Functional Components of Computer

Functional Components:
The hardware of a computer system can be classified into the Central Processing Unit (CPU) and peripherals.
The heart of the computer is called CPU or Processor.

The CPU Performs:
I) Arithmetic Operations
II) Logical Operations
III) Input-Output Operations
IV) Internal data movements (moving data between various parts of storage)
V) Data manipulation

To perform these operations the CPU has various components:
a. Arithmetic-Logic Unit (ALU): It performs the actual calculations (addition, subtraction, division, multiplication) and comparison (equal to, greater, lesser, positive, negative, zero etc).
b. Control Unit (CU): It coordinates the operation of the hardware, the flow and execution of data and instructions that are fed into the memory or main storage via the CPU.

c. Memory Unit (Main Store): It holds data instructions (that are being interpreted and executed), intermediate results and final results ready for output. The data and instructions are passed from the main store into ALU, or to and from the storage devices under the control of the CU.
Within the CPU there are a number of high speeds, special purpose memory units called registers. These registers carry out critical functions in the execution of programmes.

A computer has four basic types of registers:
1) Accumulator register (ACC)
2) Store operand register (SOR)
3) Control register (CR)
4) Instruction address register (IAR).

Buses: The control unit and internal storage are linked together by sets of parallel electrical conducting lines called buses. The buses that carry data are called data buses. The retrieval of data from memory is carried by the memory address bus.

Peripheral Devices:
The peripheral devices can be classified as input devices, output devices and backing storage devices.

Input Devices allow the user to get data into the machine. A large range of input, devices are available, e.g. keyboard, mouse.

Output Devices are peripherals used to output results to the user. They include printers, plotters and VDUs (Visual Display Units).

Backing Storage Devices or the secondary storage devices are mainly hard disk, CDS, disk packs, floppy disks, and tapes used to store data and programmes permanently.

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