Arithmetic-logic section in computer system:

The   arithmetic-logic section performs arithmetic   operations, such subtraction, addition, multiplication, and division. Throughout internal logic capability, it tests several conditions encountered for the duration of processing and takes action based on the outcome. At no time does processing take place in the storage section. Data can be transferred back and forth amongst these 2 sections many times before processing is completed.

The control section does not carry out actual processing operations on the data. Control section instructs the input device on when to begin and stop transferring data to the input storage area. It also commands the output device when to begin and stop receiving data from the output storage area.