Page 9 - DCAP105_WORKSHOP_ON_COMPUTER_HARDWARE_AND_NETWORK
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Unit 1: Introduction to Hardware and Software




          5.   Motherboard: Motherboard, also called as System Board, is the most important hardware  Notes
               component of a microcomputer. Motherboard is so called as all the other boards (printed
               circuit boards having chips or other electronic components) of the computer are connected
               to this board, hence it is like the mother of all other boards.
          Now we will discuss the components of computer hardware in detail.

          1.1.1 Central Processing Unit

          Central Processing Unit (CPU) is the main component or “brain” of a computer, which performs
          all the processing of input data. Its function is to fetch, examine and then execute the instructions
          stored in the main memory of a computer. In microcomputers, the CPU is built on a single chip
          or  Integerated  Circuit  (IC)  and  is  called  as  a  Microprocessor.  The  part  of  a  computer  (a
          microprocessor chip) that does most of the data processing, the CPU and the memory form the
          central part of a computer to which the peripherals are attached. The Central Processing Unit
          (CPU) is the part of a computer that interprets and carries out the instructions contained in the
          software.
          The CPU consists of the following distinct parts:

              Arithmetic Logic Unit (ALU): The arithmetic and logic unit of CPU is responsible for all
               arithmetic operations like addition, subtraction, multiplication and division as well as
               logical operations such as less than, equal to and greater than. Actually, all calculations
               and comparisons are performed in the arithmetic logic unit.
              Control Unit (CU): The control unit is responsible for controlling the transfer of data and
               instructions among other units of a computer. It is considered as the “Central Nervous
               System” of  computer, as  it manages and coordinates all the units of  the computer. It
               obtains the instructions from the memory, interprets them and directs the operation of the
               computer. It also performs the physical data transfer between memory and the peripheral
               device.
              Registers: Registers are small high speed circuits (memory locations) which are used to
               store  data,  instructions  and memory  addresses  (memory  location numbers),  when
               ALU performs arithmetic and logical operations. Registers can store one word of data
               (1 word = 2 bytes & 1 byte = 8 bits.) until it is overwritten by another word. Depending on
               the processor’s capability, the number and type of registers vary from one CPU to another.
               Registers  can be divided  into  six categories  viz. General  Purpose Registers,  Pointer
               Registers, Segment Registers, Index Registers, Flags Register  and Instruction  Pointer
               Register, depending upon their functions. The detailed functions of each and every register
               is beyond the scope of this book.
              Buses: Data is stored as a unit of eight bits (BIT stands for Binary Digit i.e. 0 or 1) in a
               register. Each bit is transferred from one register to another by means of a separate wire.
               This group of eight wires, which is used as a common way to transfer data between
               registers is known as a bus. In general terms, bus is a connection between two components
               to transmit signal between them. Bus can be of three major types viz. Data Bus, Control
               Bus and Address Bus. The data bus is used to move data, address bus to move address or
               memory location and control bus to send control signals between various components of
               a computer.
              Clock: Clock is another important component of CPU, which measures and allocates a
               fixed  time  slot for  processing each  and every  micro-operation  (smallest  functional
               operation). In simple terms, CPU is  allocated one or more  clock cycles to complete  a
               micro-operation. CPU executes the instructions in synchronization with the clock pulse.




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