This preview shows page 1. Sign up to view the full content.
Unformatted text preview: ystem is the place where the actual
execution of the instructions takes place during the processing operation. To be more
precise, calculations are performed and all comparisons (decisions) are made in the ALU.
The data and instructions, stored in the primary storage prior to processing, are
transferred as and when needed to the ALU where processing takes place. No processing
is done in the primary storage unit. Intermediate results generated in the ALU are
temporarily transferred back to the primary storage until needed at a later time. Data may
thus move from primary storage to ALU and back again to storage many times before the
processing is over. After the completion of processing, the final results, which are stored
in the storage unit, are released to an output device.
The type and number of arithmetic and logic operations that a computer can perform is
determined by the engineering design of the ALU. However, almost all ALUs are
designed to perform the four basic arithmetic operations (add, subtract, multiply, and
divide), and logic operations or comparisons such as less than, equal to, and greater than.
How does the input device know that it is time for it to feed data into the storage unit?
How does the ALU know what should be done with the data once they are received? And
how is it that only the final results are sent to the output device and not the intermediate
results? All this is possible because of the control unit of the computer system. By
selecting, interpreting, and seeing to the execution of the program instructions, the
control unit is able to maintain order and direct the operation of the entire system.
Although, it does not perform any actual processing on the data, the control unit acts as a central nervous system for the other components of the computer system. It manages and
coordinates the entire computer system. It obtains instructions from the program stored in
main memory, interprets the instructions, and issues signals that cause other units of the
system to execute them.
CENTRAL PROCESSING UNIT
The control un...
View Full Document
This document was uploaded on 04/07/2014.
- Spring '14