Page 20 - CA 165 ver 1.0 Class 9
P. 20

Processing Device


                  A CPU (Central Processing Unit) is also known as the ‘Brain of a Computer’. As it appears, it is a hardware
                  component, but it is  also  an important functional component of a computer system. It does all the
                  processing, calculations and comparisons at a rapid speed. Its speed is measured
                  in higher units of hertz (hz) i.e. 9 MHz. It takes information from the input unit
                  or memory and processes it as per the given instructions. Processing includes
                  calculations, comparisons, decision making, etc.
                  Some versions of processors are Pentium series, Dual Core, Core 2 Duo, Athlon,
                  IBM Cyrix, Core-i3, Core-i5, Core-i7, AMD Ex Series, etc.

                  Functional Elements of a CPU

                  The functional elements of a CPU can be divided into three parts:
                  l    Arithmetic Logic Unit  (ALU)

                  l    Control Unit (CU)

                  l    Memory Unit (MU)

                                                           INSTRUCTIONS
                           CONTROL UNIT (CU)
                                                                                    MEMORY UNIT  (MU)          INPUT/OUTPUT  UNIT





                           ARITHMETIC LOGIC
                               UNIT (ALU)                       DATA



                  Arithmetic Logic Unit (ALU)

                  An  ALU performs mathematical  calculations  (addition,  subtraction,  multiplication, division, etc.)  and
                  logical comparisons (greater than(>), less than(<), equal to (=), not equal to(!=), etc.). ‘Logical Operation’
                  refers to a comparison between two phrases that results in ‘TRUE’ or ‘FALSE’ value. It receives the coded
                  data and manipulates them to produce information in machine code and then send to the Control Unit.

                  Control Unit (CU)
                  A control unit co-ordinates and directs the operation of the hardware devices. It also co-ordinates the
                  flow and execution of the data and instructions, that are fed into the computer’s memory. CU functions
                  in a F-D-E-S (Fetch-Decode-Execute-Store) cycle. It fetches the instruction and data from the memory
                  unit & decodes them and passes to the ALU for further processing. It also directs the ALU to execute the
                  instructions and performs the required operations on the data.

                  Memory Unit (MU)

                  A memory unit or main storage or the internal storage stores the data, instructions, intermediate and the
                  final results that are ready for the output. All instructions or data are stored in the memory unit before
                  being used by the ALU or the CU.



                   18     Touchpad Computer Applications-IX
   15   16   17   18   19   20   21   22   23   24   25