Block diagram of computer:
A computer can process data, pictures, sound and graphics.
They can solve highly complicated problems quickly and accurately.
Ø Input Unit: Computers need to
receive data and instruction in order to solve any problem. Therefore we need to input the
data and instructions into the computers. The input unit consists of one or
more input devices. Keyboard is the one of the most commonly used input device.
Other commonly used input devices are the mouse, floppy disk drive, magnetic tape,
etc. All the input devices perform the following functions. • Accept the data
and instructions from the outside world. • Convert it to a form that the
computer can understand. • Supply the converted data to the computer system for
further processing.
Ø Storage Unit: The storage unit of the
computer holds data and instructions that are entered through the input unit,
before they are processed. It preserves the intermediate and final results
before these are sent to the output devices. It also saves the data for the
later use. The various storage devices of a computer system are divided into
two categories.
Ø a. Primary Storage: Stores and provides
very fast. This memory is generally used to hold the program being currently
executed in the computer, the data being received from the input unit, the
intermediate and final results of the program. The primary memory is temporary
in nature. The data is lost, when the computer is switched off. In order to
store the data permanently, the data has to be transferred to the secondary
memory. The cost of the primary storage is more compared to the secondary
storage. Therefore most computers have limited primary storage capacity.
Ø b. Secondary Storage: Secondary storage is
used like an archive. It stores several programs, documents, data bases etc.
The programs that you run on the computer are first transferred to the primary
memory before it is actually run. Whenever the results are saved, again they
get stored in the secondary memory. The secondary memory is slower and cheaper
than the primary memory. Some of the commonly used secondary memory devices are
Hard disk, CD, etc.
Ø Output Unit: The output unit of a
computer provides the information and results of a computation to outside
world. Printers, Visual Display Unit (VDU) are the commonly used output
devices. Other commonly used output devices are floppy disk drive, hard disk
drive, and magnetic tape drive.
Ø Arithmetic Logical Unit: All calculations
are performed in the Arithmetic Logic Unit (ALU )
of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition,
subtraction, multiplication, division, etc and does logic operations via, >,
<, =, ‘etc. Whenever calculations are required, the control unit transfers
the data from storage unit to ALU
once the computations are done, the results are transferred to the storage unit
by the control unit and then it is send to the output unit for displaying
results.
Ø Control Unit: It controls all other
units in the computer. The control unit instructs the input unit, where to
store the data after receiving it from the user. It controls the flow of data
and instructions from the storage unit to ALU .
It also controls the flow of results from the ALU
to the storage unit. The control unit is generally referred as the central
nervous system of the computer that control and synchronizes its working.
Central Processing Unit:
The control unit and ALU
of the computer are together known as the Central Processing Unit (CPU).The CPU
is like brain performs the following functions:
•It performs all calculations. •It takes all decisions. •It
controls all units of the computer.
A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron,
Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core, and AMD
etc.
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