Q. What is Computer? Describe the functioning of computer with its block
diagram?
Ans:-
Definition:- A computer is a fast electronic device,
processing the Input data according to the Instructions given by the
Programmer/User and provides the desired information as an output.
or
It
is an electronic, data processing machine that receives the input from some
specific input devices, performs process, and produce output on some specific
output devices.
A Computer System or its Architecture consists of
following three elements:-
(1) Input Unit
(2) Output Unit
(3) Central Processing Unit
Input Unit:- Data and Instructions play an important role
in the working of computer without data and instructions no computation can
take place.
This is successful carried out by unit. It establishes a connection between user and
the computer system.
Input Unit is a unit though which communicates with the
computer. It is a translator between the
user the computer. It converts the given
into a computer acceptable form.
The most common of Input devices keyboard, which
resembles a typewriter. The help of a
keyboard, the user types data and instruction.
The other commonly Input devices are mouse, magnetic ink character
reader, magnetic tape, magnetic disk, optical mark reader and optical character
reader.
Input devices are
divided into two categories:-
Text Input Devices
Cursor Control Devices
·
In text input
devices the mainly used keyboard.
·
Cursor control
devices are mouse, joystick, scanner etc.
In brief, the following
functions are performed by the input unit:-
·
It accepts
(reads) data from user.
·
It converts the
instructions and data into computer acceptable form.
·
It passes the
converted instructions and data to the computer for processing.
Output Unit:-
Since computers work with binary code, the results produced are also in
binary form the basic function of the output unit therefore is to convert these
results into human readable form before providing the output through various
output devices like terminals, printers etc.
Output device can be classified into two types:-
(1)
Hard Copy Devices
(2)
Soft Copy Devices
Hard Copy
Devices:- These are those devices that
provide the output in permanent form. User can't change them and we can see them without the help of any machine. These devices are printers, plotters etc.
Soft Copy Devices:-
This comes in category when power is switched off, information are lost
information is on display till power is ON. We can make change in this and we cant able to access them without the help of any machine. Visual display unit(Screen) comes under this category. This unit is based for displaying results,
which are produced after processing of data.
In brief, the functions of the Output units are:-
·
To accept the
results processed by CPU which are in coded form.
·
To convert coded
results to human acceptable form.
·
To produce the
results to users.
Central Processing Unit:- The main brain of a computer system s the
central processing unit (CPU). The data
and instructions that are entered into the computer system are fed into the CPU
before the final results are displayed on the Output Unit. The CPU stores the data and instructions,
does all the calculations and problem solving, and also controls the functions
of all other units.
The CPU consists of the following Units:-
(1)
Memory Unit or
storage Unit
(2)
Arithmetic &
Logical Unit (ALU)
(3)
Control Unit
Memory
Unit:- The data and instructions that
are entered into the computer system with the help of input units must be
stored inside the computer before processing starts. Also the results produced by the computer
after processing must be stored inside the computer. The memory unit is responsible for storing
data, instructions and results. The
memory unit consists of a large number of cells, each capable of storing one
unit of information (word). The cells
are also called storage locations.
Memory Unit has four major logical areas:-
Input
Storage Area:- The Input does not
straight away go to the processor. It is
first stored in this area till the processor asks for it.
Working
Storage Area:- Working Storage Area is
like a sheet of scratch paper. When the
data is being processed, there are some intermediate results that are not
required as Output but are required to obtain the Output. Such results are stored in working storage
area.
Input Storage Area:- The final output don’t take by the output
devices immediately until they are ready to receive it. Thus an ‘output storage area’ holds the
finished results until they are released on the output device.
Program Storage Area:-
The primary storage also contains a program storage area. The instructions for data manipulation are
stored in this area.
Following are the main functions of memory unit:-
(1) It stores data and instructions received from the
input unit before processing starts.
(2) It stores the intermediate result of processing.
(3) It stores the final results of processing, before
these results are sent to output unit.
Arithmetic & Logical Unit:- This unit performs all the basic arithmetic
operations like addition, subtraction, multiplication, division and also
logical operations such as comparison of numbers etc. the ALU is responsible for actual execution
of instructions during processing operation.
The data and instructions that are stored in memory unit are transferred
into ALU for processing when needed and transferred back to memory when
processing is over. After the completion
of processing, the final results are stored in memory before sent to the output
unit. ALU also consist a number of small
storage locations, termed as registers.
These registers are of very small capacity and contains the data and
instructions which are to be executed next.
Following are the main functions of ALU:-
·
It operates on
data available in main memory.
· It caries out all
arithmetic operations like addition, subtraction, multiplication and division.
·
It caries out all
logic operations like comparison, selection and merging of data
·
After processing
the data, it sends back the processed data to main memory.
Control Unit:-
The control Unit in every computer is the supervising element. It does not perform any processing but acts
as a central control system for all other components of a computer system. This unit maintains the exact sequence in
which the instructions are to be executed and directs the operations of the entire
computer system. It co-ordinates all the
activities of various elements of computer system skill. It is termed as heart of computer as in
controls all hardware operation.
Functions of control unit are:-
·
It gives command
to transfer data from the input device to memory and from memory to arithmetic
& Logical Unit.
·
It transfers the
results from memory to Output Unit.
·
It stores the
program in memory, takes instruction one by one, interprets them and issue
appropriate signals to the other units of computer to the other units of
computer to execute them.
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