”. That is moving the binary digits in the accumulator to the left or right a given number of spaces. In effect this either multiplies or divides the number by a factor of two, but in reality it is used to access and change individual bits in a series. This is useful when the binary stored is not really a number, but represents something else. This often finds uses in low level programming because micro-controllers and microprocessors rely on the values of individual bits for particular operations. This video provides a brief introduction.